A+ Manual

A+ HARDWARE Exam 220-301 Covers 2003 A+ Objectives

IDENTIFYING, ADDING AND REMOVING SYSTEM COMPONENTS ............ 8 Inside the PC ........................................................................................ 8 1. Motherboard components .................................................................... 8 2. Different types of memory .................................................................... 9 3. Connectors, jumpers, and switches .................................................... 10 4. Devices and their connectors ............................................................. 11 5. Casing types and adapter cards ......................................................... 13 Summary ............................................................................................. 14 Power supplies, storage, and display devices ..................................... 15 1. Power supply characteristics .............................................................. 15 2. Different types of storage devices ...................................................... 15 3. Display devices ................................................................................. 19 Summary ............................................................................................. 20 System boards and power supply units ............................................... 22 1. Replacing system boards .................................................................. 22 2. Replacing power supplies and fans .................................................... 23 Summary ............................................................................................. 25 Installing storage devices ................................................................... 26 1. Installing and removing storage devices ............................................. 26 2. DVDs, tape drives, and removable storage ......................................... 29 Summary ............................................................................................. 31 Adding adapters and input devices ..................................................... 33 1. Adding and removing input devices .................................................... 33 2. Adding and removing adapters .......................................................... 34 Summary ............................................................................................. 35 1. Adding and removing input devices .................................................... 36 2. Adding and removing power sources .................................................. 37 Summary ............................................................................................. 39 Storage devices and adapters for portable systems ............................ 40 1. Installing and upgrading memory........................................................ 40 2. Installing storage devices .................................................................. 41 3. Installing PC cards ............................................................................ 42 Summary ............................................................................................. 43 DIAGNOSING AND TROUBLESHOOTING................................................ 45 Troubleshooting the system board ...................................................... 45 1. System board symptoms ................................................................... 45 2. Configuration and hardware checks ................................................... 47 3. Troubleshooting field replaceable units ............................................... 49 Summary ............................................................................................. 50 Power supply, port, and cable problems.............................................. 51 1. Troubleshooting the power supply unit................................................ 51 2. Port symptoms, basic and Windows checks ........................................ 52 3. Troubleshooting USB ports ................................................................ 54

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4. Troubleshooting infrared ports ........................................................... 56 5. Troubleshooting FireWire ports .......................................................... 56 Summary ............................................................................................. 57 Peripheral and display device problems .............................................. 59 1. Troubleshooting scanners and tape drives .......................................... 59 2. Troubleshooting input devices ............................................................ 61 3. Troubleshooting display devices ........................................................ 63 Summary ............................................................................................. 65 Networking, modem, and SCSI problems............................................. 66 1. Troubleshooting a NIC....................................................................... 66 2. Troubleshooting SCSI devices ........................................................... 68 3. Troubleshooting a modem ................................................................. 70 Summary ............................................................................................. 71 Resolving video and sound problems ................................................. 73 1. Troubleshooting a sound card ............................................................ 73 2. Troubleshooting video ....................................................................... 74 Summary ............................................................................................. 76 Troubleshooting storage and cooling devices ..................................... 77 1. Troubleshooting floppy disk drives ..................................................... 77 2. Troubleshooting HDDs, CD, and DVD drives ...................................... 79 3. Troubleshooting cooling systems ....................................................... 81 Summary ............................................................................................. 83 Troubleshooting notebook computers ................................................ 84 1. General troubleshooting procedures ................................................... 84 2. Troubleshooting power supplies ......................................................... 85 3. Troubleshooting devices .................................................................... 86 4. Troubleshooting drives ...................................................................... 87 5. Troubleshooting ports and sound systems .......................................... 88 Summary ............................................................................................. 90 Gathering information and troubleshooting ......................................... 92 1. Tools for diagnosis and repair ............................................................ 92 2. Information gathering ........................................................................ 94 3. Troubleshooting the boot process ...................................................... 94 4. Troubleshooting FRUs....................................................................... 95 Summary ............................................................................................. 96 PRINTERS, MAINTENANCE and SAFETY ISSUES ................................ 97 Printer technologies............................................................................ 97 1. Printer types and basic mechanics ..................................................... 97 2. Dot-matrix printers ............................................................................ 99 3. Ink-jet printers ................................................................................. 100 4. Laser printers ................................................................................. 100 5. Specialized printing technologies ..................................................... 102 Summary ........................................................................................... 102 Printer interfaces, options, and upgrades .......................................... 104 1. Printer interfaces ............................................................................. 104 2. Printer options and upgrades ........................................................... 106

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Summary ........................................................................................... 107 Troubleshooting printers .................................................................. 108 1. Troubleshooting ink-jet printers ........................................................ 108 2. Troubleshooting dot-matrix printers .................................................. 109 3. Troubleshooting laser printers .......................................................... 111 Summary ........................................................................................... 113 Cleaning and protecting hardware..................................................... 114 1. General preventive maintenance ...................................................... 114 2. Protecting hard drives and monitors ................................................. 116 3. Floppy disk drives and input devices ................................................ 117 4. Maintaining different types of printers ............................................... 118 Preventive maintenance plan ............................................................... 119 Summary ........................................................................................... 120 Maintaining the hard disk and UPS .................................................... 121 1. The Defrag utility ............................................................................. 121 2. The Chkdsk and ScanDisk utilities ................................................... 122 3. Surge suppressors and UPS ............................................................ 123 Summary ........................................................................................... 125 Safety and environmental measures ................................................. 126 Introduction ........................................................................................ 126 Electrostatic discharge (ESD) .............................................................. 126 Two types of damage .......................................................................... 126 Common causes of ESD ..................................................................... 126 Precautions against ESD..................................................................... 127 Grounding .......................................................................................... 127 Static shielding bags ........................................................................... 127 Anti-static spray and static-free carpeting ............................................. 127 Temperature regulation ....................................................................... 128 Installing humidifiers ........................................................................... 128 Precautions against high voltage ......................................................... 128 Shock hazards.................................................................................... 128 Metallic objects ................................................................................... 128 Liquids ............................................................................................... 129 Plugs and power cords ........................................................................ 129 Printers and the safety precautions ...................................................... 129 Safe disposal of computer components ................................................ 129 Disposal guidelines ............................................................................. 129 Material Safety Data Sheets ................................................................ 130 Monitors and power supply units .......................................................... 130 Ink cartridges...................................................................................... 130 Batteries ............................................................................................ 130 Chemical solvents and cans ................................................................ 130 Summary ........................................................................................... 131 MEMORY, MOTHERBOARDS and PROCESSORS ................................. 133 Memory types and form factors ......................................................... 133 1. Memory types ................................................................................. 133

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2. Calculating parity ............................................................................ 135 3. The different form factors of RAM..................................................... 136 4. Memory on the motherboard ............................................................ 138 Summary ........................................................................................... 140 Configurations and settings .............................................................. 141 1. The CMOS Setup utility ................................................................... 141 2. BIOS, chipset, and power management ............................................ 143 3. PnP, PCI, and peripherals settings ................................................... 145 Summary ........................................................................................... 147 Motherboard types and components ................................................. 149 1. Motherboard types, connectors, and ports ........................................ 149 2. USB, SCSI, and IEEE 1394 ............................................................. 151 3. Drive connections ........................................................................... 153 Summary ........................................................................................... 154 Processor sockets and CPU chips .................................................... 156 1. Early Pentium processors ................................................................ 156 2. Modern Pentium processors ............................................................ 157 3. Cloned processors .......................................................................... 159 4. Socket specifications and clock speeds ............................................ 160 Socket and slot specifications .............................................................. 160 5. CPU configuration ........................................................................... 164 Summary ........................................................................................... 165 Chipsets and bus architectures ............................................................ 166 1. Chipsets and bus speeds ................................................................ 166 2. Expansion slots............................................................................... 167 3. Local bus architectures .................................................................... 167 4. AGP slots ....................................................................................... 169 Table of expansion bus specifications .............................................. 170 Summary ........................................................................................... 170 BASIC NETWORKING........................................................................... 172 Types of network ports ..................................................................... 172 1. Standard I/O ports ........................................................................... 172 Typical AT and ATX I/O ports ............................................................ 174 2. Serial ports ..................................................................................... 174 3. Parallel ports .................................................................................. 176 4. USB, FireWire, and infrared ports..................................................... 177 Summary ........................................................................................... 179 Network cables ................................................................................. 180 1. Coaxial and UTP cabling ................................................................. 180 UTP cable categories ........................................................................ 181 2. Fiber-optic cabling ........................................................................... 181 Summary ........................................................................................... 182 Network types, topologies, and architecture ...................................... 183 1. Peer-to-peer and client/server networks............................................ 183 2. The characteristics of LAN topologies ............................................... 183 3. Characteristics of the Ethernet protocol ............................................ 185

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4. Token Ring and FDDI LANS ............................................................ 187 Summary ........................................................................................... 189 Network protocols and MAC/IP addressing ....................................... 190 1. Defining network protocols............................................................... 190 2. Addressing on a network ................................................................. 191 3. IP addresses and their characteristics .............................................. 193 Summary ........................................................................................... 195 Installing and configuring network cards........................................... 196 1. Installing a NIC ............................................................................... 196 2. Assigning a computer name............................................................. 197 3. Installing and configuring TCP/IP ..................................................... 198 Summary ........................................................................................... 199 Internet connectivity ......................................................................... 200 Introduction ........................................................................................ 200 Routers .............................................................................................. 200 Brouters ............................................................................................. 201 Communication technologies ............................................................... 201 Bandwidth .......................................................................................... 201 Common communications technologies ............................................... 202 Summary ........................................................................................... 204 System Resources and Installing and Configuring IDE and SCSI Devices ............................................................................................................ 206 IRQ, DMA, and I/O ports .................................................................... 206 1. Transferring data ............................................................................ 206 Interrupt request channels ................................................................... 209 Available DMA channels ..................................................................... 209 2. Onboard and system I/O methods .................................................... 210 Interrupt vectors ............................................................................... 210 Memory address map........................................................................ 211 3. Typical IRQ and I/O assignments ..................................................... 212 Summary ........................................................................................... 214 IDE types, connection, and configuration .......................................... 215 1. EIDE specifications and characteristics ............................................ 215 2. EIDE drive connection and configuration .......................................... 216 Summary ........................................................................................... 218 Physical connections and cabling ..................................................... 219 1. PIO modes, DMA modes, and Serial ATA ......................................... 219 Programmed input/output speeds ..................................................... 219 DMA modes ...................................................................................... 220 2. RAID levels .................................................................................... 221 Summary ........................................................................................... 222 SCSI types and termination ............................................................... 223 1. SCSI specifications ......................................................................... 223 2. Characteristics of SE, HVD, and LVD SCSI ...................................... 224 3. Termination of SCSI devices ............................................................ 225 Summary ........................................................................................... 227

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INSTALLING, CONFIGURING AND OPTIMIZING COMPUTERS ............... 228 Installing printers, monitors, and UPSs ............................................. 228 1. Installing a local printer .................................................................... 228 2. Installing video cards and monitors................................................... 230 3. Uninterruptible power supplies ......................................................... 231 Summary ........................................................................................... 232 Analog dial-up, DSL, and cable modems ........................................... 234 1. Installing analog dial-up modems ..................................................... 234 1. Installing analog dial-up modems ..................................................... 237 2. DSL and cable modems .................................................................. 240 Summary ........................................................................................... 241 Digital, infrared, and wireless devices and PDAs ............................... 243 1. Retrieving data from a digital camera ............................................... 243 2. Installing infrared transceivers .......................................................... 243 3. PDAs and wireless LAN standards ................................................... 244 Summary ........................................................................................... 246 Upgrading the system board ............................................................. 247 Introduction ........................................................................................ 247 Upgrading a motherboard.................................................................... 247 Upgrading components ....................................................................... 247 Microprocessor upgrades .................................................................... 247 BIOS upgrades ................................................................................... 249 Memory upgrades ............................................................................... 249 CMOS backup battery ......................................................................... 250 Power supply upgrades ....................................................................... 250 Summary ........................................................................................... 251 Upgrading adapter cards, hard drives, and laptops ........................... 253 1. Upgrading portable computers ......................................................... 253 2. Upgrading HDDs ............................................................................. 255 3. Upgrading adapters and cooling systems ......................................... 256 Summary ........................................................................................... 257

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IDENTIFYING, ADDING AND REMOVING SYSTEM COMPONENTS

Inside the PC 1. Motherboard components In a PC, the motherboard is a thin, flat piece of circuit board which contains the CPU and enables the other computer components to communicate with it. Different components use the following kinds of connectors on the motherboard:      

CPU socket RAM slots Power connections Expansion slots Drive connections External connectors

CPU socket The CPU socket is the physical connection between the CPU – also called the microprocessor – and the motherboard. Different CPUs use different socket types, and some CPUs are actually mounted vertically into slots, rather than sockets. RAM slots Random Access Memory (RAM) slots are long, thin slots, almost always colored black, with clips on the end. These clips secure the memory modules, mounted on circuit boards, that you place in the slots. Power connections The power connector on this type of motherboard is a single, 20-pin block, into which cables from an external power supply are attached. Expansion slots Small printed circuit boards – known as expansion cards, adapter cards, or simply cards – can be inserted into expansion slots. The cards enable communication between external devices and the motherboard. Drive connections The floppy disk drive (FDD) connector has 34 pins, whereas the hard disk drive (HDD) connector has 40 pins. You attach the FDD and HDD to the appropriate connectors via ribbon cables. External connectors External connectors allow connection to I/O devices, such as a keyboard, mouse, and printer.

Motherboards can include integrated circuits (ICs) , which are soldered directly onto the board rather than placed in a slot or socket. However, the slots and sockets on the motherboard make it easy to enhance the performance of your system. For example, you can insert an adapter card into one of the expansion slots to add extra functionality – network connectivity, for example.

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2. Different types of memory RAM is a type of memory that the CPU uses to temporarily hold data and instructions. However, the information stored in RAM is volatile – it is erased when you turn the PC off. RAM is measured in megabytes (MB). The average PC today has around 128 MB of RAM.

Note When used as a measure of the amount of memory, 1 MB is generally understood to mean 2 to the power of 20 – or 1,048,576 – bytes. RAM is available in the following different physical packages:   

DIMM SODIMM SIMM

DIMM The 168-pin dual inline memory module (DIMM) is currently the most common type of memory module used in PCs. SODIMM The small outline DIMM (SODIMM) is available with either 72 pins or 144 pins. Because SODIMMs are smaller than DIMMs, they are often found in notebook computers. SIMM Standard inline memory module (SIMMs) are found in older PCs, and have been largely replaced by DIMMs. They are available in 30-pin and 72-pin packages.

RAM is not the only kind of memory used in a PC. Data and instructions can be stored in read-only memory (ROM) chips. Unlike RAM, ROM is nonvolatile – it is retained even when the power is switched off. For this reason, ROM is used to store the basic input/output system (BIOS) services and configuration information. Two types of ROM chips that you may find on a typical motherboard are  

non-reprogrammable ROM flash ROM

non-reprogrammable ROM Older motherboards contain several non-reprogrammable ROM chips. You can't change the data stored on this kind of chip. If you stored the BIOS on such a chip – a ROM BIOS chip – you'd have to physically replace the chip to change the BIOS. So, the BIOS, which can be thought of as a set of small programs, is permanently stored on the chip. Programs stored in this way are known as firmware – a hybrid between software, which can be easily erased, and hardware. flash ROM The flash ROM chip performs the same function as previous generations of ROM chips – it stores the BIOS, for example. However, you can reprogram the data held on the chip.

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The data on the chip is still nonvolatile, and is permanently stored on a flash ROM chip unless you decide to reprogram it. Chips of this kind make it possible to update the BIOS using software, rather than physically replacing the chip.

3. Connectors, jumpers, and switches As you have seen, there are several external connectors, or ports, which may be built in to the motherboard. These connectors allow devices outside the PC – peripheral devices – to be attached to the PC. Different devices use different connector types. Some of the common connectors are    

DIN DB RJ Audio

DIN DIN (a German acronym for Deutsches Institut für Normung, meaning German Industry Standard) connectors are round and come in two sizes – 5-pin DIN and the smaller 6-pin mini-DIN. The miniDIN connector is also known as a PS/2 connector. DIN sockets are female. Devices that use DIN or mini-DIN sockets include the keyboard and mouse. DB DB connectors are D-shaped, so you can insert the plug into the socket only in one way. These types of connector have between 9 and 37 pins, and the sockets they fit into can be either male or female. DB connectors are typically used for the parallel and serial ports on the computer, and so can accommodate many devices, from printers to a mouse. RJ The RJ (Registered Jack) connector is found on most PCs, where two types are used. The familiar connection for a phone jack is an RJ-11 connector, which you use for modems. The wider RJ-45 connector is used for network connections. Audio The mini-audio connectors are round connections that accept a small single-prong plug. They are used to connect to various kinds of audio device, such as headphones and microphones, and may be color-coded according to the type of device that uses the connection.

Centronics ports are D-shaped, and have contacts – instead of pins – that accept a single tab. Centronics sockets are female, and, unlike other connectors, have wire tabs on each side to lock a plug in place. Centronics sockets are found on some printers, but are no longer commonly found on the backs of PCs. British Naval Connection (BNC) connections are found on some network cards. BNC connections resemble TV connections, but are no longer common on PCs. They are also known as coaxial or coax connectors, because of the cable used with these connectors. To insert the cable into a BNC connector, you push it into the connector firmly and then twist to lock the cable in place.

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Universal serial bus (USB) ports are rectangular, and are used to connect a PC to many different USB devices, including scanners, digital cameras and printers. Features that make USB ports popular include the support of the USB technology for  

hot swapping daisy chaining

hot swapping USB supports hot swapping, which means that you can remove one device from a USB port and insert a new device into the same port without restarting the computer. daisy chaining You daisy chain USB devices by linking them to a USB hub. You can daisy chain up to 127 devices on one USB port, and you can make USB devices act as USB hubs.

FireWire, or IEEE 1394, is a very fast data transfer standard. Because of its high speed, it is suitable for digital video cameras. FireWire ports are rectangular, and accept a 4-wire or a 6-wire cable. However, you may need to install a FireWire adapter card to provide a FireWire port. You can configure some motherboards using components that are located on the board itself. You alter these components physically to specify various settings. For most modern PCs, though, such information is stored on an integrated circuit (IC), such as a flash ROM chip. The following types of components may allow you to physically define configuration settings:  

jumpers dual inline package (DIP) switches

jumpers Jumpers are pins that form a circuit when a small cover called a shunt connects them. The way in which the pins are connected by the shunt determines the configuration settings. Jumpers without a shunt are considered open, or off. A jumper circuit is closed – or on – if there is a shunt connecting the two pins it includes. A parked jumper has a shunt on one pin only to allow you to find the shunt easily if you want to use it later. dual inline package (DIP) switches DIP switches are simple switches that perform the same function as jumpers – specifying specific configuration settings. A DIP switch is On when closed and Off when open. The On or Off positions will usually be indicated on the switch itself. The DIP switches may be labeled – S1 or S2 for example. You should use a screwdriver to flip the actual switches, because they are very small.

4. Devices and their connectors

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Computer systems usually have several peripheral devices, such as a keyboard and mouse, a printer, and an external modem. Each type of device attached to a PC uses a particular connector. These connectors are either built in to the motherboard or hosted on an adapter card, which is placed in an expansion slot on the motherboard. Here are some of the typical peripheral devices and adapter cards that may be present in a PC.     

Network, sound, and video cards Keyboard Printer Mouse and joystick Modem

Network, sound, and video cards Adapter cards – such as the network, sound, and video cards – are situated in expansion slots on the motherboard. They have exterior connectors that allow you to attach various devices to the corresponding card. A network interface card (NIC) allows the PC to connect to a network. You can install a NIC in an expansion slot on the PC. NICs can host many different types of connectors, including BNC and RJ-45 connectors. The latter is the most common type of connector found on NICs. Sound cards turn digital information into sound, and vice versa. A sound card has connections for speakers and a microphone in the form of two mini-audio ports on the back of the PC. Some sound cards also have a 15-pin female DB socket so that you can attach a musical instrument or joystick to them. Video cards use a 3-row, 15-pin, female DB connection to which you attach a monitor. Keyboard All PCs have a keyboard port that is connected directly to the motherboard. Older AT systems use a DIN connector, and the newer ATX systems use the mini-DIN (or PS/2) connector for the keyboard. You can use an AT keyboard with a PS/2 socket by using a DIN-to- mini-DIN adapter. Some new keyboards also have a universal serial bus (USB) connection, to which you can attach a keyboard. Printer Many printers are connected to the PC using the parallel port, which is a 25-pin, female DB connector (DB-25S). On older PCs, parallel ports were connected to the motherboard through an adapter card. However, modern PCs have a built-in parallel port, which is directly connected to the motherboard. Mouse and joystick You connect a mouse using either a connector hosted on an adapter card, or a built-in, standardized port. In older PCs, you used to have to add devices – even a mouse – to a motherboard through unused expansion slots, which were designed for that purpose. IBM created standardized PC ports to allow you to connect devices, such as the mouse, to a PC without opening the case to access the motherboard. The original standardized port was the serial port, which transmits data in a serial fashion, one bit

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at a time. The serial port, which the mouse used to use, is either a 9-pin male DB connection or a 25-pin male DB connection – the IBM super-standard serial port. The 25-pin serial port is no longer common, but there is at least one 9-pin serial port on almost all PCs. Because a mouse is an integral part of the modern PC, dedicated mouse ports in the form of a mini-DIN (or PS/2) connection are now common on PCs. However, some mouses might use the USB port. Some PCs have a 15-pin, female DB connector for a joystick, which is a pointing device used mostly for computer games. In this case, the connector is hosted on the sound card. Modem Modems transform the analog signals from a telephone line into digital data. There are two common types – internal and external. An internal modem is an adapter card, designed for data transmission, which – like all cards – fits into an expansion slot. An external modem plugs into a serial port on the outside of the PC case. Most internal and external modems have two RJ-11 connectors. You use one connector to connect the modem to the telephone jack. The other connector allows you to connect a telephone line to a PC so that you can use the telephone when you are not using the modem.

In order to function, devices must send and receive data from the PC, and this can be carried out in two modes – duplex or half-duplex. The half-duplex mode means that the device can only send or receive data at any one time. Some printers that use the parallel port may communicate in this mode. However, the vast majority of devices use the full-duplex mode, in which data can be sent and received by a device at the same time.

5. Casing types and adapter cards The motherboard and the internal PC components, including power supply, expansion cards, and drives, are enclosed by a computer case. Most cases have lights on the front, which indicate when the PC is on, and switches that you use to turn the PC on and off. Computer cases may be categorized as one of the following types:  

Desktop Tower

Desktop The desktop case is a flat rectangular case, designed to sit on a desktop. The motherboard is located at the bottom of the case, and the power supply is at the back. A desktop case usually has four drive bays, and six expansion slots. A desktop case takes up a lot of space on the desktop, and so is being replaced by smaller, more compact case types. One such type is the slimline, or low profile case, which is a smaller version of the full-sized desktop case. Tower

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The tower case is higher and narrower than a desktop case, and provides space for several drives. The tower version comes in three sizes – mini-tower, midi-tower, and full-size tower. Because they provide a lot of space for drives, full-size towers are often used for servers. A tower case allows you sufficient space to house additional components and to work easily in the case.

Notebook computers usually use a proprietary case, which is small and compact.

Summary The CPU, RAM, power supply, floppy disk drive (FDD), hard disk drive (HDD), and external devices connect to sockets on the motherboard. Other components are soldered directly onto the board. RAM stores the data that the CPU is using at a particular time. Its data is erased when you turn the PC off. RAM is available as different types of memory modules, of which 168-pin dual inline memory modules (DIMMs) are the most common. Small outline DIMMs (SODIMMs) and standard inline memory modules (SIMMs) are also available. Devices outside the PC – peripheral devices – connect to a PC through connectors, or ports. Different devices use different port types such as Deutsches Institut für Normung (DIN), DB, Registered Jack (RJ), Audio, Centronics, British Naval Connection (BNC), universal serial bus (USB), and FireWire (IEEE 1394). Some motherboards use jumpers and dual inline package (DIP) switch settings on the board to store setup information. The keyboard, mouse, and printer attach to motherboard connections. Adapter cards such as the network interface card (NIC), sound card, and video card have exterior connections on the back of the computer case so that you can attach devices such as the network cables, speakers, and monitor. Full-duplex peripheral devices can send and receive data at the same time, whereas halfduplex devices can only send or transmit data at any one time. The motherboard and the internal PC components fit into a computer case, which is the part of the PC that is visible to the user. The three major types of cases are desktop, tower, and notebook.

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Power supplies, storage, and display devices 1. Power supply characteristics A power supply unit provides the electrical power for every component in a PC. It converts AC from the mains to a lower DC voltage. Older power supply units provide 5 V and 12 V DC to the motherboard, whereas newer power supply units provide 3.3 V, as well as 5 V and 12 V. As a general rule, the motors on the disk drives use the 12 V power supply, whereas the electronic components use the 3.3 V and 5 V supplies. In addition to providing power to computer components, a power supply unit runs a fan, or a pair of fans. These reduce the temperature inside the case to prevent sensitive components from failing. Depending on the form factor of the motherboard, a PC uses either an  

Advanced Technology (AT) power supply unit Advanced Technology Extended (ATX) power supply unit

Advanced Technology (AT) power supply unit The AT power supply unit is used on older motherboards. The AT power supply has two bundles of six wires, ending in P8 and P9 connectors that plug into the motherboard at connections labeled P1 and P2 respectively. The voltage levels of the P8 and P9 connectors are different, so it's important that they are connected in the correct way. Advanced Technology Extended (ATX) power supply unit The ATX power supply unit has a single 20-pin connector, which is keyed – it has a raised piece of plastic at one edge which fits into a corresponding notch – so that you can't insert it the wrong way around. This connection includes a signal wire that the motherboard uses to turn off the power supply. This feature is called a soft switch.

The P8 and P9 connectors from the AT power supply are connected into the pair of connectors P1 and P2 respectively on the AT motherboard. In the same way, the 20-pin connection from the ATX supply plugs into the corresponding connector on the ATX board. In addition to connections that provide power, both the AT and ATX power supply units have a standard IEC-320 AC power connection. A cable, plugged into the standard AC power supply from the power company, is inserted into this connection and provides the power for the unit. This particular model includes an IEC-320-2-2 connector, which can supply power to another device, usually a monitor. However, this type of connector is not found on most power supply units.

2. Different types of storage devices

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Two kinds of storage are used in computer systems – primary and secondary. Primary storage is used to temporarily hold data and instructions that the CPU is currently using. This kind of storage is provided by RAM. In contrast, secondary storage is used to permanently store the data and instructions used by the CPU. Secondary storage systems for PCs can be magnetic – as in the case of disks or tape – or optical, like CDs and DVDs. One of the most enduring forms of secondary storage is the floppy disk, accessed by floppy disk drives (FDDs). Older FDDs used 5.25-inch floppy disks, but almost all FDDs now use 3.5-inch floppy disks. Double-density 720 KB and high-density 1.44 MB floppy disks are available. An FDD that accepts 3.5-inch floppy disks attaches to a male connection on the motherboard via a 34-pin ribbon cable. This cable has a red stripe running along one edge to identify how you should connect it to the motherboard. A floppy disk controller can support two FDDs on the same cable. A cable from the power supply unit supplies the power to the FDD. A hard disk drive (HDD) is a high-speed, high-capacity, magnetic, secondary storage device. All PCs have at least one HDD. An HDD usually has several gigabytes of storage capacity. Within an HDD, two or more disks, or platters, are mounted on one spindle, and both sides of each disk store data. The spindle mechanism can rotate the disks very quickly, allowing high data transfer rates. The HDD has a read/write mechanism that transfers data to and from the disks, using the read/write heads. The entire assembly is enclosed in a dust-free compartment. Each side of a disk or platter is divided into tracks and sectors. The tracks can be placed very close together, enabling high storage capacity. The two common standards that HDDs can use to communicate with the rest of the PC are  

Integrated Drive Electronics (IDE) Small Computer System Interface (SCSI)

Integrated Drive Electronics (IDE) IDE hard drives use a 40-pin ribbon cable connection to connect to an IDE controller on the motherboard. Motherboards typically have two IDE controllers, which each provides an interface to either one or two HDDs. So most motherboards can support up to four HDDs. Small Computer System Interface (SCSI) A motherboard may have a built-in SCSI controller to which different SCSI devices, including HDDs, can be connected. Alternatively, you can use an adapter card called a host adapter. There are several SCSI standards, with different cables and connectors. SCSI HDDs tend to be faster but more difficult to install than their IDE counterparts.

A CD is an optical, secondary storage medium. A laser writes data to the disc, encoding it by the length and spacing of blisters it creates on the disc surface. A low-power laser then reads the data by scanning

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the disc surface. The surface doesn't wear because there is no physical contact between the disc and the reader. Most CD drives use the IDE standards, , but some use different standards, such as SCSI, universal serial bus (USB), or IEEE 1394 (FireWire). With early CD-ROM drives, you could only read data from the drive. More recently, the following two types of recordable CD drives have been developed:  

CD-recordable (CD-R) drives CD-rewritable (CD-RW) drives

CD-recordable (CD-R) drives CD-R drives allow you to write to special CD-R discs, but not to erase data on these discs. CD-R drives can also read normal CD-ROM discs and most CD-ROM drives can read recordable CD-R discs. CD-rewritable (CD-RW) drives CD-RW drives can write to, delete, and rewrite new data to CD-RW discs. They can also write to CD-R discs, and read all CD types – CD-ROM, CD-R, and CD-RW.

video disc (DVD) is an optical storage technology based on the same principles that CDs use. However, although they look the same as CDs, DVDs can store much more data – up to 17 GB. Typically, data transfer rates for DVD drives range from 600 KBps to 1.3 MBps. As with CD drives, there are different DVD drives for various DVD formats. With a DVD-ROM drive, you can only read data from the disc. There are a number of different writable DVD standards, including DVD-RAM and DVD-RW. These standards may have different storage capacities. And of course, there is the DVD-Video standard, widely used in DVD players. This standard uses the MPEG-2 compression technique to store movies. Tape drives are magnetic, secondary storage devices that use small tape cartridges, the capacity of which can range from 100 KB to several GBs. The most common use for these drives is to back up hard drive data. However, data is stored on the tape cartridge by sequential access, not random access. So, in order to retrieve any data, you must read through the tape sequentially until you find the relevant section. This is the reason why these drives are used to back up other drives, rather than for general, day-to-day usage. Tape drives use two common types of cartridge – full-sized tape cartridges are 4 by 6 by 0.625 inches, whereas the more popular mini cartridges are 3.25 by 2.5 by 0.375 inches.

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A removable drive is a high-capacity, secondary storage device that you can attach or remove from a PC quickly and easily. An example of a removable drive is the popular Iomega Zip drive. You can use a removable drive to increase the existing storage capacity of a PC, to move large files from one computer to another, and to make backups. And because you can lock a removable drive away when it isn't in use, it also allows you to secure important files. When buying a removable drive, you should consider several parameters including the  

drop height half life

drop height The drop height is the maximum height from which the manufacturer specifies that you can drop a removable drive without causing irreversible damage to it. This is important because you will be transporting the drive. half life Almost all removable drives are based on magnetic storage, and the half life of the drive is the period of time it takes for its magnetic strength to weaken by half – usually between five and seven years. This value is typical of most magnetic media, but optical media, such as CD-ROMs, typically have a half life of approximately 30 years.

Examples of removable drives include the   

Iomega 3.5-inch Zip drive Imation SuperDisk Iomega Jaz drive

Iomega 3.5-inch Zip drive The Iomega 3.5-inch Zip drive stores data on removable disks, each of which has a 100 MB or 250 MB storage capacity. Its drop height is 8 feet. Internal Zip drives have an IDE connection, and the external zip drives use a USB, SCSI, or parallel port. The disks are thicker than floppy disks, which this drive cannot read. Imation SuperDisk The Imation SuperDisk has a capacity of 120 or 240 MB, and the drives are backward compatible with double-density 720 KB and high-density 1.44 MB floppy disks. The drives support data transfer rates 27 times faster than that of an FDD. The external drives of this type usually connect to a parallel or USB port. Internal drives are also available. Iomega Jaz drive The Iomega Jaz drive can store 1 GB or 2 GB of data on each removable disk. The drop height of the drive is 3 feet. Internal and external Jaz drives use a SCSI connection, although a SCSI adapter is available that allows you to connect an external drive to the USB port.

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3. Display devices All PCs need an output display, the most common of which is some kind of cathode-ray tube (CRT) display monitor – frequently a video graphics array (VGA) color monitor. The monitor's signal cable connects to a 15-pin D-type connector on the system case of a PC. All CRT monitors are based on the same principle, in which a cathode tube at the back of the monitor generates a beam of electrons that strike a special phosphor coating on the back of the monitor screen. When this occurs, the phosphor lights up for a brief period. The length of time it takes for this luminescence to fade is known as persistence. To create a display on the screen, the electron beam sweeps the entire screen area. For example, the beam might begin in the top left-hand corner of the screen. It then sweeps horizontally across the screen, from left to right, leaving a line known as a raster line. The beam is then blanked, and sweeps back horizontally to the next position, one line below the starting position on the left-hand side. This operation is known as a horizontal retrace. By creating a series of raster lines, each followed by a horizontal retrace, an image can be built up until the bottom of the screen is reached. The beam then moves up to the starting position – a move known as the vertical retrace. With the beam in the starting position, the operation can be repeated. This whole process happens so quickly that the human eye perceives a stable image. In fact, the refresh rate is a measure of how many complete vertical retraces occur in one second, measured in Hertz (Hz). Many monitors have a refresh rate of 60 Hz, which means 60 complete vertical retraces occur every single second. Modern monitors have even higher refresh rates. Color monitors use three different phosphors – colored red, green, and blue – on the coating behind the screen. The colors are grouped next to each other and combined into picture elements – or pixels – on screen. For each of the three colors, there is a separate electron gun. Each gun uses different voltage levels to create varying intensities of a specific color. In combination, different intensities of the three colors supply all the colors that a full-color monitor display uses. All three guns in a color monitor move across the screen at the same time. A metal grid called a shadow mask, positioned between the electron gun and the screen, ensures that each gun strikes the correct phosphor. A pixel is the smallest area on the screen that can be turned on or off, or varied in intensity, by the electron guns. The resolution of a monitor is a measure of the quality of the image that a

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monitor can display. It is expressed in terms of the number of horizontal pixels multiplied by the number of vertical pixels. For example, a monitor screen with a resolution of 800 by 600 has 800 pixels in the horizontal direction and 600 pixels in the vertical direction. The more pixels on the screen, the greater the resolution, and the greater the image quality. In addition to a pixel measurement, resolution can be expressed in terms of a monitor's dot pitch, which is a measure of how far apart the phosphor dots for a similar color (the red phosphors, for example) are from each other. A 800 by 600 pixel display on a 14-inch monitor may have a smaller dot pitch, and therefore produces a sharper and more defined image than the same 800 by 600 resolution display on a 21-inch monitor, with a lower dot pitch. Portable systems, such as notebook computers, use a liquid crystal display (LCD) instead of a CRT monitor. An LCD is based on a liquid crystal, which can be made opaque or transparent depending on the presence of an applied electric field. LCD displays are flatter, lighter, and more compact. They consume less power, and so can run off batteries. They also last longer than CRT monitors. Most LCDs in notebooks are lit from behind the LCD panel – an arrangement known as backlighting. The panel itself is made up of several components, including the polarizers, the row and column electrodes, the color layer, and the liquid crystal layer itself. The intersection of the row and column electrodes forms a single pixel, and the image is produced on the screen by manipulating these electrodes to affect the transparency of the liquid crystal layer.

Summary A power supply unit converts AC from a commercial power supply to a lower DC voltage to power the PC components. A PC's power supply provides power for the motherboard's electronic components and the disk drive motors. It may also power one or more fans so that internal components don't overheat. You can't use older Advanced Technology (AT) style and newer Advanced Technology Extended (ATX) power supplies interchangeably. There are several types of secondary storage. Devices such as floppy disks, hard disks, tape drives, and removable drives are magnetic secondary storage media. CDs and DVDs are optical secondary storage media. These devices have different storage capacities and data transfer rates. Most PCs use a cathode-ray tube (CRT) display monitor. An electron gun emits electrons onto the monitor's phosphor coating, and sweeps across the screen in

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raster lines. Red, green, and blue phosphors create the colors on a color display. Resolution is the quality of the image, expressed in number of pixels. Portable computers use liquid crystal displays (LCDs). The panel for an LCD consists of several layers, which work together to produce an image on screen.

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System boards and power supply units 1. Replacing system boards There are two possible reasons for removing a motherboard. Either the motherboard has failed and you need to replace it, or the computer user wants to upgrade the system by replacing the motherboard with one that has better features. There are five steps you should follow when removing a motherboard. The first step is to remove the I/O connections. To do this, you unplug the power cables, disconnect the mouse and keyboard, disconnect the monitor signal cable from the PC, disconnect the printer connector, and disconnect the monitor power cable from the power supply unit. The second step in removing a motherboard is to remove the outer cover from the unit. There are two types of system cases:  

Desktop Tower

Desktop To remove a desktop case, you first unplug the AC power cord from the unit, and remove the retaining screws that secure the case to the back panel. There are two different desktop styles. Depending on the style, you either slide the cover off forwards, together with the unit's front panel, or you lift the cover off from the back. Tower To remove a tower-type case, such as a full-sized tower, a midi tower, or a mini tower, you first unplug the AC power cord ( if you haven't already done this. Next, you remove the screws from the back panel. Then you either slide the whole case off backwards, or you remove the front panel and slide the side panel off towards the front.

The third step in removing a motherboard is to remove the adapter cards for any optional devices that are installed. To do this, you remove connectors from the card, remembering where to replace them. Then you remove the screws that hold the card in place, and take the adapter card out of the expansion slot. The fourth step in removing a motherboard is to remove the cables from the motherboard. To do this, you disconnect the floppy drive signal cable and the hard drive signal cable from their connections on the motherboard. You unplug the connections for the lights and switches on the front panel from their connectors on the motherboard. Then you disconnect the power supply connections. Once you have removed all connections, the final step in removing a motherboard is to record the jumper settings, using the board's user manual to help you determine what each setting means. This allows you to use the correct

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settings when you reinstall a motherboard. If the motherboard has plastic standoffs, you then free them from the slots in the case's floor, and slide the board out of the system unit. You follow the same steps in reverse to install a motherboard:     

Replace the board Replace the cables Replace the adapter cards Replace the unit's cover Replace the I/O connections

Note You should put adapter cards back into the same slots that you removed them from. You can replace the following components on the motherboard:   

Microprocessor Memory Adapter cards

Microprocessor Microprocessors are mounted in sockets, so you can replace them easily. A zero insertion force (ZIF) socket allows you simply to put the microprocessor in the socket, and clamp the pins with a lever arm. A notch and dot on the corner of the microprocessor – usually at the free end of the locking lever – mark the location of pin 1. You should check the heat dissipation and speed rating of the processor you install, as these affect the power supply and fan required. Memory Motherboards usually have rows of 72-pin single inline memory module (SIMM) and 168-pin dual inline memory module (DIMM) sockets. You slide a DIMM into a socket, and lock it with tabs at each end. SIMM slots have a tab at one end, so you can insert a SIMM in one way only. You insert it at a 45-degree angle, and move it to the vertical until it snaps in place, and is locked. The PnP process detects and configures RAM automatically. Adapter cards First, you check the adapter card's installation information. Then you remove the expansion slot cover from the back of the system unit, and push the card firmly into the correct slot. You attach it to the unit with a screw, and then attach its external connections. After switching on the PC, you install device drivers if needed. If you attach a PnP device to the card, the system will configure it automatically, so you don't need to install a driver.

2. Replacing power supplies and fans To remove a power supply unit so that you can replace it, you must remove its connections to the power source and to other devices. Removing a power-supply unit involves the following steps:  

disconnecting exterior power connections disconnecting interior power connections

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

removing the power-supply unit

disconnecting exterior power connections To disconnect the exterior power connection, you unplug the power cable from the outlet. In an Advanced Technology (AT) system, you unplug the monitor's power cable from the power supply as well. disconnecting interior power connections Disconnecting interior power connections involves disconnecting the power supply from the motherboard, the floppy disk drive, the hard disk drive, the CD-ROM drive, and any other devices that are connected to the power supply. You should also disconnect the front panel switch, if there is one. removing the power-supply unit To remove the power supply unit, you remove all the screws that hold it in place at the back of the case. Sometimes you also need to remove screws from the front of the unit. You then lift the power supply unit out of the system.

When purchasing a replacement power supply, you need to consider its wattage – which is a measure of the total power that the unit can deliver to the system. Systems with more peripheral devices and disk drives require power supplies with higher wattage ratings. The power supply must also be suitable for the motherboard's form factor. You can't install an AT power supply on an Advanced Technology Extended (ATX) board or vice versa. When installing an AT power supply, you should remember not to reverse the P8 and P9 connectors because their voltage levels are different. When connecting the P8 and P9 connectors to the motherboard, you must keep the black ground wires next to each other in the center. An ATX power supply has a single P1 connector instead of the P8 and P9 connectors found on AT power supplies. The P1 connector requires its own special socket on the motherboard. The P1 connector is notched so that you can insert it in one way only. Before you install a processor on a Slot 1 motherboard, you need to install a fan, along with a heat sink, onto the microprocessor. The steps you follow to install a fan are     

unfolding the arms on the motherboard fitting the fan to the processor cartridge fitting the fan and processor cartridge to the motherboard locking the processor cartridge in place connecting the power

unfolding the arms on the motherboard

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You unfold the arms of the universal retention mechanism (URM) on the motherboard, until they lock into place. fitting the fan to the processor cartridge You examine the fan and processor to see how the fan brace aligns with the holes in the side of the processor cartridge. Then, on a hard surface, you fit the fan tightly to the side of the processor cartridge, and push the fan clamp down to secure it to the cartridge. fitting the fan and processor cartridge to the motherboard You insert the fan and the processor cartridge into the universal retention mechanism (URM) arms so that they fit tightly into the slot, and you snap the arms into position. locking the processor cartridge in place You pull the processor cartridge locks outward until they lock into the holes on the universal retention mechanism (URM) arms, locking the processor cartridge into place. connecting the power To complete the process of installing a fan, you connect the fan's power cable to the motherboard's power connection.

Summary You might need to replace a motherboard if it has failed or if you want to upgrade a system. To do this, you first remove the I/O connections, remove the outer cover, remove the cables, and record the jumper settings. You then lift the motherboard out of the system. Components on the motherboard that you can replace include the processor, memory, and adapter cards. To replace a power supply, you first remove its connections to the power source and to other devices. The new power supply must be compatible with the form factor of the motherboard and with the system's wattage requirements. To install a fan, you unfold the universal retention mechanism (URM) arms on the motherboard, fit the fan to the processor cartridge, and install the processor on the motherboard. Then you lock the processor in place and connect the power.

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Installing storage devices 1. Installing and removing storage devices The distinction between external storage devices and internal storage devices is a key consideration when planning how the device is to be installed. Internal storage devices are typically mounted in one of the system unit's drive bays, whereas external devices usually connect to adapter cards in the expansion slots on the motherboard and almost always require separate power supplies. Common internal devices that you might need to install are floppy disk drives (FDDs), hard disk drives (HDDs), and CD-ROM drives.   

Floppy disk drive (FDD) Hard disk drive (HDD) CD-ROM drive

Floppy disk drive (FDD) Most internal storage devices – such as FDDs, HDDs, and CD ROM drives – have similar physical characteristics, which implies that the procedures for installing such devices are similar. The process of removing and re-installing an FDD includes the following steps, which could also be applied to other internal devices: turn off the power and insert the drive connect the signal cable to the motherboard connect the signal cable to the drive connect the power cable to the drive Before installing any internal drive, including an FDD, you should disconnect the PCs power cords, slide the drive into an open drive bay, and secure the device to the drive cage. In some instances, the drive bay may be larger than the drive – for example if you are inserting a 3.5-inch FDD into a bay designed for a 5.25-inch drive. In these cases, you should fit a universal mounting kit to the drive. These kits effectively extend the drive so that if fits correctly into the drive bay. After inserting the drive into the bay, you have to correctly connect a signal cables to it and to the motherboard or to an adapter card – in the case of some SCSI drives, for example. This will require you to remove the cover from the case. A PC compatible FDD uses a 34-pin ribbon cable. This ribbon cable is inserted into the FDD controller found on the motherboard. The cable has a red stripe running down one side, which you should align with pin 1 of the FDD controller, as identified on the board. Once the signal cable is attached to the motherboard or adapter card, you must attach it to the drive. For FDDs, you must attach the 34-pin ribbon cable into the correct connection in the back of the drive. Once again, you must align the red side of the cable so that it is aligned with pin 1, as identified on the drive connector. The FDD controller on the motherboard can support two floppy drives. If you want to install the

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new drive as drive A, you connect it to the end of the cable. To install it as drive B, you connect it to the middle of the cable. A twist in the wires between these two connections differentiates the two drives. When the signal cable is connected properly, the power cable must then be attached to the drive. Power is supplied to the FDD using one of the connectors from the power supply. Once this has been connected properly, you are in a position to boot up the PC. You may need to use the CMOS Setup utility to configure the drive and you can test that the drive is working by copying or formatting a floppy disk. When you're sure that the drive is working correctly, you replace the computer cover. Hard disk drive (HDD) The physical installation of an HDD is similar to that of an FDD – the drive is placed in an empty drive pay, secured, and the proper signal and power cables attached. However, you may have to change some settings on the drive itself, such as the master/slave/single parameters for IDE drives, or the ID for SCSI drives. These settings would be configured before the drive was inserted into the bay. Also, if you are replacing an HDD, you should back up the data on the original drive. When installing an IDE drive, remember that the motherboard IDE controllers – a primary and a secondary controller. Each controller can support a master and a slave hard drive. Before you install an HDD, you need to decide on which IDE channel you are going to install the hard disk. If you plan to use only one HDD, it should be the only drive on the primary channel. After the HDD has been physically installed, you may have to manually set up the CMOS configuration for the drive, or, as in most cases, allow the system to auto detect the drive. Then you must partition and format the HDD. Partitioning is the process of electronically dividing the physical drive into one or more separate areas, called partitions, whereas formatting configures these partitions so that they can be used by a particular operating system (OS). There are two different kinds of partitions primary and extended. The primary partition is where the OS is installed. With Microsoft FAT based systems, the primary partition must be the C: drive, and it must be set to the active partition – that is the partition from which the system will boot. Even if there is only one primary partition, you must set this to be the active partition. However, an HDD can have up to four primary partitions, and you can use these partitions to store multiple OSs. The system will boot up to the OS stored on whichever primary partition is designated as the active partition. An extended partition does not contain the OS, so the system cannot boot from it. An HDD can only contain one extended partition. However, this kind of partition may be subdivided into a number of logical drives, each assigned a different drive letter. The size of the logical drives can vary, and if you decide to use an extended partition, you have to create at least one logical drive on it. The partitioning process is carried out using software tools, such as the Disk Administrator (Windows NT 4.0) or Disk Management (Windows 2000) utilities. Older Windows versions, and DOS, use the FDISK program. CD-ROM drive All drives which use a CD, including CD-ROM drives and CD-RW drives commonly connect to the motherboard via the same IDE interface typically used for the HDD. However, some CD drives use a small computer system interface (SCSI) controller. The steps for installing a CD drive – which uses an IDE controller – are similar to those for

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installing an FDD or HDD. You insert the drive connect the cables turn on the PC test the drive To insert a new CD drive, you turn off the PC, open the case, and slide the drive into an empty bay. You might need to use a universal mounting kit if the drive is too small for the bay. As with HDDs, you may need to configure IDE or SCSI settings on the drive itself, before it is inserted in the bay. You connect the power cable and the 40-pin ribbon cable to the drive. As with HDDs and FDDs, the ribbon cable must be aligned correctly, so that pin 1 in the drive is correctly connected to pin 1 on the IDE controller. You may also have to attach an audio cable to a sound card, if there is one. For some drives, you need to attach a ground connection. You should check the drive's manual to determine if this is necessary. You turn on the PC and press the eject button on the front of the drive. If the eject function works, you know that the drive is receiving power. If the drive is Plug and Play (PnP) compatible, Windows launches the Found New Hardware Wizard. This wizard guides you through the process of installing Windows drivers for the CD drive. If the CD drive is not PnP compatible, you use the Add New Hardware icon in the Control Panel to configure it. Windows assigns the next free drive letter to the CD drive. To test the CD drive, you access it using the appropriate drive letter in Windows Explorer. If you are recovering from a failed HDD, you'll need to access the CD drive, as Windows is normally loaded from such a drive. However, if the hard drive has failed, you will not have access to the drivers for the CD drive. For this reason, versions of Windows later than Windows 98 include these drivers on their rescue disks, but in Windows 95, rescue disks do not. To install new CD-ROM device drivers on a Windows 95 rescue disk, you need to copy the following files to the root directory of the disk: the device driver that the CD-ROM manufacturer provides a real-mode operating system (OS) interface called mscdex.exe, which you find in the C:\Windows\Command folder In addition to copying the files to the root directory of a rescue disk, you need to alter the config.sys and autoexec.bat files to allow a Windows 95 system to access a CD drive when booting from the rescue disk. To access the CD drive from the rescue disk, you add the following syntax to the autoexec.bat file: mscdex.exe /d: drive_name [/l:drive_letter][/m:number_of_buffer _zones] The code mscdex.exe identifies the mscdex.exe file, the interface to the driver. The code /d:drive_name identifies the drive to the mscdex.exe file. So for example, if you entered the code d:/my_drive, the drive, to mscdex.exe, would be named my_drive.

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The mscdex.exe file can assign a drive letter to the drive using the /l: option. To specify E: as the drive letter, for example, you enter the code /l:e in the full code line. The /m: option allows you to specify the number of memory buffers. To specify the use of 10 buffers, for example, you enter /m:10 in the full code line. When mscdex.exe is executed, it will look in config.sys, using the drive name specified in sutoexec.bat as a tag to locate the device driver. So you have to associate the drive name you specified in mscdex.exe with the correct driver, using the following syntax: device = drive_letter:\device_driver /drive_letter:drive_name When mscdex.exe is executed, it will look in config.sys, using the drive name specified in sutoexec.bat as a tag to locate the device driver. So you have to associate the drive name you specified in mscdex.exe with the correct driver, using the following syntax: device = drive_letter:\device_driver /drive_letter:drive_name The first part of this syntax identifies the location and name of the device driver for the CD drive. The second part of the syntax identifies the drive name, as specified in mscdex.exe. So to allow an OS interface called mscdex.exe to use a device driver called cdtech.sys, identified with the name my_cd_drive, to access a CD drive, you place the following code in the autoexec.bat and config.sys files respectively: mscdex.exe /d:my_cd_drive /l:e /m:10 device = a:\cdtech.sys /d:my_cd_drive

2. DVDs, tape drives, and removable storage Other types of internal and external storage devices – apart from CD drives FDDs, and HDDs –are DVDs, tape drives, and removable storage devices.   

DVDs Tape drives Removable storage devices

DVDs DVD drives are based on an optical storage technology, and its great advantage is that individual DVDs can hold considerably more data than a CD. For this reason, DVD drives are often used in multimedia applications, such as digital movie editing. The data from a DVD, as read by the DVD drive, is split into sound data and video data, which need to be decoded in some way. Typically, this can be accomplished using an adapter card, a DVD decoder card, which is sold with the drive. This may not always be the case, so, when installing a DVD drive, it is essential that you follow the manufacturer's directions. As with HDDs, internal DVD drives can use the IDE controllers on the motherboard or a SCSI host adapter. The typical set of components required for a DVD drive which uses the IDE controller is a decoder card to decode the sound and video data from the DVD drive

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the DVD drive – which has a similar form factor to a CD drive – is installed internally in a bay on the system's case a standard 40-pin IDE cable, that connects the DVD drive to the IDE controller on the motherboard DVD driver files, which are usually supplied on a floppy disk a video loopback cable that connects the video card to the DVD decoder, so that the decoder can decode the data from the video card before sending it to the monitor Audio decoder cables that connect the DVD drive to the decoder card, and the decoder card to a sound card to allow decoding of sound data and the sending of this data to the sound card. In other cases, you may be able to connect the drive directly to the sound card. To install a DVD drive, you perform the following steps: prepare the drive and case insert the drive connect the IDE, audio, and power cables insert the decoder card connect the video loopback cable As with other internal storage devices, the installation of a DVD drive should begin by turning off the PC and removing the cover of the case. For DVD drives which use the IDE controller, such as this one, the drive is by default set to slave, so you should check that this is the setting on the actual drive before you insert it into the bay. To actually insert the DVD drive, you slide it into the front of the free bay, and secure it with screws, placed on either side of the drive. You connect the power and IDE cables to a DVD drive in exactly the same way as you would for an HDD, ensuring that the red stripe along the edge of the ribbon cable is aligned with pin 1 on the DVD drive and on the IDE controller. With most DVD drives, you will also have to use the DVD drive audio cable (supplied with the drive) to the analog audio connection on the back of the DVD drive. If you can't access the drive once you've inserted it, you should connect the cable to the drive before you insert it in the bay. Once you've connected the cables to the drive, you insert the DVD hardware decoder card into an expansion slot – a PCI slot for example – and secure it with a screw. Having installed the decoder card, you can now use the video loopback cable to connect the video card and this card. Once you've installed a DVD drive, you turn on the PC, and Windows may recognize the drive as a CD-ROM drive. To use it as DVD drive, you need to install the device drivers for the DVD drive from floppy disk. Tape drives You can use a tape drive as an inexpensive way of backing up the contents of a hard drive. Tape drives may be internal or external devices. A tape drive can use the following interfaces: a parallel port a SCSI bus

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an adapter card the floppy drive interface an IDE ATAPI interface

The most common type of tape drive interface is the IDE connection. The procedure for installing an IDE tape drive is the same as for any IDE device. You need to set the jumpers to specify the drive configuration as master, slave, or cable-select, based on the manufacturer's instructions. Then you install the tape drive, and connect the power and 40-pin IDE cables. You should not put the tape drive on the same IDE channel as the hard drive, because this might slow down the hard drive's performance. An example of an appropriate configuration is to install the hard drive as the only device on the primary IDE channel, and to install a CD-ROM drive as a master and a tape drive as a slave on the secondary channel. Removable storage devices You can use a removable storage drive to increase the storage capacity of a system, and to move large files between computers. Typical removable storage drives include the Iomega Zip drive and Jaz drives. Although these drives are external drives, removable storage drives can also be internal. To install a removable storage device, you identify the connector as parallel, USB, or SCSI connect the drive to the appropriate port connect the power turn on the PC and install the software A parallel drive has two 25-pin connections – one for the cable joining the drive to the parallel port of the PC, and another to which you can connect the printer cable. A USB storage device might have a second USB connection for another USB device. A SCSI drive has a 25-pin, 50-pin, or 68-pin connection for the cable to the PC, and a connector for another SCSI device on the external SCSI bus. You need to turn off the PC to connect the drive to a parallel or SCSI port. For a SCSI interface, you then connect the SCSI cable to the drive and to the SCSI port on the host adapter. You then set the drive's SCSI ID. You may also need to set the host adapter to recognize an external device. For a USB device, you simply connect the USB cable to the USB port.You plug the drive's AC power cable into the wall socket. Lastly, you turn on the PC, and install the software from the disk accompanying the removable drive.

Summary Storage devices may be classified as either internal or external. You mount internal devices in one of the system unit's drive bays and typically connect

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external devices to adapter cards in the expansion slots. Common internal devices that you might need to install are floppy disk drives (FDDs), hard disk drives (HDDs), and CD-ROM drives. To install any internal storage device, you check that the PC is working correctly, turn off the computer and remove the cover, connect the data and power cables, and then turn on the PC. Other examples of storage devices include DVD drives, tape drives, and removable storage drives. The installation process for a DVD drive which uses the IDE controller is similar to that for any IDE device, except you need to connect the cables for audio and video, and you might need to install a hardware decoder in an expansion slot. You can install a tape drive on the parallel port, a small computer system interface (SCSI) bus, an adapter card, the floppy drive interface, or – most commonly – the Integrated Drive Electronics (IDE) interface. Removable drives commonly use a universal serial bus (USB), parallel, or small computer system interface (SCSI) connection.

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Adding adapters and input devices 1. Adding and removing input devices Two of the most common input devices for PCs are the mouse and the keyboard. These usually plug into dedicated ports on the motherboard. Most keyboards and mouse devices today use the same connector - a 6-pin mini-DIN, or PS/2, connector, that plugs into the corresponding 6-pin female port at the back of the computer.

Note Another type of connector associated with keyboards is the Shielded Data Link (SDL) connector. One end of this connector – unlike the miniDIN connector – fits into the keyboard. The other end uses an appropriate DIN connector to plug into the PC. Types of DIN connectors are the  

5-pin DIN 6-pin mini-DIN

5-pin DIN The 5-pin DIN plug fits into a half-inch, round, female connector on the back of a system's case. The five pins are for the keyboard clock, serial data, reset, ground, and the power supply. Older Advanced Technology (AT) systems use this kind of keyboard connector. 6-pin mini-DIN The 6-pin mini-DIN plug fits into a quarter-inch, round, female connector on the back of the system's case. Each pin has a specific function. Advanced Technology Extended (ATX) boards usually have a built-in mini-DIN connector, which is the most widely used kind of keyboard connector.

Some devices allow hot swapping – you can plug or unplug them while the system is powered up. However, you should not attach a keyboard to a system with the power on, because electrostatic discharge (ESD) might damage the keyboard and the motherboard. On an Advanced Technology Extended (ATX) board, the mouse plugs into a 6pin PS/2 connection – the same type of connection as the keyboard. An informal convention is that the keyboard connection is colored purple and the mouse connection is green. On an AT board, the mouse is connected to the 9-pin serial port. On an ATX system under the Windows operating system, you simply plug in the mouse and let the OS detect it when you turn the system on. If the OS fails to detect the mouse, however, you should check that the port's hardware is enabled and that the mouse's driver is installed. Installing a serial mouse is a little more complicated than installing a PS/2 mouse, and involves the following steps:

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  

configuring the port attaching the mouse configuring the mouse software

configuring the port To configure the port for a serial mouse, you first remove the unit cover, and locate the serial port adapter on the AT or ATX motherboard. If there is a ribbon cable between the adapter and the connector, you should check that pin number 1 of the cable is lined up with pin number 1 of the adapter. You start the computer, enter the CMOS Setup utility, and check for port enabling settings – the IRQs and the I/O addresses – in the Extended CMOS screens. Then you turn the system off again. attaching the mouse To attach a serial mouse, you plug it into the 9-pin serial connector on the back of the system unit. configuring the mouse software To configure the software for a serial mouse, you should check the mouse settings in the Control Panel. If the correct mouse driver isn't installed, you need to install it.

A touch screen is an input device that uses a grid to sense touch in the same way that a mouse senses clicks. In response to touch, it sends signals to the computer via a universal serial bus (USB) or serial port. A touch screen can be embedded in a monitor or a liquid crystal display (LCD) panel. You can also install a touch screen as an add-on device to a monitor, in which case it will have its own AC adapter. You should follow the manufacturer's instructions when installing a touch screen as an add-on device. In general, you attach the touch screen to a monitor or liquid crystal display (LCD), connect the screen to a USB or serial port, connect it to a power supply, and then install the correct device drivers and management software. Then you reboot, and use the management software to calibrate the resolution of the touch screen in accordance with the monitor's resolution.

Note Whenever you change the monitor's resolution, you should recalibrate the touch screen.

2. Adding and removing adapters Specialized peripheral devices may require the addition of an adapter card into a free expansion slot on the motherboard. You install an adapter card in the following steps:    

Read the installation information Install the adapter card Attach the external connections Install the device drivers

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Read the installation information You should first check the installation information in case you need to make any manual configuration settings. For example, if the device you plan to connect to the card doesn't support Plug and Play (PnP), you may need to set jumpers on the card to configure it. Install the adapter card You remove the expansion slot cover from the unit's back panel, and push the adapter card into the expansion slot. You attach the card to the back panel with a screw. Attach the external connections You attach external connections to any external devices – for example, you attach the network cable for a network card. For a sound card, you attach the connections to any devices – a microphone, for example – that you want to use with the card. Install the device drivers As the final step in installing an adapter card, you install the device drivers that the card requires. Remember that if the device is PnP compatible, the operating system (OS) can detect and configure it automatically. The operating system then loads additional drivers, so you may not need to install them yourself.

To remove an adapter card, you first remove all cables, remembering where they connect to the card. Then you remove the retaining screws that secure the adapter card to the back panel, and lift the card out of the expansion slot.

Summary The mouse and the keyboard are the most common input devices. The different kinds of keyboard connectors are the 5-pin DIN and 6-pin mini-DIN connectors. The mouse uses either a mini-DIN connector or a serial port. Another kind of input device is a touch screen. To install a touch screen, you should follow the manufacturer's instructions. Specialized input devices may need adapter cards. To install an adapter card, you first read the installation instructions, place the adapter card in a free expansion slot, attach any external connections, and install the device drivers, if necessary. To remove an adapter card, you first remove all cables and the retaining screws that secure the card to the back panel. You then lift the card out of its expansion slot.

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Input devices and power sources for portable systems 1. Adding and removing input devices A notebook computer – or laptop – is a small, lightweight system, designed to be fully portable. Notebooks can offer all the functionality of a desktop computer, but are generally more expensive. Notebook computers most commonly use a flat-panel liquid crystal display (LCD) screen, located inside the flip-top display casing. If the LCD panel fails, you probably have to replace the entire display panel with an identical component. Many notebook computers can be connected to external I/O devices, such as full-size keyboards and standard cathode-ray tube (CRT) monitors. Generally, when such a device is plugged in, the built-in equivalent is disabled. For example, the built-in keyboard may not be used if an external full-size keyboard is connected. The typical modern notebook computer offers a standard range of I/O ports which can, for example, accommodate external I/O devices. These ports are situated either at the back or at the side of the unit and can include       

Universal serial bus (USB) port Serial port Parallel port Video Graphics Adapter/Super Video Graphics Adapter (VGA/SVGA) port PS/2 or mini-DIN port Infrared data port DC-in connector

Universal serial bus (USB) port The USB port allows you to connect a wide range of peripheral devices – such as a CD-rewritable (CD-RW) drive – to a notebook computer. Serial port Most notebook computers provide a two-row, DB-9 serial port. Parallel port Notebooks typically use the standard DB 25 parallel port to communicate with external printers. Video Graphics Adapter/Super Video Graphics Adapter (VGA/SVGA) port The high-density 15-pin video port allows you to connect a notebook to an external monitor. Depending on the software installed on the notebook, it may be possible to maintain the notebook's display when you connect it to an external monitor. PS/2 or mini-DIN port The PS/2 or mini-DIN port uses a 6-pin connector. You use this to connect an external keyboard to a notebook computer or an external PS/2 style mouse.

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Infrared data port The infrared data port allows standard, wireless connectivity between a notebook and compatible peripheral devices. DC-in connector The DC-in connector enables you to connect a notebook computer to an external power supply.

As notebooks become more powerful, many people want to use them exclusively rather than relying on another desktop PC when in the office. When they are at their desk, however, they may want to use external devices, such as CRT monitors, full-size keyboards, or CD-RW drives. Although the I/O ports found on most notebooks can accommodate many peripheral devices, it is clearly inconvenient to plug and unplug each device every time you leave or return to your desk. There are two common accessories that provide quick and convenient methods of connecting a notebook to peripheral devices, effectively turning it into a desktop computer. These are  

docking station port replicator

docking station A docking station is a proprietary hardware frame for a notebook computer that provides connections for peripheral devices – such as a printer, full-sized keyboard, larger monitor, and PCport connectors. In addition, a docking station may allow a notebook computer to connect to a zip drive or a floppy disk drive to provide it with extra storage capacity. port replicator A port replicator is similar to a docking station in that it allows you to connect a notebook computer to extra ports and a power supply via a single cable. However, it typically does not provide the additional disk drive and adapter card expansion slots found on a docking station.

A notebook computer is connected to the docking station using a proprietary docking port. As you've learned, you can connect an external keyboard to a notebook computer. You usually do this using a 6-pin mini-DIN (PS/2)-type connector. Plugging in the external keyboard normally overrides the notebook computer's internal keyboard. The same connection can also be used for an external PS/2-style mouse. Onscreen is a notebook computer connecting to an external keyboard by a 6-pin mini-DIN (PS/2)-type connector.

2. Adding and removing power sources All notebooks require a power source, which is either the rechargeable battery or an external power supply. Two types of external power supply that may be used with notebook computers are

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 

AC adapters DC-to-DC converters

AC adapters AC adapters convert commercial AC voltage into DC voltage, which a notebook computer can use for normal operation and to recharge its batteries. DC-to-DC converters DC-to-DC converters, or DC adapters, allow a notebook to use a DC power source, such as an automobile power point.

If an external power source is not available, a notebook can use a battery, which is rechargeable and detachable. These batteries recharge automatically when a notebook computer is using an external power supply. Although the integrated circuits (ICs) in a notebook are designed to extend the battery life, there will be situations – a long business trip, for example – in which you will need to replace the battery, rather than recharge it. Most notebooks have some kind of low battery warning, which indicates when you should replace the depleted battery with a charged one. The procedure for this follows the same general steps, but you should consult the manufacturer's guidelines for specific procedures. To replace a battery, you generally perform the following steps:     

Step 1 Step 2 Step 3 Step 4 Step 5

Step 1 Switch the notebook computer off and remove any external cords and cables, if present. Step 2 Turn the notebook upside down, so that its back is facing up. Step 3 All notebooks have a slide or switch that enables you to open the battery compartment. Locate this to open the compartment. Step 4 Lift the battery out of the notebook. Step 5 Clean the edge connectors of the replacement battery with a clean cloth and place it into the notebook.

Previous generations of notebooks used Nickel-Cadmium (Ni-Cd) batteries, but most notebook batteries today use Nickel Metal Hydride (Ni-MH) or Lithium Ion (Li-Ion) batteries. Ni-MH and Li-Ion batteries offer longer battery lives and a greater total lifespan than their Ni-Cd counterparts.

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Summary A notebook, or laptop, computer offers the same functionality as a desktop computer, but is small and portable. Most notebooks have a number of I/O ports, which can accommodate peripheral devices. These devices can also be connected to the notebook using a docking station or a port replicator. AC adapters and DC-to-DC controllers make it possible for the notebook computer to connect to external power supplies. To replace a notebook computer's battery, you should refer to the manufacturer's instructions.

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Storage devices and adapters for portable systems 1. Installing and upgrading memory A notebook computer uses smaller memory modules than a desktop computer. For example, some notebooks use the 72-pin small outline DIMMs or SODIMMs. A 144-pin version is also available. Smaller notebooks may use the MicroDIMM, which is smaller than a SO-DIMM. Other notebooks can accommodate a 160-pin small outline RIMM, or SO-RIMM. And before notebook computers began using memory modules, credit card memory that inserted into a memory slot was available. You can increase the amount of RAM in a notebook by adding or replacing the memory module. The general procedure for adding a memory module is to   

turn off the computer, disconnect all external cables, and remove the battery remove the memory module panel cover, insert the memory module, and replace the cover reconnect the computer

The general memory upgrade procedure for most notebooks can be divided into the following discrete steps, although you should consult the notebook user manual for specific directions:     

Step 1 Step 2 Step 3 Step 4 Step 5

Step 1 First, you turn off the computer. In most cases, you must power down completely to ensure that you do not damage the notebook or the memory module. Remember that many notebooks have different power-off modes – typically known as Standby or Hibernation modes – and you should not attempt to upgrade the memory when the notebook is in these modes. After turning the notebook off, you should remove any cables connected to it. Step 2 The second step is to turn the notebook upside down and remove the battery pack. Step 3 The third step is to remove the screws securing the memory module panel cover and lift it off. Step 4 The fourth step is to insert the memory module into a free connector, pressing it carefully and firmly to ensure a solid connection. Step 5 To finish upgrading the memory, you reseat the cover, secure the screws, replace the battery, and add any cables removed in the first step.

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Once you've replaced a memory module, you switch the notebook computer back on and it should automatically recognize the new memory module you've installed. As you would expect, the procedure for removing a memory module is almost the same as that for replacing one. The first three steps are the same – once you've turned off the computer, you disconnect it; remove the battery, and the memory module panel cover. In Step 4, however, you remove the old memory module by loosening the retaining clips on either side of the module to release it. You can then pull it out of the slot. You should take care not to touch the connectors on the memory module or in the memory slot, because fragments of debris that accumulate in this way can cause memory access problems. You should then reseat the cover, secure the screws, replace the battery, and add any cables as before.

2. Installing storage devices A notebook computer does not have the same expansion capability as the desktop computer. Notebook users therefore have to decide on the storage device most appropriate for their purposes. The size and types of files that you need helps determine the storage capacity that you need. The removable storage devices you might consider installing for a notebook computer are a floppy disk drive, an additional hard drive, a CD-ROM drive or writable CD (CD-RW) drive, a DVD drive, or a DVD-RW drive. The basic steps for installing all of these devices are very similar. You perform the following steps to install a CD-ROM drive or a DVD drive for a notebook computer:    

Step 1 Step 2 Step 3 Step 4

Step 1 The first step in installing a device such as a CD-ROM or DVD drive is to turn the notebook computer off. Check the notebook's user manual to ensure you power down in the correct mode. You should then remove any external cords and cables. Step 2 You turn the computer over and remove the battery pack. Step 3 You insert the drive into the free bay, pushing firmly but carefully to ensure a solid connection. Step 4

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Once you've inserted the drive, you replace the battery, turn the notebook computer right side up, and reconnect any external cords and cables.

You have now completed the installation. In some notebooks, you can add an additional hard disk drive (HDD) using a free expansion drive bay. The procedure would be quite similar to adding a CDROM or DVD drive. On other models, you may have to remove some component first, such as a built-in floppy disk drive to reveal the free bay into which the additional HDD can be inserted. Once you've inserted a device such as a new CD-ROM, DVD or HDD in a notebook computer and powered it up, it should recognize the newly inserted device automatically. The procedure for removing a storage device such as a CD-ROM or DVD drive from a notebook is very similar to adding a new drive. Once again, you ensure the notebook is in the correct mode, remove any cables, turn it over, and remove the battery pack. Now you must locate a latch or lever which holds the drive in place, release it, and slide the drive out of the bay, The bay is now free, so you can insert a new or replacement drive. A notebook computer can connect to an external floppy disk drive (FDD) via its universal serial bus (USB) port. However, some notebook models may use other ports. The external FDD is connected to the port via a cable

3. Installing PC cards PC cards – also known by their older name, Personal Computer Memory Card International Association (PCMCIA) cards – are a common way of connecting a notebook computer to peripheral devices. They were originally intended as memory cards, but they now can provide almost any functionality a notebook requires. For example, they can be used as network cards, or to enable access to highspeed, high capacity, external HDDs. They may also provide FireWire connectivity, which is essential for digital movie editing. PC cards can be used for wireless communication between a notebook and wireless enabled components such as a keyboard or a mouse. This kind of wireless connectivity can also be achieved using the USB port. Most modern notebook computers have two PC card slots – positioned one above the other. These slots can accommodate two Type I and Type II cards, but only a single Type III card. Most notebook computers support hot-swapping of PC cards, which means that you can insert a new PC card while the computer is running and you do not need to restart it.

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To install a PC card in a notebook computer, you perform the following steps:    

Step 1 Step 2 Step 3 Step 4

Step 1 The first step in installing a PC card is to check that the notebook computer is in the correct mode. With some models, if you remove the card in a particular mode, you may damage the card. Unlike other devices, PC cards are hot-swappable, so you may not have to power down. You should check the user manual of the notebook for more specific guidelines. Step 2 Once you've checked that the notebook is in the correct mode, you firmly insert the PC card into a free slot, label facing up, so that the edge of the card lines up with the side of the computer. If the card is a Type III card, it takes up both slots. Step 3 Once you've inserted the PC card, you can check the configuration in the hardware setup window (System tray) to ensure that it's suitable for the PC card. Step 4 Check the configuration in the hardware setup window (System tray) to ensure that it's suitable for the PC card. Then lock the card into position.

To remove the PC card from a notebook computer, you move the lever or slide beside the card into the unlocked position. Once you have done this, you may have to disable it via the notebook's operating system. You disable a PC card differently depending on the model of notebook and the operating system installed. With some notebooks, running Windows 2000, you have to disable a PC card by the Unplug or Eject Hardware icon in the System tray. To disable a PC card in Windows XP, you may have to click the Safely Remove Hardware icon in the System tray. Once you have disabled a PC card, you press the eject button of the PC card you want to remove to extend the button. Then you press the extended button, so that the PC card pops out of the slot. You can then grasp it to remove it.

Summary A notebook computer uses a smaller memory module – such as a 72-pin or 144pin SO-DIMM or the 160-pin SO-RIMM – than a desktop computer. General steps for installing a memory module include turning off the notebook computer and disconnecting all external cables, removing the battery pack, inserting the memory module correctly into the memory module bay, and then reconnecting cables before turning the notebook computer back on. You can remove a module in a similar fashion. Examples of removable storage devices that you can install for a notebook

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computer include a CD drive, a DVD drive, and a second hard disk drive (HDD). The basic steps for installing any of these devices include switching off the notebook computer in the correct mode and removing the battery pack, inserting and securing the new drive in the empty bay, and then reconnecting the computer. A popular way of connecting a notebook computer to a range of peripheral devices is a PC card, also known as a PCMCIA card. You insert a PC card in the PC card slot of the notebook computer. A PC card can connect a notebook computer to a modem, a sound card, and a FireWire connection for digital movie editing.

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DIAGNOSING AND TROUBLESHOOTING Troubleshooting the system board 1. System board symptoms A system board problem may result in complete system failure or in the failure of a device and the CPU to communicate. To troubleshoot a system board problem, you perform the following basic steps:    

observe problem symptoms record any error messages check the manual check the complementary metal-oxide semiconductor (CMOS) settings

observe problem symptoms You observe the symptoms of a system failure and the conditions under which it occurred to help you identify its cause. record any error messages You note any error messages that display onscreen, or any beep codes that the system produces because these may help identify the problem and its cause. check the manual After you note any error messages, you check the User manual for the system board for an explanation of any beep codes and error messages, and the correct configuration options for the system board. check the complementary metal-oxide semiconductor (CMOS) settings You check the settings for the floppy disk drive (FDD) and hard disk drive (HDD) in the CMOS Setup utility for any configuration problems. In Pentium systems, you also need to check the advanced CMOS Setup factors to ensure that all system board-enabling settings – CPU voltage and clock speed – are set.

There are three types of failures associated with the system board – hardware failures, CMOS setup failures, and I/O failures. Some error messages that indicate hardware problems on the system board include       

201 error code 8042 Gate A20 Error CMOS Battery Low CMOS Checksum Failure CMOS System Option Not Set Direct Memory Access (DMA) Error Parity check error

201 error code

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A 201 error code message indicates that there is a RAM failure, or the RAM is installed incorrectly on the system board. 8042 Gate A20 Error An "8042 Gate A20 Error" message indicates that there is a problem with the 8042 keyboard controller chip or with the keyboard itself. CMOS Battery Low A "CMOS Battery Low" error message indicates that the CMOS battery and configuration settings may have been lost. CMOS Checksum Failure A "CMOS Checksum Failure" error message indicates that an error check on the data stored in CMOS memory has failed, possibly due to the failure of the CMOS backup battery. CMOS System Option Not Set A "CMOS System Option Not Set" error message indicates that the CMOS values have either changed or are missing. To correct the CMOS values, you run the BIOS setup again. Direct Memory Access (DMA) Error A "DMA Error" message indicates that the DMA controller on the system board failed the page register test, which is a Read/Write test on each of the internal registers of the direct memory access (DMA) controller. Parity check error A parity check error message indicates that a RAM error has occurred. When the system stores data, all the bits are added together, and the result is even or odd. The parity bit is then stored as either 1 or 0, depending on this outcome. When the data is read again, the parity is checked, and if the result differs to the previous result, a Parity Error is generated.

The "Display Switch Setting Not Proper" message indicates that the system failed to verify the display type. This is because the switch setting that selects the video mode on the motherboard was not configured correctly. Symptoms that indicate a hardware failure on the system board include     

failure to boot, although the On/Off lights are visible and the hard drive spins up failure to boot and no disk drive action, although the On/Off lights are visible and the monitor still provides a display the system freezes during normal operation the system behaves inconsistently and does not maintain the correct date and time the system produces beep codes of different lengths – one, two, three, five, seven, or nine beep codes, or one long beep and three short beeps

In an American Megatrends Inc (AMI) BIOS, the following error messages indicate specific CMOS setup errors:    

CMOS Display Mismatch CMOS Inoperational CMOS Memory Size Mismatch CMOS Time and Date Not Set

CMOS Display Mismatch

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A "CMOS Display Mismatch" message indicates that the system is unable to confirm the type of display installed for it. CMOS Inoperational A "CMOS Inoperational" message indicates that the CMOS shutdown register was unsuccessful. CMOS Memory Size Mismatch A "CMOS Memory Size Mismatch" message indicates that the system configuration and setup was unsuccessful because the BIOS setting for the total amount of memory was different to that detected in the hardware. CMOS Time and Date Not Set A "CMOS Time and Date Not Set" message indicates that the date and time stored in the CMOS memory was not set up. This message usually occurs when you boot up a system with a new motherboard for the first time, but it can also occur with an existing motherboard.

IBM-compatible error codes are errors other than CMOS setup errors. An IBMcompatible error code, which is a numeric code, indicates that a configuration problem – a memory error, a broken keyboard, or a bad hard drive controller – has occurred. A system board I/O failure prevents the system board from communicating with peripheral devices, such as the keyboard, FDD, or HDD. To test for this type of failure, you should replace the affected device with a known good one. If the new device also fails to work, it indicates an I/O fault with the system board rather than a fault with the device.

2. Configuration and hardware checks A configuration problem usually occurs when a system is set up for the first time or when new hardware has been installed. If settings in the CMOS that enable specific components to function are incorrect, the corresponding hardware will fail. These settings include options that enable the disk drives, keyboard, onboard serial and parallel ports, and video display. You check the settings on the BIOS and Chipset Features screens of the CMOS Setup utility. The CMOS Setup utility allows you to create parity or nonparity memory operations, and to turn some sections of the system's RAM on or off for shadowing purposes. Modern system boards provide an autoconfiguration function that enables a system to configure setup options automatically. The autoconfiguration function provides two options:  

BIOS defaults power-on defaults

BIOS defaults

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You use the BIOS defaults option to replace existing CMOS settings with a default set of settings from the BIOS. You do this if you enter incorrect configuration settings, and you cannot determine which setting is causing a problem. This option is also useful as a starting point for optimizing system settings. power-on defaults The power-on defaults autoconfiguration option replaces any settings that a user entered in the CMOS Setup registers, which are the storage locations in the CMOS RAM, with default settings from the BIOS. It also disables the cache and sets wait states, which are the number of CPU clock cycles that must be inserted into the memory access process, to the maximum setting so that only the most basic system components start up. If you select this option and a system still fails to start up, it indicates a hardware problem rather than a configuration error. This is the most effective way to detect a BIOS-related system problem.

The autoconfiguration function makes user intervention in the setup process unnecessary, but doesn't optimize the performance of a system. To set optimal parameters manually, you first have to disable the function. If incompatible CMOS settings cause a system to fail to respond, in some instances you can restore basic settings using  

the BIOS Delete key jumpers

the BIOS Delete key In some BIOS implementations you can hold down the Delete key in the BIOS during startup to erase the existing settings that users have selected in the CMOS. You can then reconfigure these settings. jumpers In some BIOS implementations, you can reconfigure jumpers – pins on the system board that you can connect using a shunt to close a circuit between them – to replace existing CMOS settings with basic, default settings from the BIOS.

If the CMOS configuration settings are correct but a problem persists, you need to investigate a possible system hardware failure. Testing for a hardware-related problem includes checking for   

faulty connections appropriate voltage levels device problems

faulty connections You first check the system board for physical problems, including loose or damaged cables between the system board and the power supply, and between the board and peripheral devices such as the HDD or FDD. Bends or folds in a cable may indicate that it is damaged. Intermittent errors, rather than a complete failure, suggest that a power supply or ribbon cable may be loose. appropriate voltage levels If there are no faulty connections, you check that the power supply unit is providing voltages of 5 V and 12 V DC to the system board. If the voltage levels are incorrect, you need to switch off the system and replace the power supply unit. device problems

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If the voltage levels are correct, you check that the hardware devices that connect to the system board are working. You do this by removing and installing each device, one at a time, to isolate a defective device.

3. Troubleshooting field replaceable units Field replaceable units (FRUs) are devices that you can replace, either because they malfunction or to upgrade a system. FRUs on the system board include the CMOS battery, integrated circuits (ICs), microprocessor, RAM modules, and the ROM basic input/output system (BIOS). If FRUs malfunction, a computer may produce a continuous beep tone or a blank display, and indicator lights may be off. Specific system errors indicate problems with the    

CMOS backup battery Microprocessor RAM ROM BIOS

CMOS backup battery If a system continually fails to maintain date and time information, it indicates that the CMOS backup battery is faulty, and you should replace it. You should also check the contacts of the battery holder for rust. If the CMOS battery fails or if you replace it, the settings in the CMOS are lost. So after you replace the battery, you should run the CMOS Setup utility to reconfigure the settings. Microprocessor When a microprocessor fails, the system produces a single beep sound and displays a blank screen. This indicates that an internal error has disabled the CPU, and you need to replace the microprocessor. If the system constantly freezes, it indicates that the microprocessor has overheated, possibly because its fan has stopped working. If this is the case, you may need to replace either the fan unit, the microprocessor, or both. RAM RAM failures create either hard-memory or soft-memory errors. Hard-memory errors are permanent hardware failures that generate non-maskable interrupt (NMI) errors or cause the system to emit beep codes. To determine which memory module is causing a hard-memory error, you should remove the memory modules and reinstall them one at a time to isolate the defective one. Soft-memory errors are memory errors that random faults in the operation of a system cause. You can fix these errors by rebooting the computer. If a system fails to detect all physical RAM installed, it may help to swap the RAM modules around to check if the boot up RAM count, which is a check of RAM that is carried out during the POST routine, changes. When you swap RAM into a system, you must ensure that the new RAM module is of the same type as the installed RAM. You should never mix RAM types and speeds, because this can cause the system to freeze and produce hard-memory errors.

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ROM BIOS If the system board is dead or the startup sequence moves into the CMOS Setup utility but doesn't then start the boot process, the ROM BIOS is damaged. In this case, you need to replace the BIOS with one that is compatible with the system's chipset.

Summary To troubleshoot a problem with a system board, you should first observe the symptoms of the problem, note details about the error, consult the user manual, and then check the settings in the CMOS Setup utility. System board failures result from CMOS setup, hardware, or I/O errors. To enable you to troubleshoot a configuration error in the CMOS, modern systems include an autoconfiguration function. This function provides two options – BIOS defaults and power-on defaults – for replacing CMOS settings with default settings from the BIOS. To resolve a CMOS setup problem in a system that isn't responding, you can use the BIOS Delete key or configure jumpers to implement specific CMOS settings. To troubleshoot a hardware problem with a system board, you check for faults with physical connections, the power supply unit, and hardware devices. The system board consists of a number of serviceable units, called field replaceable units (FRUs). To troubleshoot FRU devices, you remove them from the system board, and then you install them one at a time to isolate the defective device. Then you replace the faulty device with a working one.

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Power supply, port, and cable problems 1. Troubleshooting the power supply unit A power supply unit converts AC power from a wall outlet into the DC power that a computer uses. It is the primary source of power for a computer. If the power supply unit fails, a computer system can't operate. Symptoms associated with power supply problems include   

no visible indicator lights no disk drive action continuous beep tone

no visible indicator lights If the power supply to a computer fails completely, a system will be dead, with no visible lights, no disk drive action, and a blank display. no disk drive action If a partial failure of the power supply occurs, there is no disk drive action and no display on screen, but the On/Off indicator lights are visible and the system fan may work. continuous beep tone If a system produces a continuous beep, it indicates a partial failure of the power supply.

If a system is dead, you perform the following steps:    



check for faulty external connections to the power supply check that the system is on check that the power cord is connected to a known good AC outlet check that the voltage switch on the outside of the power supply unit is set to either 110 or 220 volts (V), depending on the voltage used in your region check that the power supply unit is providing the correct voltages to the motherboard and system components

Note The voltage setting in the United States is 110 to 120 V. Europe and other regions use 220 to 240 V. Some computers may not power up if the system unit cover is misaligned or has been removed. This safety feature is provided by a small microswitch in the system chassis, which detects if the computer case is open or closed. When the cover is correctly aligned, it allows the switch to close, and the system can power up. A partial power supply failure may result from a 

power overload

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

system board component failure

power overload A portion of the power supply fails if it is overloaded, or one or more of the basic voltages that it supplies are missing. system board component failure If a component on the system board fails, the component cannot process, even if the system has power. A faulty capacitor across the power input of the system board can also prevent a component from functioning.

2. Port symptoms, basic and Windows checks Devices such as an external modem or printer connect to I/O ports on a computer. Problems with a device may occur because    

the attached device is inoperable the signal cable is damaged or loose the port is faulty the software is not set properly for the port

Note A port failure does not affect the main components of the system. The symptoms associated with port failures include     

a 199, 432, or 90x IBM-compatible error code message, indicating a printer port error a 110x IBM-compatible error code message, indicating a serial port error a device not found error message, indicating a poor connection an input device not working a printer's lights are on but printer not printing

Note I/O port problems do not produce many error messages, making it more important that you remember to check for port problems if devices malfunction. To check if a system is configured to detect a port, you check the port settings in the CMOS Setup utility. If the settings in the CMOS are correct, you test for physical port problems. The type of test you use depends on whether the port is  

parallel serial

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parallel To test a parallel port, you connect a loopback test plug to it and run a software diagnostic package. The loopback plug simulates a parallel device by redirecting output signals from the port into port input pins. serial To test a serial port, you connect a serial loopback test plug to it and run a software diagnostic package. The loopback plug is wired so that it simulates the operation of a serial device. You use this test to check for interrupt request (IRQ) or addressing conflicts between the serial port and other installed devices.

If you determine that a serial or parallel port is physically functional, but it fails to connect to a device, you need to check for possible configuration errors. To do this, you check the port settings and interrupt request (IRQ) settings, which may conflict with settings for other ports. You then consult the user manual for the device to determine appropriate settings for it to use with the port. You can set the port that a printer uses via the Printers icon in the Control Panel. And you can access the settings for each port using the Device Manager. In this case, you want to access the settings for the parallel printer port in Windows 98.

Note You double-click Ports (COM & LPT), and then double-click Printer Port (LPT1). The General tabbed page of the Printer Port (LPT1) Properties dialog box displays general information about the printer port. Suppose that you want to check for any IRQ conflicts with the port. You click the Resources tab. The Resources tabbed page displays the address ranges and IRQ settings for the printer port. In this case, there are no conflicts between the port and other devices. The Device Manager includes information about ports on the following tabbed pages.   

Port Settings Driver Resources

Port Settings The Port Settings tabbed page displays the character frame and speed information for a port. It has five drop-down lists – Bits per second, Data bits, Parity, Stop bits, and Flow control. In this case, the Bit per second is 9600, there are 8 data bits, Parity is set to None, there is 1 stop bit, and Flow control is Xon / Xoff. It also includes an Advanced button, which allows you to change the receive buffer and transmit buffer speeds. Driver

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The Driver tabbed page displays information about the driver provider, and the date that the driver was installed. In this case, Microsoft is the driver provider, and it was installed on the 23rd of April 1999. It includes a Driver File Details button, which allows you to view a list of the device drivers loaded for a particular device. It also allows you to update the device driver details. Resources The Resources tabbed page displays the IRQ settings and address ranges of a port. It has a Use automatic settings checkbox, which is selected. It also has a Resource type list, which displays the settings of I/O and IRQ resources available to the port, and a Conflicting device list. In this case, the I/O range is set to 03F8 to 03FF, and the IRQ setting is 04. There are no conflicts between the port and other devices, so the Conflicting device list displays the text "No conflicts."

Suppose that you want to view the drivers loaded for the printer port. You click the Driver tab. The Driver tabbed page displays information about the driver provider, and the date that the driver was installed. You want to view the drivers loaded for the port. You click Driver File Details. Alternatively, you press Alt+D. The Driver File Details dialog box displays a list of the device drivers loaded for the printer port.

3. Troubleshooting USB ports You can use a universal serial bus (USB) port to add many types of peripheral device to a computer. If a device that you know is functional fails to work on a USB port, it indicates a problem with the port. Problems that affect a USB port include errors with the configuration of the USB controller, drivers, and hardware devices. To troubleshoot a USB port problem, you first check the CMOS Setup screen to ensure that the USB function is enabled. If it is, you should use the Device Manager to ensure that a USB controller is installed for the port.

Note You must be logged on as an administrator or as a member of the Administrators group to troubleshoot USB problems in Windows 2000. If there is no USB controller installed for a USB port or the Device Manager displays a yellow warning icon next to the controller, you need to update the system BIOS. If the USB controller does appear in the Device Manager, you should check its properties for a possible configuration error. Once you've ensured that the BIOS and controller settings are in order, you need to check the properties of a USB port driver for possible configuration errors.

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To do this – in Windows 2000 for example – you use the Device Manager. In the Device Manager, the USB ports are grouped in the USB root hub. You double-click Universal Serial Bus controllers, and then double-click USB Root Hub. The USB Root Hub Properties dialog box provides general information about the hub. You click the Driver tab to check the properties of the USB port driver. You then want to view the properties of the drivers loaded for the USB port. You click Driver Details. Alternatively, you press Alt+D, and then you press Enter. The Driver Files Details dialog box displays all the driver files loaded for the USB port. In this case, the USB port driver is C:\WINNT\system32\drivers\usbhub.sys. You click OK to return to the Computer Management console. If a USB hardware device does not install automatically, it may be because there are conflicting USB drivers loaded for the device or the drivers are out of date. To resolve this problem, you can obtain updated drivers for the device from the manufacturer and install them. You now want to update the driver loaded for the USB CD writer, using the Upgrade Device Driver Wizard. In the Device Manager, you double-click HP USB CD Writer Plus to display its properties. You then need to access driver settings. You click the Driver tab and then click Update Driver. Alternatively, you press Alt+P and then press Enter. The Welcome screen of the Upgrade Device Driver Wizard displays. And you click Next to continue. On the Install Hardware Device Drivers screen, you can search for a suitable driver or display a list of compatible drivers for the USB device. The Search for a suitable driver for my device (recommended) option is selected by default. You want to search for a suitable driver, so you click Next. On the Locate Driver Files screen, you can specify a search location for the new driver. You select Specify a location, and then click Next. Alternatively, you press Alt+S and then press Enter. The new driver is located in the Downloads folder. So you need to specify this location in the Upgrade Device Driver Wizard dialog box. You type C:\Downloads in the Copy manufacturer's files from text box and then click OK.

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The Driver Files Search Results screen informs you that the wizard has found the driver for the USB CD writer, as well as other drivers that are suitable for it. You want to view a list of these drivers, so you select Install one of the other drivers and then click Next. The Driver Files Found screen displays a list of suitable drivers for the USB CD writer. In this case, you want to load the driver in the Downloads folder. You select HP USB CD Writer 8200e series and then click Next. Alternatively, you select HP USB CD Writer 8200e series and then press Alt+N. The wizard is complete, and the new driver has been installed. So you click Finish.

4. Troubleshooting infrared ports An infrared port enables you to connect a device that uses infrared signals – rather than cable – to communicate with a computer. If there is no communication between an infrared port and a device, you should check that the device supports infrared communication. If you cannot establish infrared communication between two devices, you perform the following steps:   

check the distance between the devices check that there are no obstructions between the devices check that the devices are not exposed to direct sunlight

check the distance between the devices Infrared devices must be no more than a meter apart to transfer infrared signals successfully. In some cases, devices may need to be closer together than this. check that there are no obstructions between the devices You must ensure that the infrared ports on the two devices are facing each other, and that there are no obstructions between them that could interfere with the transmission of infrared signals. check that the devices are not exposed to direct sunlight You must check that the two devices are not exposed to direct sunlight because this may interfere with the infrared light passing between them.

Once you've ensured that infrared devices are correctly positioned, you check the properties of the devices using the Device Manager. Suppose that you've opened the Device Manager in Windows XP, and you want to check that your system is configured correctly for the device. You double-click Infrared devices, and then double-click Serial Cable using IrDA Protocol. The General tabbed page of the Serial Cable using IrDA Protocol Properties dialog box identifies the infrared device and confirms that it is working properly.

5. Troubleshooting FireWire ports

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FireWire is a high-speed serial data bus that can move large amounts of data between computers and devices. It is defined by the Institute of Electrical and Electronic Engineers (IEEE) 1394 standard. If a problem occurs with a FireWire port, you check for cable problems, hub connection problems, and power overloads. If a device connects to a hub with FireWire ports and the hub has a power cord, you must ensure that the power cord is plugged into a functioning outlet. You must also make sure that the hub's cable is properly connected to your computer. If a problem persists you can try plugging the device into another port on the hub or replace the hub. A power overload may cause a device connected to a FireWire port to shut down. If this occurs, you should disconnect the device immediately to avoid damaging the computer. If a device connected to a FireWire port fails to work, you perform the following steps:     

Restart the software application Check that all FireWire devices are on Check the faulty device Check the length of the connecting cable Check the documentation for the device

Restart the software application If you are using a software application with the device, close the application and then restart it. Check that all FireWire devices are on Ensure that all FireWire devices are turned on, and then disconnect and reconnect the faulty device. Check the faulty device Switch the FireWire device off and then on again. Check the length of the connecting cable Check that the connecting cable is no longer than 4.5 meters, and ensure that you've installed all the software that accompanied the device. If the connecting cable is longer than 4.5 meters, data transfer errors may occur or the software and the device may fail to communicate. Check the documentation for the device Check the documentation for the device for more information, and then contact the device manufacturer.

Summary To troubleshoot a dead system, you first check for faulty external connections to the power supply, and check that the system is on. You then check that the system is connected to a known good AC outlet. Then you check that the voltage switch is set to either 110 or 220 volts (V), and that the power supply unit is providing the appropriate voltages. To troubleshoot serial or parallel port problems, you first check the settings in the

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CMOS Setup utility. You also use loopback tests to check that a port is functional. You check the properties of the port using the Device Manager or – for a parallel port – the printer properties or the Printer troubleshooter. Universal serial bus (USB) port problems relate to problems with the USB controller, drivers, or peripheral devices. To troubleshoot a USB port problem, you first check that the USB function is enabled in the CMOS Setup utility, and that the Device Manager is detecting a USB controller. Then you check that the USB device installs automatically. If not, there may be a problem with the USB drivers loaded for this device, and you should update them. If infrared devices fail to communicate, you need to check that they have a clear line of sight and are positioned within 1 meter of one another. To check that a system is detecting an infrared device and that the device is working correctly, you access its properties via the Device Manager. FireWire is a high-speed serial data bus that can move large amounts of data between computers and devices. To troubleshoot FireWire problems, you need to check for faults with connecting cables and with the hub, and for possible power overloads.

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Peripheral and display device problems 1. Troubleshooting scanners and tape drives Current scanners are most likely to use universal serial bus (USB) or FireWire ports to connect to the computer system. However, traditionally, scanners often used expansion cards for this purpose. Often these cards are full small computer system interface (SCSI) adapter cards or use a simplified version of SCSI. Problems can arise if the configuration of these cards conflicts with other adapter cards or system resources. To troubleshoot a scanner, you check the following system resources:   

direct memory address (DMA) channel I/O address interrupt request (IRQ)

direct memory address (DMA) channel A DMA channel is a route via which data transfers directly between a device and memory, bypassing the CPU. An incorrectly configured DMA channel will prevent a device from communicating with a system. If a DMA channel that is used by one expansion card is chosen by another expansion card, it will become nonfunctional, and the system will not be able to communicate with the scanner. I/O address An I/O address – or port address – is a unique number that identifies a device. An incorrect I/O address will prevent the CPU from accessing a device. interrupt request (IRQ) An IRQ is a line that a hardware device uses to signal the CPU when it requires attention. Each IRQ line has a number that identifies it. An IRQ conflict occurs when you assign the same IRQ address to multiple devices. This can prevent a system from communicating with a scanner. IRQ conflicts with network interface and sound cards are the most common problems associated with scanners.

Symptoms that indicate an IRQ conflict as the cause of an incorrectly configured scanner interface include  

failure to scan, although the scanner is activated and the scanner lights are visible a misaligned scanned image on the screen

To troubleshoot a problem with a tape drive, you need to check the following components:  

controller power connection

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  

signal cable tape tape drive's operating software

controller You should check that the controller is configured correctly so that it doesn't prevent a system from recognizing the drive. power connection You check that there is a valid power connection from the power supply to the drive. If the drive is internal, the system's internal power supply unit should supply its power. If the drive is external, it must be connected to an AC outlet via a power cord. signal cable You check that the drive uses the appropriate signal cable. If the drive is a small computer system interface (SCSI) unit, it should use a SCSI cable. If it is an Integrated Drive Electronics (IDE) unit, then it must use the correct ribbon cable. tape You check that the capacity of the tape is formatted to suit the capabilities of the drive. tape drive's operating software You check that the tape drive's operating software includes a device driver and the backup software. The device driver enables the operating system (OS) to communicate with the tape drive. The backup software contains the tools required to perform backups and restore files, and to format media.

Common tape problems include    

incorrect formatting incorrect insertion into the drive physical damage write-protection

incorrect formatting You must check that the tape is formatted correctly so that it can be used with a specific drive. If the tape is formatted incorrectly, the drive will fail to read the tape. incorrect insertion into the drive You must check that the tape is securely inserted in the drive. If it isn't, the drive will fail to read it. physical damage The tape may be broken or off the reel in the cartridge, in which case you need to replace the cartridge. If the tape is broken or off the reel in the cartridge, the drive will fail to read from or write to it. write-protection You must check that a tape which you plan to use is not write protected. When a backup is complete, you can then ensure that the tape is write-protected, so that the data on it cannot be written over.

In networked environments, the use of multiple tape drives is common.

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The most common problem that affects a tape drive in these environments is the user not having sufficient rights to back up or restore files on the network. In this case, the operating system (OS) does not allow the tape drive to access files on the network.

2. Troubleshooting input devices Causes of problems with a keyboard include the keyboard hardware, its connecting cable, and the system board – which holds some of the keyboard interface circuitry. The keys on a keyboard wear over time, which can result in keys that fail to generate characters onscreen or that get stuck. If this occurs, you need to replace the keyboard. The symptoms associated with keyboard problems include 

  

an error code of six short beeps during boot up, which indicates that there is a problem with the attached keyboard or the internal keyboard interface electronics an IBM-compatible 301 error code, which indicates that the keyboard did not respond to a software reset, or a stuck key has been detected failure of characters to appear onscreen when you enter them on the keyboard, which indicates a faulty or unplugged keyboard incorrect characters display onscreen, which indicates that the language settings are incorrect

Common keyboard problems that produce a keyboard error message include  

stuck keys unplugged keyboard

stuck keys When the system detects a stuck key, it produces an error message and a beep sound. In this case, you can detach the affected key from the keyboard and replace it with the same key from another, similar keyboard. unplugged keyboard An unplugged keyboard, or a keyboard with a bad signal cable, produces a keyboard error message during startup. If the keyboard is unplugged, you should make sure that it is plugged into the correct socket on the computer's back panel.

If the keyboard produces the incorrect characters on the display, it isn't installed properly or is incompatible with the system. Alternatively, it may be using the incorrect language settings. You check and correct these settings using the Device Manager. If you suspect a keyboard hardware problem, you should replace the keyboard with one that you know is functioning correctly. If the new keyboard works, the original keyboard is faulty.

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If the new keyboard fails to work, you need to troubleshoot the keyboard controller section of the system board. If the keyboard controller is faulty, you need to replace the system board. To service a faulty keyboard, you   

remove the back cover from the keyboard check for the presence of a fuse in the 5 V DC supply check the fuse for continuity

Note You cannot hot swap a standard 5-pin DIN or a 6-pin PS/2 mini-DIN keyboard. Disconnecting or plugging in these keyboards when a system is still on may damage the keyboard and the system board. Problems associated with a mouse usually involve the trackball. When you move the mouse across the table, the trackball picks up dirt or lint, which interferes with its movement. This causes the cursor to freeze or jump periodically onscreen. To remove the trackball, you twist the latch at the bottom of the mouse in a counterclockwise direction. Then you remove the dirt from the rollers, and wipe the trackball with a lint-free cloth. To troubleshoot a faulty mouse, you first replace it with a mouse you know functions correctly. If the new mouse works, the original mouse is faulty. If the new mouse doesn't work, the problem lies either with the driver software for the mouse or with the port that the mouse uses.

Note When replacing a mouse, you must ensure that the replacement mouse uses the correct connector type for a system. So if the PC has a PS/2 mouse port, for example, you must check that the replacement mouse is a PS/2-compatible mouse. To troubleshoot the driver software and port that a mouse is using, you  

reboot in Safe mode check settings in the CMOS Setup utility

reboot in Safe mode You restart the system, and move into Safe mode by pressing the F8 function key when the "Starting Windows" message displays. This action will start the OS with the most basic mouse drivers.

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You use the Device Manager to check that the IRQ and address range settings of the mouse matches that of the port it uses. check settings in the CMOS Setup utility If a mouse fails to operate in Safe mode, you restart the system and check the CMOS Setup screen during boot up for the presence of the port that the mouse connects to.

Suppose that you want to check the IRQ settings for the mouse and the port in Safe mode, using Windows 98. To do this, you use the Device Manager. You double-click Mouse, and then double-click PS/2 Compatible Mouse Port. The General tabbed page of the PS/2 Compatible Mouse Port Properties dialog box provides information about the mouse, its type and manufacturer, and its status. You want to check the IRQ setting for the mouse. You click the Resources tab. The Resources tabbed page provides information about the system resources that are assigned to the mouse. The IRQ setting for the mouse in this case is 12. Once you've checked the setting, you click OK to close the dialog box and return to the Device Manager.

3. Troubleshooting display devices Because the inside of a monitor contains very high voltages – up to 25,000 V – only experienced technicians should open it. Even if you unplug a monitor, its circuitry stores high-voltage potentials. Inside a monitor, a high-voltage anode connects a cathode ray tube (CRT) to the high-voltage sections of the signal-processing board. Using a monitor without its cover is also hazardous for this reason. Before handling the CRT tube, you must discharge the anode of the picture tube to the monitor's chassis. To ground the built-up charge on the anode, you use a large, long-handled screwdriver and a shorting clip to protect against shock. When handling the CRT tube, you must   

never lift the CRT tube by the neck to remove or replace it prevent the neck of the tube from striking any surface because the CRT tube is fragile wear protective goggles because if the CRT tube cracks, the inrush of air will cause a high-velocity implosion, and the glass will shatter

To troubleshoot a monitor, you perform the following steps: 

check the power supply and display settings

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 

disconnect the signal cable exchange the monitor with a known good one

check the power supply and display settings You first check the power cord to see that it is plugged in. Then you check that the monitor's power switch is on. You should also check the display settings, which establish the brightness, contrast, focus, and screen size of the display, on the front panel of the monitor. If these settings are incorrect, the display may be blank or it may show fuzzy characters, incomplete images, and poor or missing colors. disconnect the signal cable Once you've checked that the monitor is receiving power and that display settings are appropriate, you disconnect the monitor's signal cable from the video adapter. If a raster – or image – appears, it indicates that the video card is faulty. exchange the monitor with a known good one If the fault doesn't lie with the video card, you should exchange the monitor with a working one. If the new monitor works, the original monitor is the cause of the problem.

If fuzzy characters display on a monitor, you first reset the display resolution to the default video graphic adapter (VGA) values. If the problem persists, you check the intensity and contrast controls on the front panel, in case incorrect settings are responsible. Finally, you remove built-up electromagnetic fields, which cause display problems, from the screen through a process called degaussing. Most modern monitors have a degaussing button or menu option. A touch screen is a computer display screen that uses a touch-sensitive transparent panel to sense touch. This allows you to interact with a computer by touching items on the screen to select or move them. To troubleshoot a touch screen, you first need to determine whether the cause of the problem is the   

Display Hardware Software

Display The easiest way to test if the touch screen display itself is the cause of a problem is to replace it with a touch screen you know is functioning correctly. If the replacement screen works, the problem is with the touch screen hardware. If it doesn't, you need to investigate other problem causes. Hardware Hardware problems include faults with the cabling, controller, power supply, or integration of the touch screen components in the display. To verify problems with cabling, controller, or power supply, you substitute them with working units. Software If a touch screen transmits incorrect touch coordinates it indicates a problem with the calibration of the touch screen.

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To calibrate the touch screen, you run the calibration routine included with the driver or application software and digitize or touch the points on the screen when they are indicated.

Summary To troubleshoot a scanner, you check for configuration errors with a direct memory address (DMA) channel, the I/O address, and the interrupt request (IRQ) setting for the scanner. To troubleshoot tape drives, you need to check the controller, power connection, signal cable, tape, and the tape drive's operating system. The keyboard and mouse are the most common input devices. To troubleshoot a keyboard, you check for faults with the physical keyboard, its connecting cable, and the system board. Problems associated with the mouse usually involve the trackball, but you also need to check the driver software and port that it uses as possible causes of an error. To troubleshoot a monitor, you first check that it is on and that the contrast and brightness settings aren't set too low. Then you disconnect the signal cable to test the video card, and, if necessary, check the monitor by replacing it with one you know works. To troubleshoot a touch screen problem, you need to determine whether the problem is related to the display, hardware, or software.

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Networking, modem, and SCSI problems 1. Troubleshooting a NIC A problem with a network connection can have several effects. For example, you may not be able to establish a connection to the network, or the Network Neighborhood may not show any other computers. If the problem is related to the NIC itself, you might have received an error message when installing the drivers for this device, or a warning message or icon may appear in the Device Manager. Most NICs, such as a PCMCIA network card, have indicator lights, one of which should be steady to indicate a good connection. The other light should be blinking, indicating activity on the network. If both of these lights are off, there is a problem with the NIC, the network cable, or the device (a hub, for example) to which it is connected. If a networking problem occurs, you should first check whether other computers in the same network are having the same problem – the whole network may have gone down. If the network is up, you should try rebooting the PC to reset network connections. If the network is controlled by a domain server, you will need to log off before rebooting, so that the server will not think you are still logged on. If rebooting fails to correct a network problem, you should check    

the basic input/output system (BIOS) the network cable device conflicts NIC drivers

the basic input/output system (BIOS) You should check that you have the latest version of the basic input/output system (BIOS) for your motherboard to help avoid network problems. If necessary, you can get information on BIOS upgrades from the motherboard's manufacturer. the network cable If you connect the cable to another port on the hub and it still doesn't work, this may indicate a cable problem, or a problem with the NIC itself rather than the hub. For the network cable, you should check that it is not damaged, and that the cable is not longer than the maximum allowed length for the type of network. device conflicts A legacy network card that cannot connect to the network might have a device conflict. You should check the conflicting device list in the Device Manager to determine if this is the case. Typically, the Device Manager will show a yellow exclamation mark (!) next to the name of the NIC if it is experiencing a resource conflict. A red X will appear if it has been disabled, to prevent problems occurring with other installed devices.

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NIC drivers You should check the NIC in the Device Manager to make sure that the correct drivers are installed. Then you should try uninstalling and reinstalling the NIC drivers in case the drivers are corrupt.

A network connectivity problem may result from the network protocol used, which for most networks is TCP/IP (Transmission Control Protocol/Internet Protocol) rather than from a fault with a physical component. You can obtain information about the TCP/IP configuration on a local machine using the ipconfig command under Windows NT, Windows 2000, and Windows XP. In Windows 9x, you can use the winipcfg command for this purpose. The ipconfig command has a number of parameters, which you use to display information or refresh settings. One of the most useful parameters is /all. To use it, you type ipconfig/all at the command prompt and press Enter. If TCP/IP is correctly configured and an IP address is assigned, the adapter address, IP address, subnet mask, and default gateway display on the screen. If the PC cannot reach the DHCP server, and it is using dynamic IP addressing, it will assign itself an IP address in a process called IP autoconfiguration.

If this happens, the ipconfig command will display the IP autoconfiguration address, which begins with 169, instead of the IP address.

Note The Dynamic Host Configuration Protocol (DHCP) is a protocol that automates the TCP/IP configuration process. You can release and renew IP addresses with the ipconfig command, which may help in resolving DHCP problems. You can release the current IP address using the ipconfig/release command, and lease a new address using the command ipconfig/renew. To test the TCP/IP configuration of a Windows 9x PC, you select Start - Run, and type winipcfg in the Open text box. You can use the Release, Release All, Renew, and Renew All buttons to release the IP address and get a new one. Windows includes diagnostic command-line tools that you can use to test TCP/IP. The ping command allows you to test the IP address of a local or remote computer by sending a signal to it. If the computer receives the signal successfully, it responds. The first step in using the ping command to test TCP/IP is to check if the protocol is installed correctly on the local PC. To test the TCP/IP configuration of your computer, you perform a loopback address test. You enter the command

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ping 127.0.0.1 at the command prompt. The IP address 127.0.0.1 is the loopback address, and is reserved for your own computer. If TCP/IP is correctly configured, you receive a reply from your computer. If you get errors at this point, you should suspect a problem with the TCP/IP configuration on your PC. In this case, you should check that the NIC and the TCP/IP protocol suite are correctly configured. You should remove and reinstall each networking-related component to determine when error messages occur, and compare your own configuration with that of a PC on the network that is fully operational. If you can ping the local PC successfully, you should then try to ping the address of your default gateway, which your network administrator can provide. If this doesn't work, the problem may lie with the gateway, or with the network to the gateway. If you can ping the default gateway, you should try to ping the host computer you are trying to reach. If this computer does not respond, the problem may lie on the host, or on the network to that host. In some situations, you may be able to ping the host's IP address, but not the domain name for this address. For example, you may be able to ping 209.127.100.1, which is the IP address for www.interswift.com. To try to communicate with the mainInterswift host, you type ping www.interswift.com at the command prompt and then press Enter. The ping command using the domain name is unsuccessful, but when we used the IP address corresponding to this domain name, the ping command succeeded. Such a situation indicates a problem with the DNS configuration or DNS server.

2. Troubleshooting SCSI devices When you install and configure small computer system interface (SCSI) devices, you should consider   

component quality cable length the order in which you install devices

component quality All the SCSI components you use should be of a good quality. For example, you should use highquality cables to prevent data degradation and interference, and high-quality active terminators instead of passive ones. cable length You should keep the cable length as short as possible to prevent data from becoming corrupted and to improve performance. the order in which you install devices You should add extra SCSI devices one by one. It is a good idea to install the SCSI host adapter first, and then the SCSI hard drive. Once these are working, you can start to install other SCSI devices.

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You should keep records of all installations and SCSI configurations, so that you can use this information when troubleshooting. You should also keep track of switch and jumper settings for all your SCSI devices, and record the addresses that the SCSI host adapter uses. If you have problems when installing SCSI devices, you should check the     

BIOS connections external devices host adapter terminators

BIOS If you are using a SCSI host adapter, you should place it in one of the Peripheral Component Interconnect (PCI) slots, rather than say an Industry Standard Architecture (ISA) slot. If your host adapter is in a PCI slot, you should ensure that you have the latest BIOS version for your motherboard so that these slots work correctly. connections You should check the connections to all the SCSI devices and power connections to eliminate faulty connections as a cause of problems. If you remove and reattach the cables, you may resolve connection problems. external devices You should turn on all external SCSI devices so that the SCSI drivers will find them when the computer boots up. You should also check that the latest drivers for the SCSI devices – both internal and external – are installed. host adapter You should place the host adapter into a PCI slot that supports bus mastering. On older motherboards, not all PCI slots support this. To resolve this, you can try moving the host adapter to another PCI slot. terminators Both ends of a chain of SCSI devices must be terminated, and all other points in the chain should have termination disabled. So if the host adapter is at the end of the chain, you should enable termination, and if it is in the middle, you should disable termination.

If you have Integrated Drive Electronics (IDE) devices on your system, your computer will try to boot from the IDE drives before booting from the SCSI drives. If you want to boot from a SCSI drive, you must either remove the other drives or change the boot order in the BIOS. If you have only SCSI drives on a system and the computer won't boot, you should check that the BIOS drive configuration is set to "No Drives Installed". Most BIOS versions support only IDE drives, and will try to boot from another device only if no drives are specified in the BIOS setup. If you've confirmed the correct BIOS settings and a problem with a SCSI device still occurs, you should check that the SCSI drive is partitioned, that it has a primary partition, and that its boot partition is set as the active partition.

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If it still doesn't work you can back up the drive and perform a low-level format of it with the format utility provided with the host adapter.

3. Troubleshooting a modem Problems with a modem may cause it to fail to install, respond, dial out, connect after dialing, transmit data, or terminate a session. After installing a modem – particularly an external modem, which is likely to use the serial port – it's a good idea to check for device conflicts with other devices. Remember that if you install a non-Plug and Play (PnP) device on a COM port, you should disable the port because the system won't detect that this port is used and so might try to reallocate it. Once you've checked for device conflicts, you troubleshoot both internal and external modems by checking physical connections, such as the telephone line, the modem's software configuration, and device drivers. Many modems can perform the following loopback tests, which are useful if frequent transmission errors occur.   

remote digital loopback test local digital loopback test local analog loopback test

remote digital loopback test You should run a remote digital loopback test first. In effect, this test causes the data sent to a remote modem to be reflected back to the local modem. So it checks that the local modem is sending and receiving data properly and the line connection between the modems. As a result, if this test is successful, you can assume the reason for any transmission errors lies with the remote host you are trying to reach. local digital loopback test If the remote digital loopback test fails, you should run a local digital loopback test (with a selftest). The self-test checks the circuitry of the modem itself, whereas the digital loopback test checks the cable connecting the PC to the modem. If these tests run successfully, the problem may be with the configuration at the local computer. local analog loopback test If a local digital loopback test fails, you should run a local analog loopback test, which tests both the analog and the digital circuits of the local modem. If this fails, the problem is with the local modem.

In all versions of Windows, you can access a modem's configuration information from the Control Panel. Suppose that you are running Windows 98 and need to find out the port and maximum speed settings of the modem installed on your PC. You first doubleclick the Modems icon in the Control Panel. You then access the properties of the modem. You click the Properties button on the General tabbed page of the Modems Properties dialog box. The General tabbed page of the Standard Modem properties dialog box displays the port and maximum speed settings.

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Now you want to check the connection preferences set for the modem. You click the Connection tab in the modem's Properties dialog box. The Connection preferences section allows you to control how data is sent and received by the modem. You can define the number of data bits in a word (almost always 8, but sometimes 7 on legacy systems), the parity (how the modem checks for errors), and the number of stop bits (most protocols require a single stop bit). The Call preferences section of the Connection tabbed page enables you to configure a modem to wait for a dial tone before dialing, cancel a call if it's not connected within a specified time, and disconnect a call if it's idle for more than a specified amount of time. You click the Advanced button on the Connection tabbed page to access additional modem settings. The Advanced Connection Settings dialog box shows you the modem error and flow control, and provides modulation settings. You click OK to close the Advanced Connection Settings dialog box. And you click OK again to close the Properties dialog box. The Diagnostics tabbed page of the Modems Properties dialog box gives you access to information on the modem's drivers. To check the driver that the modem is using, you select the modem, and then click the Driver button. The driver information displays. The HyperTerminal is an application that is shipped with all versions of Windows. You can use it to connect to Bulletin Board Systems (BBSs) and Telnet sites using your modem. However, you can also set it up to talk directly to your modem, so as to configure it or run various diagnostic tests. To do this, you launch HyperTerminal by selecting Start - Programs - Accessories - Communications HyperTerminal. After providing a name for the connection you want to establish, specifying the port over which you wish to connect, and configuring the port settings, you are presented with the HyperTerminal window. You can enter various commands in this window to configure the modem. These commands are known as the modem command set, and the most popular is the AT command set, developed by Hayes. To place this particular modem in the command mode, you type +++. Almost all AT commands are preceded by the letters at. In this case, you decide to use the command e1, to echo commands to the screen. So you type ate1 and the modem responds with OK. You can then enter other AT commands. For example, the command at&f restores the factory default configuration.

Summary To troubleshoot a problem with a network interface card (NIC), you should check the NIC, check that the cable is correctly connected, and ensure that the rest of

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the network is functioning. You use the Device Manager to check for conflicts with other devices, and to update the drivers for a NIC. To test a computer's Transmission Control Protocol/Internet Protocol (TCP/IP) connectivity, you can use the ping, ipconfig, and winipcfg commands. When adding small computer system interface (SCSI) devices, you should use good quality cable and terminators, and keep the cable lengths as short as possible. You should add devices one at a time, and keep records of any jumper and switch settings. When troubleshooting a modem, it's a good idea to check for device conflicts first, before checking the physical connections, the modem's software configuration, and device drivers. Many modems can perform a number of loopback tests, which you can use if the modem makes frequent transmission errors. You can also use the HyperTerminal application to configure a modem.

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Resolving video and sound problems 1. Troubleshooting a sound card If problems arise with a sound card, they are likely – more than for any other adapter card or device – to be caused by the physical setup of the card and any devices attached to it. Some of the physical settings you should check if you have problems getting a sound card to work are the    

speaker connection microphone connection volume controls speaker positioning

speaker connection You should check that the speakers are plugged into the speaker port, and not the microphone (MIC) port by mistake. The correct ports will usually be indicated on the card itself. Also, you should check the condition of the wires connecting the card to the speakers. microphone connection If you cannot record sound, you should ensure that the microphone is plugged into the correct jack and that it is turned on. volume controls One of the most common causes of problems with sound cards is an incorrect volume setting. Remember that the volume can be set physically, using the controls on the device attached to the card. Some older cards have a volume control wheel on the card itself. The volume can also be set using software, via the Windows volume control or the controls associated with the application using the card. To access the Windows volume control in Windows 2000, for instance, you select Start - Programs - Accessories - Entertainment - Volume Control. speaker positioning If you have a stereo speaker system, the speakers might be positioned the wrong way around – the speaker which should be positioned on the right is on the left, and vice versa. In this case, a problem occurs when you try to adjust the balance. To fix this, you switch the positions of the speakers.

As with other devices, sound cards may cause conflicts with other devices. These conflicts –two devices might be using the same IRQ channel for example – might not affect your system except when both conflicting devices are in use. You use a software diagnostic utility like the Device Manager, which you access through the System icon in the Control Panel, to check for such conflicts. Suppose that you want to check that your sound card, installed on a PC running Windows 98, is not causing a conflict with another device. In the Control Panel, you double-click the System icon to display the System Properties dialog box. You then need to access device settings in the System Properties dialog box. Click the Device Manager tab of the System Properties dialog box.

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The Device Manager tabbed page displays a list of all the devices that are installed on the computer. You expand the Sound, video and game controllers node on the Device Manager tabbed page and double-click the entry corresponding to the sound card. The General tabbed page provides details about the sound card and its status. You click the Resources tab of this dialog box to check if the card conflicts with any other devices. Any conflicts are indicated in the Conflicting device list area of this tabbed page. In this case, the card is not conflicting with any other devices, so the text "No conflicts" appears in the list. If a sound card is causing a conflict, you should uninstall the driver, reboot the PC, and let Windows 98 detect the sound card and automatically assign the correct resources to it - if the PnP process is working properly. You can uninstall the driver for a sound card by right-clicking the entry corresponding to the sound card on the Driver Manager tabbed page and selecting the Remove option.

2. Troubleshooting video Symptoms of video problems include        

no display on the monitor the wrong characters displaying on the monitor diagonal lines a scrolling display an audible error code of one long and six short beeps, or one long and two short beeps an error message fuzzy characters on screen a monitor that displays only one color

If a video problem occurs, the first steps you should take are the simplest (and consequently the easiest to miss) – check that the monitor's power button is on and that the power cord is plugged in. You should also check that the intensity and contrast of the monitor are not turned down. Hardware checks you can perform to troubleshoot video problems are    

removing the video signal cable removing any multimedia cards, and rebooting checking the monitor components exchanging the video card

removing the video signal cable

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If you remove the video signal cable, the raster – the area of screen that produces an image – may appear. Also, many monitors are configured to display a message if there is a problem with the signal cable, or if it is disconnected. If the raster or the message appears, the monitor is fine, and the problem is system-related. removing any multimedia cards, and rebooting In some cases, video display problems can be caused by other multimedia related adapter cards. If the display is correct after you switch the system off, remove these cards, and reboot the system, one of the cards is causing the problem. You should reinstall them one at a time until the problem recurs to identify which card is at fault, and then replace this card. checking the monitor components To check whether a hardware component in the monitor is causing a video problem, you remove the signal cable from the computer unit and the power cord from the AC power outlet. Then you replace the monitor with one of the same type that you know is functioning correctly. If the display is correct when the system boots up, the fault is with the monitor you've replaced and you should send it for a service. exchanging the video card If the display is still not correct after you've replaced the monitor, you should exchange the video card inside the system case for a known good one.

If video problems do not arise from hardware faults, you should perform some software checks. The first step in isolating video problems in Windows – if you can see the desktop – is to check the video drivers. Suppose you need to check these drivers on a PC running Windows 98. You can check drivers using the Device Manager, but, for video drivers, you also have the option of double-clicking the Display icon in the Control Panel. To access information about the video drivers, you click the Settings tab in the Display Properties dialog box. Then you click the Advanced button. In the Display Adapter Properties dialog box, you can access details of the video adapter currently installed for the system. You click the Adapter tab of the video adapter Properties dialog box You click the Change button to change the display driver. Alternatively, you press Alt+C. The Windows Update Device Driver Wizard launches to allow you to check if the current driver is the most up-to-date driver for your system. . The wizard allows you to let Windows search for an updated driver, or to select a driver from a list. In this case, you accept the default selection of the Search for a better driver than the one your device is using now (Recommended) radio button and click Next. The wizard will search the drivers on your hard drive by default. It also allows you to specify whether it should search for a driver on the floppy disk drive, CDROM, the Windows Update web site, or another location you specify. In this case, you want to update the driver using a CD, which you have received from the video card manufacturer. So you select the CD-ROM drive checkbox and click Next. The wizard locates an upgraded driver for the monitor, and you click Next to continue.

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Once the wizard completes the installation, a dialog box asks you if you want to restart the computer so that the new setting takes effect. If you click Yes, your computer will reboot immediately. To install or update the drivers using Windows, you must be able to see the interface. If a video problem prevents you from seeing the desktop at all, you should restart and press F8 after the first beep. In the Windows 98 Startup menu – or in Windows 2000 and Windows XP, the Advanced Options menu – you select Safe mode, which will cause Windows to load the standard 640x480x16 color VGA driver. This is a minimum functionality video driver you can use to install the correct driver for your display.

Summary Problems with a sound card can be caused by the physical setup of the card and any devices attached to it. For example, the volume control on the speakers may be off. You use the Device Manager to check for sound card conflicts. Display problems can occur because of software or hardware problems. Once you've checked that a monitor is on, you should check that the correct driver for the display adapter is installed. Then you check the monitor, adapter cards, and video signal cable.

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Troubleshooting storage and cooling devices 1. Troubleshooting floppy disk drives A floppy disk drive (FDD) error can occur during the computer's power-on self test (POST) routine, or when you try to read a floppy disk in the drive. Floppy disk errors can have the following causes:    

Setup and operating system errors User errors Disk errors Hardware problems

Setup and operating system errors One "error" which is easily overlooked is that the application is simply pointing to a drive other than the FDD. On the other hand, genuine OS errors – unrelated to the FDD – may affect access to the drive. The basic input/output system (BIOS) setup or complementary metal-oxide semiconductor (CMOS) setup may also be incorrectly configured to support the FDD. User errors User errors that affect the FDD include inserting a floppy disk incorrectly, or using the wrong command to access the disk. Disk errors Disk errors that affect the operation of the drive include disks that aren't formatted correctly, or on which the shutter window doesn't open properly. The plastic casing of the disk itself could also be damaged in some way, or there could be foreign objects on the disk surface. Hardware problems A hardware problem may relate to the drive itself, which may not be operational. In this case, you will need to repair or replace it. If you can't read the contents of a floppy disk, this may indicate that the cable connecting the drive FDD to the motherboard is damaged, or badly connected. You should check that the colored stripe on the edge of the cable is aligned with pin 1 of the connector on the motherboard. The power supply may not be functioning, or the cable that provides power to the drive may be badly connected.

To troubleshoot FDD problems, you can carry out some basic steps, including     

check the floppy disk check the drive light check the CMOS setup settings reboot the computer clean the drive heads

check the floppy disk You should take the floppy disk out of the drive and examine it to check if the shuttle window moves properly. You should also remove any foreign objects from the surface of the disk. Then you reinsert the disk, and try to access it again. If another disk works in the drive, the problem is usually the disk, and not the drive.

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If the drive is out of alignment, however, it will be able to read disks that it formatted, but not disks that have been formatted in other drives. You should try several disks to establish if this is the case, and then replace the drive if it is. check the drive light You should check that the correct drive light comes on when you access the disk to ensure that you are not trying to access the wrong drive. If the light doesn't come on at all, you should try to access the disk using the dir a: or chkdsk a: commands. If the light still doesn't come on, the problem might be a hardware connection, such as the power cable. If the light stays on once you boot the computer but the drive isn't functioning, the ribbon cable attaching the drive to the controller is probably not correctly aligned. check the CMOS setup settings If the drive has not been used recently, it might have lost its CMOS setup data. You should access the CMOS Setup utility, check the drive specifications, and check that drives A and B have not been switched. reboot the computer You can try to reboot the machine and access the drive again. Sometimes this solves disk access problems. clean the drive heads You should clean the read/write (R/W) heads on the FDD using a head-cleaning kit that comes with a head-cleaning disk and a cleaning solution.

If the basic troubleshooting steps fail to resolve FDD errors, you have to try to isolate the hardware component causing the problem. To do this, you perform the following steps:   



turn off the computer, open the case, and check all connections to the motherboard check the power cable by replacing it with a known good one if the drive doesn't work after replacing the power cable, check the data cable by replacing it with a known good one and ensure that the stripe on the cable is lined up with pin 1 on the motherboard if replacing the cables doesn't work, the problem probably lies with the motherboard itself. Try upgrading the system ROM by flashing the ROM chip

The following error messages identify specific problems with a floppy disk:    

Not ready reading drive A General failure reading drive A Track 0 bad, disk not usable Write-protect error writing drive A

Not ready reading drive A The error message "Not ready reading drive A: Abort, Retry, Fail?" indicates that the floppy disk cannot be read. This could happen if the disk is missing or inserted incorrectly. If the disk is in the drive, it might have a bad boot record, a bad file allocation table (FAT), or bad disk sectors.

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General failure reading drive A The error message "General failure reading drive A: Abort, Retry, Fail?" indicates that a floppy disk is unformatted or severely corrupted. If the disk is the cause of the problem, it is probably unusable and should be discarded. However, a malfunctioning FDD may also cause this error message to display. Track 0 bad, disk not usable The error message "Track 0 bad, disk not usable" displays if you use the wrong disk type to format a disk. You should check whether the disk is a high-density (disk capacity 1.44 MB) or a doubledensity (disk capacity 720 KB) disk. A high-density disk has holes on both corners, whereas a double-density disk has a hole on one corner only. Write-protect error writing drive A The error message "Write-protect error writing drive A:" indicates that the disk is write-protected. To write to a 3.5-inch floppy disk, the write-protect window on the disk must be closed.

The "Non-system disk or disk error. Replace and strike any key when ready" message indicates that you are trying to boot from a non-bootable disk. This typically happens if you forget to remove a disk from the FDD when you power down your PC. When you power up again, the system looks for the OS on the FDD, doesn't find it, and the error displays. You can solve the problem in most cases by removing the disk from the drive and pressing a key to continue the boot process. If there is no floppy disk in the FDD when this message displays, some OS files are probably missing, and you should boot from a rescue disk to check whether all system files are present. The error message "Bad or missing COMMAND.COM", or an error message relating to the himem.sys or config.sys files, indicates that one of the files referred to is corrupt or missing and should be replaced. The message "Incorrect DOS version" appears when you use a DOS command, such as format or backup, that does not belong to the version of DOS you are using. You use the ver command to check which version of DOS you are using, and update the commands or the DOS version as appropriate. The "Invalid Drive Specification" message appears if you try to access a drive that the OS doesn't recognize – in other words, the OS is unaware of the drive. This can occur because you use the wrong drive letter, or because the drive has not been set up properly in the BIOS setup.

2. Troubleshooting HDDs, CD, and DVD drives Installing hard disk drives (HDDs), CD-ROM drives, and DVD-ROM drives is usually not problematic unless you have a complex drive setup – for example, if you are installing a second small computer system interface (SCSI) drive on a system with two host adapters that already has a main Integrated Drive Electronics (IDE) drive. It's usually a good idea to build up your experience of such installations – you should start with simple, straightforward scenarios and progress to more complex situations. Typical problems you might experience when installing – or immediately after installing – an HDD include 

an installed hard drive is not listed

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    

the hard drive is not found formatting and partitioning errors no boot device is available CMOS errors other components are affected by the installation

an installed hard drive is not listed If an HDD that you have installed is not listed in the CMOS setup, you should check whether autodetection is enabled. When you enable hard drive autodetection in the CMOS setup and reboot, the system should recognize the drive. the hard drive is not found If an error message tells you that the hard drive can't be found, you should turn off the PC and check the physical connections. The data or power cables may be loose, or aligned incorrectly. If the connections are fine, you should check the jumper settings. The default jumper settings are usually only correct if the drive is the only drive in the system. You should change the jumper settings to reflect whether the drive is the only drive, or the master or slave drive in a two-drive configuration. formatting and partitioning errors The failure of the system to recognize a newly installed drive may be caused by formatting errors. Almost all IDE disks are already low-level formatted, but you may need to perform this operation on a legacy drive. You may then have to carry out a high-level format, using the format command, possibly with the /s option (which makes the drive you are formatting a bootable drive). You should also check that the disk is partitioned properly, and run the fdisk utility if necessary. no boot device is available If an error message informs you that no boot device is available, there is no bootable disk in the machine – the computer cannot boot off the newly installed HDD and there is no floppy disk in the FDD. You should insert a bootable disk and reboot. CMOS errors If a message appears saying "Configuration/ CMOS error. Run setup", you should simply run CMOS setup. You can expect this error message if you have an older BIOS version that does not support autodetection. When running CMOS setup, you should also check that the system recognizes large drives (of a size greater than 512 MB). other components are affected by the installation Remember that you may inadvertently affect other components while installing an HDD. For example, you may knock a memory module loose, in which case you will hear some beeps, indicating a memory error, during the POST. Or you may have to detach, but then forget to reattach, a cable to the FDD. This will lead to the display of the appropriate error messages on screen during the boot process.

As the form factor of the various types of CD drives (CD-ROM, CD-R, CD-RW) and DVD drives (DVD-ROM, DVD-RW) are the same, you perform the same checks when installing these drives. For CD drives, you should normally check that  

the cables are connected the jumper settings are correct

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    

IDE connections are enabled SCSI IDs are set, and devices terminated the mscdex.exe file is present there are no port setting conflicts there are no boot viruses

the cables are connected You should check both the power and the data cable connections, and ensure (for IDE drives) that the data cable is correctly aligned with pin 1 on the IDE controller. the jumper settings are correct If the drive is an IDE drive, you should check the jumper settings. If the CD-ROM drive and the DVD-ROM drive are using the same IDE connections, one must be set to master, and the other to slave. If you are using only one drive on an IDE channel, you should ensure that it is set to single or master. IDE connections are enabled If you are using IDE drives, you should ensure that the IDE connections on the motherboard are enabled in the CMOS Setup utility. SCSI IDs are set, and devices terminated If you have installed a SCSI drive, you should check that the correct IDs – numbers that identify the device to the bus – are set using the jumpers or software settings. You should check the termination settings. If the drive is at the end of the SCSI chain, it should be terminated. Otherwise, termination should be disabled. You should also check that the correct SCSI drivers are installed. the mscdex.exe file is present If you are booting from a Windows 9x startup disk and require access to the CD or DVD drive, you should check that the mscdex.exe and cdtech.sys files are in the correct directory on the disk. You should also check that the references to these files are present in the config.sys and autoexec.bat files. there are no port setting conflicts You use the Device Manager to check that there are no other devices using the same interrupt (IRQ) lines and other resources, resulting in a device conflict. there are no boot viruses If you have eliminated other common causes, and your PC will not boot at all after you install a new drive, it may have been infected with a boot sector virus. You should run virus-checking software to determine if this is the case.

3. Troubleshooting cooling systems All PCs use several different methods to prevent internal components from overheating. These include fans, heat sinks, different kinds of thermal materials designed to dissipate heat rapidly, and liquid cooling systems. Fans are the most commonly used cooling system, and several fans are found in all PCs. They cool the inside of the case by continually drawing cooler air into it or, in some older systems, blowing air out of the case. If you find that your system is shutting down for no apparent reason, it may be due to overheating and you should troubleshoot the fans. You should check for 

fan operation

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  

dust case size unused expansion slots

fan operation If the fans are not actually working, they cannot cool your system. You should be able to check if this is the case by looking or listening for the fans. You should then replace any defective fans. dust You should check the area in and around the fans for excessive dust buildup, and remove any dust with a non-static vacuum. Also, you should clean the inside of the case to prevent dust buildup on the components themselves – dust acts as an insulator and can cause these components to overheat. case size You should try and use as large a case size as is practical, and even think about changing the size of the case if you plan a significant upgrade to your system. A larger case size helps to cool the system more efficiently. unused expansion slots It's important that you cover any unused expansion slots because if these are left open, they can disrupt the air flow within the case.

A cooling fan is used to cool down the CPU and, depending on the type of CPU used, sits on top of the processor or is clipped onto its side. This fan derives its power from the power supply unit. If you are having problems which you believe are related to an overheating CPU – typical symptoms include system crashes, memory errors, and lockups – then you should check the power connection. Some systems automatically shut down if the fan stops working. Older processor types use heat sinks to dissipate heat away from the CPU. These are very reliable because there are no moving parts, but not as efficient as fans. A popular solution is the use of a heat sink and a fan, sometimes referred to as a cooler. To improve the heat distribution away from the CPU, some users place a thin layer of a special material – commonly known as thermal compound or silicon compound – at the interface between the surface of the CPU and the fan, or heat sink. Other fans and heat sinks have a thermal pad, designed to eliminate the need for thermal compound. Problems can arise if these are used together, so you should check this when troubleshooting the processor cooling system. Users with high-end processors, or those who wish to overclock these processors – deliberately run the processor at a higher clock speed than recommended by the manufacturer, a practice which immediately voids the warranty – can use a liquid cooling system. Such a system circulates a liquid – such as water – around a heat sink that encloses the CPU. Because any liquid is a better coolant than air, such systems can cool the CPU much more efficiently than a fan, allowing the CPU to run faster (and therefore hotter) than would otherwise be the case. These systems have the added advantage that they run much more quietly than fans.

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Some problems you might have with liquid cooling systems on a PC include   

the pump isn't running errors display when you boot up the temperature is too high

the pump isn't running If the pump isn't running, you should check that it is receiving power. If the problem isn't the power supply, you may need to replace the pump. errors display when you boot up Some systems will not boot, or display error messages while booting, if a cooling fan – rather than a liquid cooling system – is not attached to the CPU. You might be able to disable this setting in BIOS. If not, you may have to upgrade it. the temperature is too high With a liquid cooling system, a high temperature can have several different causes. The power supply may be faulty, for example, or one of the tubes circulating the liquid may be twisted or blocked. In this situation, you may have to disassemble the system and reinstall new tubing.

Summary A floppy disk drive (FDD) error can occur as a result of a mechanical problem with a floppy disk, user error, setup or operating system (OS) errors, or hardware problems. Hardware problems include physical faults with the FDD, with cable connections, or with the power supply. Installing hard disk drives (HDDs), CD drives, and DVD drives is usually not problematic unless you have a complex drive setup. Typical problems you might encounter when installing an HDD include CMOS, boot device, and formatting errors. When installing CD and DVD drives, similar kinds of issues arise, because the form factor of the drive is the same. Among the items you should check for such drives are cable connections, jumper settings, and device conflicts. All PCs support several different methods for preventing internal components from overheating. These include fans, heat sinks, thermal materials, and liquid cooling systems

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Troubleshooting notebook computers 1. General troubleshooting procedures If a problem occurs on a notebook computer, it's a good idea to stop any work you are doing in case you cause further damage or lose data. You should then observe the problem and record information about it. You note down what you did before the problem occurred, and exactly what the system's response is to make it easier to identify the problem. You should try to be as specific as you can about which part of the system is causing the problem. One of the most important sources of information is the screen itself, so you should print a copy of the screen, using a Print Screen key, as a record. Any error messages displayed on screen, for example, can help you pinpoint the problem to a specific piece of hardware or software. Other symptoms of the problem you should record are physical – which lights come on, and whether they are continuous or blinking. You should create a note of any unusual sounds or beeps from the computer, and how many, if they are long or short, and if they are high or low in pitch. Often a specific pattern of beeps indicates a certain error. The documentation for your notebook computer will tell you what each error code means. All problems with notebook PCs can be grouped into one of the following categories, which you should remember while collating the symptoms of errors:  

software hardware

software If errors are encountered during the installation of a program, or application, the disks from which it is installed may be damaged, or the program may be corrupted. In this case, you should contact the software vendor, obtain another copy of the program and try to load it. If the error occurs while you are actually using the program, you should consult the documentation or online help, in the first instance. The error may be well-known and easily fixed. hardware If you don't find any problems with software, you need to check the hardware. You should try and use an initial troubleshooting checklist to eliminate simple hardware problems first, before considering more complex issues.

If the computer doesn't start properly, something may be wrong with the self-test, power sources, or power-on password. If the self-test succeeds, the computer tries to load the OS first from the A drive and then from the C drive, or vice versa, depending on how the boot priority is set. If the self-test fails, the computer may suddenly stop booting, produce several beeps and stop, produce random characters on the screen, or display an error

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message. You should then record exactly what occurred, turn off the computer, and check all connections. If the test fails again, you may have to contact your vendor.

2. Troubleshooting power supplies Power difficulties are much more common with notebook computers than with desktop PCs, because notebooks can use a number of different power supplies. If it is not plugged into a wall power supply via its AC adapter, a notebook computer draws most of its power from a battery pack. Possible power supply problems include     

AC power failure shutting down due to overheating failure of the battery to power the computer failure of the battery to charge short battery life

AC power failure Most notebook computers will have a DC IN indicator, a light which, when on, indicates that the notebook is using an AC adaptor, rather than the battery. You should locate this indicator, and, if it isn't on, check that the connections to the computer and to the power outlet are secure. You should also ensure that the power cable and the connections are in good condition, by replacing damaged cables and cleaning dirty connections with a cloth. If these actions do not solve the problem, you should contact your dealer. shutting down due to overheating Most notebooks have a mechanism whereby they shut down automatically if they overheat. This kind of behavior will be indicated in some way ( an indicator light may blink intermittently, for example ( and you should consult the manual for exact details. In these situations, you should wait for the indicator to stop, and then try to restart the notebook. A failure to restart usually indicates a more serious problem and you may need to return the unit to the manufacturer. failure of the battery to power the computer If the battery doesn't power the computer, it may be discharged, and you should connect the AC adaptor to it to recharge it. In some cases, the battery may have exceeded its recommended lifetime, and will have to be replaced. failure of the battery to charge Notebooks will have some kind of indicator light, which informs you that the battery is charging itself from the wall socket via an AC adapter. A completely discharged battery will not start charging immediately, so you should wait a few minutes for the light to turn on. If the battery is too hot or cold, you should let it reach room temperature before it can start charging properly. You should ensure the battery terminals are clean, by wiping them with an alcohol-moistened, soft cloth. If the indicator still fails to shine after 20 minutes, you may need to replace the battery. short battery life If a battery doesn't last for very long, you should fully discharge and then recharge it.

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You should also check the power consumption settings, and try using a power-saving mode, which will enable the computer to conserve power when it is switched on, but not being used.

3. Troubleshooting devices The setup configuration of a portable computer can cause keyboard problems such as  

some letter keys produce numbers garbled output to screen

some letter keys produce numbers Because notebooks do not have room for a numeric keypad, many models have a numeric keypad overlay function that enables you to use some keys as if they were number keys. You select this function by pressing a key or combination of keys. This is useful if you need to enter a large amount of numerical data. If some of the letter keys on your keyboard produce numbers on screen, you should check that this numeric keypad overlay function is not enabled. garbled output to screen In some instances, software that you run on the notebook can remap the keyboard – reassign each key to a different value. If the output on screen is not what you expect and you have eliminated other possible causes, you should check for this. Such software might be employed by people who want to use the same notebook for creating documents in two languages that use entirely different characters – Korean and English, for example.

A notebook computer can use an external monitor or a built-in liquid crystal display (LCD). Many notebooks have a shortcut key that enables you to switch between an external monitor and the LCD display. If you are not using an external monitor and you cannot see the LCD display, you should ensure that the notebook is not configured to use an external monitor by pressing the shortcut key, or configuring the appropriate settings. If you are connecting a printer to a notebook, and the printer doesn't turn on, you should check that the printer is connected to a wall outlet, and that this outlet is supplying power. If a notebook and the printer can't communicate, you should first make sure that the printer is turned on and that it is online. Then you should perform a visual inspection, and make sure that the cable connecting the printer to the computer is secure and undamaged. You should check that the appropriate port is configured, depending on whether you are using a parallel or serial printer, and ensure that the software you are using is configured so that it recognizes the printer. If your hardware seems to be functioning normally, you should check the software and printer help files. The way you troubleshoot a problem with a pointing device depends on the type of device you are using. The device may be   

serial built-in PS/2

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serial If a serial mouse does not respond, you should check that the mouse connection to the 9-pin serial port is secure. You should attach a serial mouse to the port before you turn on the computer. You should also check that your software is configured to recognize the mouse. built-in Many notebooks have a built-in pointing device, such as a trackball, touchpad, or a small joystick embedded in the center of the keyboard. If these devices do not work, you should check that you do not have an external mouse connected also. This can disable the built-in device, unless the notebook is configured to use both. PS/2 If you are using a PS/2 mouse, you should check that the mouse is firmly connected to the 6-pin port on the computer. You should turn off the computer, make sure the mouse is firmly connected, and then turn the computer back on again. You should also check that your software is configured to recognize the mouse.

4. Troubleshooting drives If a notebook computer does not boot from the hard disk drive (HDD), you should check the floppy disk drive (FDD), remove any disks (if present), and then reboot. If there isn't a floppy disk in the FDD, some of your operating system (OS) files may be missing or corrupt, and you should refer to your OS documentation. If the HDD on a notebook is running slowly, you can run the same utilities as you would on a desktop PC. So you can defragment the notebook's HDD by running ScanDisk and the Disk Defragmenter. Your OS documentation will tell you how to access these utilities. If this fails to solve the problem, you may need to reformat the disk and reload the OS. A problem with a notebook's memory modules may cause the unit to beep and to warn you to remove an incompatible memory module from a specified slot. You perform the following steps to remove an incompatible memory module:     

disconnect the AC power and peripheral devices remove the battery pack remove the memory module replace the battery or AC connection turn on the power

The form factor for CD-ROM, CD-R, CD-RW, DVD-ROM, and DVD-RW drives designed for notebook computers is the same. This means these drives experience similar problems. If you can't access a CD or a DVD, you should    

check the drive drawer ensure that the disk drawer is clean Ensure that the disk is clean check the hardware and software configuration

check the drive drawer

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You should seat a CD or DVD properly so that it lies flat in the tray, with the label facing upward. Then you should ensure that you shut the drawer properly so that it clicks into place. ensure that the disk drawer is clean You should remove any foreign objects or dirt, which may block the light from the laser that reads the CD or DVD, from the disk drawer. Ensure that the disk is clean If the disk cannot be read, the surface of the disk may be smudged or dirty. You should remove any dirt from the disk with a clean, dry cloth, which you may moisten with water if necessary. Do not use solvents to clean the surface of the disk. check the hardware and software configuration You should ensure that the correct drivers for the drive are installed. You should also check that the necessary execution lines are present in the config.sys and autoexec.bat system files.

If some CDs and DVDs run but others don't in a drive, you should check that the hardware and software configurations match and that the drive supports the type of disk you are trying to read. For example, most CD-ROM drives will read CD-R disks, but may not read a CD-RW disk. Similarly, a DVD-ROM drive may play a DVD-Video disk, but not read a DVD-RW disk. You should check that the region code on the DVD matches the region code on the drive. The following problems may occur with an external FDD:   

the drive doesn't work you can't run programs from the drive you can't access a floppy disk

the drive doesn't work If the drive doesn't work at all, there may be a faulty cable connection. You should check the connections to the computer and to the drive. you can't run programs from the drive If some programs run correctly, but not others, you should make sure that your software configuration is appropriate for the hardware you are using. you can't access a floppy disk If you can't access a floppy disk, you should try accessing another floppy disk. If other disks work correctly, the problem almost certainly lies with the disk rather than with the drive.

Docking stations and port replicators are devices that allow you quickly and conveniently to connect peripheral devices to a notebook, effectively turning it into a desktop computer. When a notebook computer is docked in such a device, all I/O devices – the internal display, keyboard, and pointing device – are usually disabled. When troubleshooting a problem at a docking station or port replicator, you should check if the notebook functions correctly independently of the docking station. You should check that the docking port that connects to the docking station or port replicator is aligned correctly.

5. Troubleshooting ports and sound systems

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Problems you may encounter when using a modem with a notebook are very similar to those encountered when you use a desktop PC. So you should check the port settings (external modems use the serial port), device conflicts, and the physical connections between the modem and the notebook. Many notebooks have a built-in, internal modem. You may encounter the following specific problems when trying to connect using a modem:  

errors due to configuration settings errors that may be resolved with AT commands

errors due to configuration settings As with desktop PCs, problems with using an internal or external modem with a notebook can result from incorrect configuration settings. So you should check the settings for the modem itself and for the application that is trying to use the modem. errors that may be resolved with AT commands If you are having trouble configuring the modem or the application using it, you have the option of using AT commands, which can be issued at a HyperTerminal interface. For example, if you cannot receive an incoming call, the problem may lie with the number of rings the modem will count before answering a call. You can change this setting within the application using the modem, or by using the ATS0 command, which disables automatic answering.

Most notebooks have one or more Personal Computer Memory Card International Association (PCMCIA) slots, which can accommodate PCMCIA cards. Other models may have a secure digital (SD) slot, which can accommodate SD cards ( a type of flash memory commonly used in devices such as a digital cameras. If problems occur with either the SD or PCMCIA cards, you should   

reseat the card in the slot check the connections between the card and any device to which it connects check the documentation that comes with the card for further information

If a universal serial bus (USB) connection problem occurs on a notebook computer, you should check that  

there is a secure connection between the USB device and the USB port on the computer. the device drivers are properly installed

If a notebook computer fails to connect to a local area network (LAN), you should check for a firm LAN connection between the network connector on the notebook and the hub, and consult a network administrator if you can't solve the problem yourself. If you are using a wireless connection to a network, you may have a problem with

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  

a wireless LAN connection a Bluetooth connection an infrared connection

a wireless LAN connection If you can't access a wireless LAN, you should check if the notebook has some mechanical setting ( such as a switch ( or software setting which must be configured to enable wireless communication. . The notebook will need a wireless network interface card (NIC), which may be a wireless PCMCIA network card. Connectivity problems may be due to the card itself, rather than the notebook or network. a Bluetooth connection If you can't access a Bluetooth device, you should check any mechanical or software settings which may enable wireless communication. Also, you should check that the device is powered, and if some type of Bluetooth management software must be running on the notebook. Some notebooks have a built-in Bluetooth function, whereas others require a Bluetooth PCMCIA card. If your notebook has the built-in functionality, it may not work with a card. an infrared connection If you have problems with an infrared connection, you should ensure that the infrared peripheral device is within the recommended maximum distance to the infrared port on the computer. The device should have a direct line of sight to the computer, so you must remove any obstructions in the path. You should also check that the infrared peripheral device is plugged in and switched on.

Almost all notebooks have a built-in sound system, with internal speakers, and integrated audio jacks and volume controls. If a problem with this system occurs, you should    

try adjusting the volume control in case it is set too low check the software which controls volume settings – the application and the operating system settings ensure that any connections ( to a set of speakers, for example ( are secure use the Device Manager to check that the sound function is enabled and that there are no device conflicts

Summary The problems encountered while using a modem with a notebook are very similar to those encountered when you are using a desktop PC. All problems with notebooks can be grouped into one of two broad categories – hardware or software. You should try to categorize any problems that occur as an aid to your troubleshooting procedures. Power difficulties are much more common with notebook computers than with desktop PCs, because notebooks can use a number of different power supplies. Most problems of this kind are related to the battery or an external power source.

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Different problems with devices such as the keyboard, pointing device, and printer that you use with a notebook computer require specific troubleshooting procedures. You can resolve some problems that affect the keyboard and pointing devices by changing the system configuration. Printer difficulties might be caused by the printer itself, rather than the setup of the notebook. If a notebook computer doesn't boot, you should check if there are any disks in the floppy disk drive (FDD) and then try a reboot. If you are having problems with the notebook's hard disk drive (HDD), you can use the same utilities as you would on a desktop PC. You follow the same procedure for CD-ROM, CD-R, CD-RW, and DVD-ROM drives – you clear the drive drawer, clean the disk, and check the drivers. You should ensure that a notebook computer works correctly before using it in a docking station. The problems encountered with using a modem with a notebook are very similar to those when you are using a desktop PC. So you should check the port settings, device conflicts, and any physical connections to the modem. Difficulties may also arise with external cards, such as Personal Computer Memory Card International Association (PCMCIA) cards, and these can be resolved in a similar fashion. You may also experience problems with network connections – the procedures for solving these depend on the kind of network to which you are connecting.

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Gathering information and troubleshooting 1. Tools for diagnosis and repair A computer technician's toolkit should contain a comprehensive range of tools for the diagnosis and repair of both hardware and software problems. Three categories of tools allow you to troubleshoot computer problems.   

Hardware tools Software tools Measurement tools

Hardware tools The hardware tools that should be in a technician's toolkit include screwdrivers, pliers, and IC extractors. At least a medium-size Phillips-head screwdriver should be in the toolkit. And at minimum, there should be two sizes of flat-head screwdriver – a small jeweler's size and a medium size. A set of Torx screwdrivers will also come in handy. Needle-nose pliers are useful for keeping small objects steady while you are working on them. Your technician's toolkit should include several pairs – at the very least, you will need one pair with a blunt nose of a stronger, sturdier type, and one pair with a sharper, tapering nose. Although most components on a modern computer are soldered to the motherboard, integrated circuit (IC) extractors – or IC pullers – are indispensable for removing ICs from their sockets. Various types of IC extractors are available. Further useful hardware tools to include in your toolkit are a flashlight, antistatic equipment such as an antistatic mat, and insulated tweezers. When selecting the tools for your toolkit, you should try to ensure that they are of a nonmagnetized type to prevent damaging magnet-sensitive computer components when you use the tools inside the computer. It's also useful to keep all hardware tools in a box designated for computer troubleshooting. Software tools The technician's toolkit should include emergency boot disks, antivirus software on disks, hardware diagnostic tools, and general-purpose utility software. An emergency boot disk enables a clean boot of a PC – even in the case of the failure of the hard disk drive (HDD). Once the computer is running, this can enable you to identify and troubleshoot the cause of a boot problem. Antivirus software on disks enables you to scan for viruses when you are troubleshooting a PC problem. Antivirus software can detect and eliminate existing viruses, as well as protect a computer system from virus attacks. Hardware diagnostic tools can assist in diagnosing a variety of hardware computer problems. An example of such a tool is a diagnostic card for identifying problems with the computer's boot process. Once installed, the card examines the boot process and reports errors in the form of number codes. You can look up an error code on a key for further details about the source of an error. General-purpose utility software can assist in the diagnosis of problems with the computer's software, assist in data recovery, monitor the performance of a computer system, and provide system security.

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If you are going to keep your software tools in the same box as your hardware tools, you should keep them in a plastic case away from any magnetized objects in the toolkit. You should also ensure that the software tools you use are those recommended for the particular hardware or software that you are troubleshooting. Measurement tools You can use a variety of electronic equipment to diagnose hardware problems. One of the most basic items that you need in your technician's toolbox is a multimeter. A multimeter is a single instrument that measures electrical current in amperes (amps), voltage in volts (V), and resistance in ohms. Computer technicians have to know what multimeter reading to expect for various components to determine whether the component being measured is faulty. For example, a good 2-amp fuse would give a resistance reading of 0 ohms, whereas a PC will give a reading close to -12 V, +12 V, -5 V, or +5 V DC. Depending on the type of speaker being tested a good speaker will give a reading of either 4 or 8 ohms. A defective speaker, for example, is likely to give a reading of 0 ohms for a short circuit or infinity for an open circuit. Computer technicians most commonly use a digital multimeter to test voltage and resistance. The output reading is given in digits on a liquid crystal display (LCD). The digital multimeter is a unit that includes the following components: an LCD a Function/Range Switch a COM Input Terminal a DC Input Terminal The Function/Range Switch is a dial that comprises different functional segments. The 12 o'clock position is the Off position. The DC voltage settings are shown to the left of the Off position, the AC voltage settings are shown to the right of it, and the resistance settings are shown at bottom left between the 6 o'clock and 9 o'clock positions. Before using a multimeter to test voltage, you must set the voltage level to the upper voltage range. This ensures that the voltage level of the device or component you're testing doesn't damage the multimeter. The initial voltage reading that a multimeter provides is an approximate reading. Once you've obtained this reading, it is good practice to reduce the multimeter's range to obtain a more accurate reading. Most voltage tests that you need to perform as a computer technician are of DC circuits. To test a DC circuit, you connect the multimeter in parallel with the component you're testing in a live circuit. This entails connecting the reference lead to a ground point and then connecting the measuring lead to the component you're testing. The multimeter reference lead and measuring lead connect to the power supply connector on an Advanced Technology (AT) or an Advanced Technology Extended (ATX) system board. In addition to using a multimeter to test voltage, you can use it to measure the resistance of components in a circuit. This is useful for testing fuses and checking cables and connectors. You always measure the resistance of a component only once you've removed it from a live circuit. It is therefore very important to remember to switch off the power before taking resistance measurements.

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2. Information gathering The three key principles that should inform your approach to gathering information for troubleshooting are   

be observant gather information verify the problem

The computer user who reports a problem is the most important source of information for troubleshooting the problem. From the user, you need to determine exactly what happened when the problem occurred to enable you to isolate the problem. This includes establishing the context in which the problem arose, the symptoms of the problem, and any details of error codes. The power-on self test (POST) is a built-in test that a PC performs automatically every time it's switched on. This test is a useful diagnostic tool for determining problems with the system's hardware. If the POST detects a problem, the basic input/output system (BIOS) can give  

a visual error message an audio response (beep code) – the meaning of which depends on the system's BIOS type and version

The BIOS indicates errors in the POST differently, depending on the system and BIOS version you're using. As a technician, you have to be able to recognize what the BIOS error means to identify and troubleshoot the problem.

3. Troubleshooting the boot process You can observe the boot process to help diagnose hardware and software problems with a system. A cold boot occurs when you first turn the power on, whereas a warm boot occurs when a PC is already on and the operating system (OS) performs a reboot. The cold-boot process can be divided into three general phases:   

the POST loading the operating system (OS) loading the graphical user interface (GUI)

A number of events make up each of these phases to complete the boot process. A particular series of events occur in a successful POST from a cold boot.

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When the power is switched on, the power supply fan activates. The keyboard lights flash as system components are reset. Then a BIOS message displays, and a memory test flickers as the POST tests system memory. If a floppy disk drive (FDD) is installed, the POST then proceeds to determine whether the system is configured to boot from the FDD. This causes the FDD access light to go on temporarily. The hard disk drive (HDD) access light then goes on temporarily, indicating that the system is accessing its boot information. Once the POST has completed, the system prepares to load the OS. The BIOS looks for additional boot information and the FDD access light comes on briefly. The BIOS then searches the hard drive for boot information and instructions. Once the system has located the boot files, the hard drive light comes on to show that it is loading and configuring the OS. An important first step you have to take when troubleshooting computer problems is to determine whether the fault lies with the hardware or if it's software-related. Observing the boot process can help you do this. If a hardware problem is detected by the POST, the system may display an error message or emit a beep code. The error message "Keyboard error", for example, indicates that the keyboard may not be connected correctly. Hardware-related problems may result because of hardware configuration errors, as well as hardware failures. Hardware configuration errors can occur when you add a new device to a system or when you use a system for the first time. These errors result if settings for a component in the CMOS and on the physical component don't all match. To check the settings in the CMOS, you use the CMOS Setup utility. Configuration error codes differ from system to system and depending on the version of the BIOS you're using. A "Press F1 to continue" message may follow an error message and allows you to enter the CMOS Setup utility to check for appropriate settings. Other BIOSs may require you to press another key – for example, the Esc key.

4. Troubleshooting FRUs If an error results from a hardware failure, you generally need to identify and replace the faulty hardware. Field replaceable units (FRUs) are hardware components that you can remove from a system and replace easily. FRUs therefore provide ready solutions when troubleshooting hardware problems. Typical FRUs are the keyboard, system board, FDD, HDD, video adapter card, and monitor. Important principles to remember when troubleshooting FRUs include

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 

ground yourself test and replace components

ground yourself Before touching any of the system board components, you ground yourself – by making contact with the exposed top of the power supply, for example. You do this to prevent electric shock that could result from any metal-oxide semiconductors on the board. test and replace components Before replacing a component, it is a good idea to test the replacement to ensure that it's functioning correctly. Exchanging a component with one you know is functioning enables you to determine whether the original component was causing the problem. It is also a way of isolating the primary source of a system problem in which multiple components fail.

Summary There are three categories of tools that should be in every technician's toolkit – hardware tools, software tools, and measurement tools. Hardware tools should include a range of screwdrivers, pliers, and IC extractors. Software tools include emergency boot disks, antivirus software on disks, hardware diagnostic tools, and general-purpose utility software. To troubleshoot a problem effectively, you need to observe it carefully, gather information, and then verify the problem. The computer user who reports a problem can be the most important source of information. The power-on self test (POST) that the PC performs at startup is a useful diagnostic tool – it indicates a hardware problem by generating a beep code or a visual error message. Errors that occur during the boot process can help you determine whether a problem lies with the system hardware or is software-related. A cold boot occurs when the system is first turned on, whereas a warm boot occurs when the OS performs the boot. In a cold boot, the boot process can be divided into three phases – the POST, loading the operating system (OS), and loading the graphical user interface (GUI). Usually, hardware problems are detected during the POST and software errors are detected once the POST has completed. Field replaceable units (FRUs) are components that you can remove and replace easily. To troubleshoot FRU problems, you should ground yourself, and exchange components to determine if they are causing problems.

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PRINTERS, MAINTENANCE and SAFETY ISSUES Printer technologies 1. Printer types and basic mechanics The printer is one of the most common output devices used with PCs today because many people still prefer to work with a hard copy of a document. Most of the printers on the market today can be divided into the following three broad categories:   

impact printers older non-impact printers newer non-impact printers

impact printers Impact printers operate by striking an inked ribbon against the paper, so transferring characters onto the page. Daisy-wheel printers and dot-matrix printers are the most common printers of this type. Impact printers print at a lower output and quality than non-impact printers, so they are not that popular today. However, they are still used in certain situations – for example, where multiple copies of the same form are required, as in some point of sale (POS) machines used for credit card transactions. older non-impact printers Older types of non-impact printers use chemically-treated or heat-sensitive paper. A thermal printer, for example, uses heat-sensitive paper that turns black when heated to print characters. A drawback of thermal printers, however, is that the copy they produce fades rapidly. newer non-impact printers Newer non-impact printers include ink-jet printers and laser printers. Ink-jet printers heat and then spray minute ink droplets onto a page to print characters. On the other hand, laser printers use electrophotographic imaging – a process that harnesses the light-sensitive properties of particular organic compounds that conduct electricity when exposed to light (a laser beam). Laser printers generally print at a higher quality and speed than ink-jet printers, but they are more expensive.

All printer types require precise mechanical mechanisms to ensure print accuracy and quality. One important mechanical consideration for dot-matrix and ink-jet printers is the requirement for a precisely positioned printhead. For most printers of this type, the printhead carriage (the component containing the printhead) moves across the page on rods that extend the width of the page. Laser printers, on the other hand, use a rotating drum that moves the paper at a precise rate.

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Another mechanical consideration is the feed mechanism – the way in which the paper moves, or is fed, through the printer. Most printers use one of the following feed mechanisms:  

friction-feed pin-feed

friction-feed A friction-feed mechanism feeds paper through the printer and holds the paper in place on the printer roller by the friction of the turning roller. This mechanism usually feeds single, separate sheets of paper to a printer and accepts a limited range of paper weights. Modern non-impact printers use a friction-feed system. pin-feed A pin-feed mechanism uses pins that hook into a row of holes on either side of a page to feed paper through a printer. A pin-feed mechanism can feed a continuous sheet to a printer because the pins hold the paper in place. The pins in a pin-feed mechanism are either a feature of the platen itself – in the case of a platen pin-feed mechanism – or are part of a motor-driven pin tractor. A platen pin-feed mechanism requires a fixed paper width, whereas a pin tractor has adjustable tractor wheels that support different paper widths. Impact printers generally use a pin-feed system.

Regardless of the printer type, characters can be created either as  

Fully formed characters Dot-matrix characters

Fully formed characters A fully formed character is printed fully formed –that is, fully filled in, or solid, with no spaces – on the page. Most modern printers produce these character types. Dot-matrix characters A dot-matrix character is divided into dots of columns and rows. By suitable placement of the dots any character can be formed. Dot-matrix printers produce these character types.

However characters are created on the page, the font of the character is important. The font describes a design for a set of characters and so determines what the characters look like on the page. Fonts can be defined, or represented, using the following common techniques:   

Bitmap Vector-based TrueType

Bitmap Each character in a bitmapped font – also called a raster-scanned font – is represented as a unique bitmap image – a pattern of dots. They are printed by displaying the bitmap image on paper. Vector-based

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A computer generates the characters in a vector-based font each time they are required by applying a mathematical formula to a stored outline of character styles and sizes. Vector-based fonts therefore require less storage space than bitmapped fonts. The appearance of a vector-based font can be quickly altered by changing the stored mathematical formula for each character. So, unlike bitmapped fonts, vector-based fonts are scalable and rotatable. TrueType TrueType is a font technology developed by Apple, but now widely used in both Macintosh and Windows operating systems. TrueType fonts – like vector-based fonts – are stored as outlines, generated from a mathematical description of the characters you want to represent. However, before the character is printed or displayed, it is converted to a bitmap by using a program known as the TrueType rasterizer. The bitmap for each TrueType character is stored in a font cache. This speeds up the printing process because the printer can retrieve the fonts directly from memory.

2. Dot-matrix printers A dot-matrix printer prints dot-matrix characters, created by the printhead. The printhead itself contains 9, 18, or 24 print wires – or pins. It is these pins that strike against the inked ribbon to create the printed character, and a greater number of print wires results in sharper dot-matrix characters, leading to a higher print quality. The key components of a dot-matrix printer are the     

Main control board Timing belt Printhead assembly Printhead positioning motor Control panel

Main control board The main control board interprets signals from a computer's printer port and communicates with the printhead positioning monitor. It also controls the paper feeder, character generators, and the printhead wires. The RAM and ROM the printer has will be located on this board. Timing belt The timing belt converts the rotation of the printhead positioning motor into the linear motion that the printhead assembly makes as it moves across the page. Printhead assembly The printhead assembly, which contains the actual printhead, moves across the print wires across the width of a page on a bar positioned in front of the platen. Printhead positioning motor The printhead positioning motor moves the printhead from side to side across the page. Control panel The control panel allows you to access various printer functions, such as to pause or cancel printing. It may also provide information on the status of the printer – online or offline, or out of paper for example.

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3. Ink-jet printers An ink-jet printer operates by ejecting small ink droplets through a nozzle and onto the paper. Ink-jet printers not only print black on white, but can also be used for color printing, through the use of different colored inks. The quality they produce approaches that of laser printers, at a lower cost. Ink-jet printers use either of the following methods to eject ink droplets through the nozzle:  

mechanical vibration thermal shock

mechanical vibration Ink-jet printers that use mechanical vibration use the vibrations of a piezoelectric material – a type of material that changes shape in response to an applied voltage – to push ink through the nozzle. thermal shock Ink-jet printers that use thermal shock heat ink within or just behind the ink-jet nozzle. This heating produces an air bubble, which forces a drop of ink out of the nozzle. When the heat is removed, the bubble collapses, and the nozzle refills.

An ink-jet printer includes the following components:    

Paper feed roller Printhead positioning motor Printhead assembly Home position sensor

Paper feed roller The paper feed roller is the component that draws, moves, and ejects the paper – using a frictionfeed mechanism – through the printer. Printhead positioning motor The printhead positioning motor is the mechanism that moves the printhead assembly back and forth in front of the platen, the roller directly behind the position where the printhead creates the characters. Printhead assembly Positioned on a bar or shaft, the printhead assembly holds the actual ink-jet cartridge. Its movement is regulated by the timing belt as it moves in front of the platen. Home position sensor The home position – or maintenance area – is the area to which the printhead moves when printing is complete. Its function is to prevent the ink in the jets from drying out.

4. Laser printers Laser printers use electro-photographic imaging to print at a high quality and at high speed. Developed by Xerox, electro-photographic imaging uses a focused laser beam, which the printer modulates and focuses onto a rotating drum.

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The drum of a laser printer is covered by a negatively charged photosensitive plastic. When the laser touches the drum, it creates positively charged areas which attract negatively-charged particles of toner. The toner is then transferred to paper as the paper moves through compression rollers. A high-temperature lamp fuses the toner to the paper. A laser printer receives character data from a computer, and converts it to a serial bit stream that the scanning laser receives. The laser printing process then consists of the following six steps:      

cleaning conditioning writing developing transferring fusing

cleaning During the cleaning process, a laser printer cleans the drum physically and electrically. A rubber cleaning blade scrapes residual toner from the drum to clean it physically. The drum must also be cleaned electrically – in other words, any residual electrical charge must be removed from the drum, so that the drum is electrically neutral. This is achieved using an erase lamp, which bombards the drum with light of a specific wavelength. After this process, the drum should be free of toner and will have a neutral charge. conditioning Once cleaned, the drum must be conditioned, or charged, to ensure that it receives new images properly. This entails charging the drum with the primary corona wire so that it holds a uniform negative charge (typically -600 V) across its entire surface. writing During the writing process, the laser beam transfers the image onto the surface of the negatively charged drum. Any point that the laser hits on the drum will become less negatively charged than the rest of the drum. Such points are said to carry a relative positive charge, and will attract toner particles. developing During the developing process, the toner is transferred to the relatively positively charged areas on the drum. The toner, held on the surface of the developing roller, is negatively charged. The magnitude of this charge is such that it will be attracted to those areas on the drum which carry a relative positive charge – those areas hit by the laser – but will be repelled from the other areas of the drum, which still carry the negative charge. transferring During the transferring process, the transfer corona charges the paper positively, causing negatively charged toner particles on the drum to move to the paper. After the image has been transferred, a static charge eliminator wakens the positive charge on the paper, so as to ensure it does not stick to the drum. fusing Up to this step, the toner is held on to the paper by an electrostatic attraction, and still has to be permanently transferred to the paper. During the fusing process, the toner particles and the paper move through two rollers. The fusing roller, containing a quartz lamp, is heated, and melts the toner particles onto the page. The other roller – the compression roller – applies pressure to the

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page. In this way, an image is permanently fixed onto the paper.

5. Specialized printing technologies Specialized printing technologies include solid ink, thermal wax, and dye sublimation printing. Solid ink printers use ink sticks made of solid wax that change phase (from solid to liquid) during the printing process. The printer liquefies the wax sticks in the printhead, jets the liquid wax onto a transfer drum, from where it is cold-fused onto the paper as it passes through the printer. It is important not to move solid ink printers once they have warmed up because the melted wax may damage them. Solid ink printers are designed to be left on, and are usually shared over a network – most models are equipped with Ethernet, parallel, and small computer system interface (SCSI) ports. Solid ink printers are used in specific circumstances – for example they may be used to quickly develop prototypes for product packaging, allowing decisions to be made before using a more expensive technology. Dye sublimation printers work by heating solid ink to such a high temperature that it sublimates, or turns directly into a gas, without becoming a liquid. The ink is held on a color transfer ribbon, often called a colored film. The printhead heats this ribbon and vaporizes the ink, which is then absorbed by specially prepared paper, and the result is a high-quality continuous tone image, comparable to a photograph. Dye sublimation printers are expensive to operate and maintain. For this reason, their use is restricted largely to specialized fields such as graphic arts, photography, and scientific research, where print quality is paramount. Thermal wax printers work in a similar fashion to dye sublimation printers in that they use colored rolls of plastic film coated with wax-based colorants. However, the image is created by melting the wax onto specialized thermal paper. Thermal wax printers print at low speed, but are ideal for specialized applications such as printing on transparencies.

Summary Printers may be grouped into three main categories – impact printers, older nonimpact printers, and newer non-impact printers. Impact printers include dotmatrix printers, older non-impact printers include thermal printers, and newer non-impact printers include ink-jet and laser printers. Printers in these categories

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all create fully formed or dot-matrix characters, using either friction-feed or pinfeed mechanisms. The font technologies they use can be bitmap, vector-based, or TrueType. Dot-matrix printers are impact printers that use a hammer to strike an inked ribbon onto a page to create dot-matrix characters. The key components of a dot-matrix printer are the main control board, the timing belt, the printhead assembly, the printhead positioning motor, and the control panel. Ink-jet printers are non-impact printers that use mechanical vibration or thermal shock to transfer jets of ink onto a printing surface. Their primary components are the paper feed roller, printhead positioning motor, timing belt, printhead assembly, and home position ink-jet sensor. Laser printers are non-impact printers that use electro-photographic imaging to produce high quality documents at high speed. The six stages in the laser printing process are cleaning, conditioning, writing, developing, transferring, and fusing. Other printer technologies include solid ink, dye sublimation, and thermal wax printers. These are suited to specialized applications and printing environments.

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Printer interfaces, options, and upgrades 1. Printer interfaces Printers can connect to networks or to standalone computer systems through different kinds of printer interfaces – or printer ports. The interface type you use should depend on the type of printer and its intended use. Many printers use the parallel port. In older PCs, parallel ports were mounted on a card. In newer PCs, the motherboard supports a parallel connection, either directly or through a dongle. Originally, parallel communication using the parallel port was hampered by a number of problems, including a lack of standards, poor bidirectional capability, and low data transfer rates. To resolve these difficulties, the Institute of Electrical Engineers (IEEE) defined a new standard – IEEE 1284 – for the parallel communication. It specifies, for example, the type of cable that can be used, and the kinds of connector attached to this cable. IEEE 1284 continued to support the standard female DB25 (25 pin) connector on the PC, and the 36 pin "Centronics" connector at the peripheral device, the printer in this case. IEEE 1284 specifies five modes of operation. Three of these are the compatibility or legacy mode, the nibble mode, and the byte mode, which are useful in certain circumstances, but the data transfer rates they can facilitate are relatively low. The two remaining modes are designed for high-speed, bidirectional data transfer. They are  

Enhanced Parallel Port (EPP) Extended Capability Port (ECP)

Enhanced Parallel Port (EPP) The standards for the Enhanced Parallel Port (EPP) mode were actually developed before IEEE 1284, but EPP was incorporated into IEEE 1284 with some minor changes. With EPP, hardware controls the handshaking process (in this context, the process by which the peripheral device and the PC initiate communication). This frees up the CPU, and also allows manufacturers to incorporate performance enhancements while adhering to the EPP standard. As a result, data transfer rates approaching 2 MBps are attainable. Extended Capability Port (ECP) The Extended Capability Port (ECP) mode was proposed by Microsoft and Hewlett-Packard and can support the highest data transfer rates of all the IEEE 1284 standards. ECP reduces the need for applications to control the data transfer process, and Microsoft have introduced a compression technique – Run Length Encoding (RLE) – which is part of their ECP standard. These capabilities significantly enhance the performance of ECP when working with scanners and printers, where large chunks of data can be efficiently compressed and transferred without the need for close supervision.

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In addition to parallel connections, printer interfaces to standalone computers include    

Serial Small Computer Systems Interface (SCSI) Wireless Universal serial bus (USB)

Serial A serial port transfers data serially, or one bit at a time, in contrast to the parallel port, which transmits 8 bits of data simultaneously. Serial ports are identified as COM ports – COM 1, for example, or COM 2 – on IBM-compatible computers. The serial port is not in common use for printers today, but was used in the past with older printers and plotters. Small Computer Systems Interface (SCSI) SCSI is a parallel interface standard used to attach peripheral devices – including printers – to a PC. It allows for faster data transfer speeds (up to 80MBps) than either serial or parallel ports. There are a number of different SCSI standards however, which can lead to incompatibility issues. Wireless Wireless technology allows devices to communicate without wire connections. This allows more flexibility in the location of a printer. Infrared Data Association (IrDA) is an example of a wireless technology standard, and require a direct line of sight and support only one-to-one communication. The IrDA receiver must be placed within 15 degrees of the line of transmission. Bluetooth is another wireless specification that allows devices within a range of ten meters to communicate. The key advantage of this technology is that Bluetooth-enabled devices can locate and communicate with each other with little or no user intervention. Universal serial bus (USB) USB is an external bus standard that supports fast data transfer rates and easy installation of peripheral devices such as printers and scanners. Most modern PCs and printers will have a USB port, and these are expected to replace both serial and parallel ports in the future.

In addition to connecting a printer to a standalone computer, you can connect it to a network. Previously, network printing was achieved by connecting the printer to a host PC, through a standard printing interface – a serial or parallel port, for example. This host PC was itself connected to the other remote computers on the network. To allow network communication, you had to enable print sharing on the host computer's operating system. Modern printers – called network-ready printers – contain an integrated network controller and an Ethernet LAN adapter so that you can connect them directly to a network. You connect other printers to a LAN via a print server port. This device can connect up to three printers to a network.

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Older printers that support networking use coaxial cable to connect directly to a LAN. Newer printers use twisted-pair Ethernet cable to connect to a network. This 10/100Base-T cable plugs into an RJ-45 jack at the back of a printer

2. Printer options and upgrades Printers need to be fast and efficient enough to handle the job flow traffic to them. You can order upgrades and options to enhance a printer's performance. You can perform some upgrades yourself, whereas other upgrades require factory installation. Upgrading the following printer components involves taking off the outer casing, installing the upgrade, and reassembling the printer:   

RAM Hard disk Network interface card (NIC)

RAM A RAM upgrade will improve a printer's performance, especially for printing large amounts of data, and extra RAM is particularly important for speeding up the printing of color graphics. You can easily increase the standard memory of a printer by adding standard inline memory modules (SIMMs). Usually though, purchasing a printer with a large memory is generally cheaper than adding extra memory later. Laser printers require a larger memory than dot-matrix or ink-jet printers, as these printers compose an entire page in memory and then print it onto paper in one pass (dot-matrix and ink-jet printers print line by line). If you are using a laser printer, and receive out-of-memory error messages when printing graphics or pages with lots of fonts, your printer probably needs more memory. Hard disk A printer hard disk supplies high-capacity storage for printer-related tasks. It can store fonts and print jobs to free up RAM and other resources. Network interface card (NIC) A NIC allows certain types of printers – like large-throughput laser printers – to connect directly to a network. This allows for data transfer to and from the printer at network speeds. Normally, you upgrade the NIC itself only if a network is upgraded.

Apart from the hardware and software requirements of a printer, there are other, physical printer components which allow you to maximize printer efficiency and customize a computing environment. Two of these are  

trays and feeders finishers

trays and feeders A printer should be able to accept at least 100 sheets in its paper tray so that you don't have constantly to restock the paper supply. Higher specification models accept up to 250 pages, and some have multiple paper trays that allow you to stock more than one type of paper. You can also

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get special trays for non-standard paper sizes, as well as envelope feeders for some laser printers. To increase a printer's paper input capacity, you can add optional paper cassette feeders. finishers Finishers speed up the organization of printed pages by performing tasks such as mass stacking, stapling, 3-hole or 4-hole punching, and job offsetting. Finishers that support a wide range of paper types and finish options are available.

By combining an imaging device, a modem, and a printer in one piece of hardware, you can perform the functions of a scanner, a printer, a copier, and a fax machine. This is significantly cheaper than buying each hardware device separately. The disadvantage of this is that copy and fax functions need user control, which can interrupt other operations you are performing using a printer. Multifunction – or "all-in-one" – machines are single devices that support scanning, printing, copying, and fax functions. The most complex function is the fax capability, so a multifunction device is really a fax machine that you can use as a printer, scanner, or modem from your computer, or leave to run on its own as a fax and copier. Advantages of multifunction machines are that they can continue to run in fax and copy mode when you turn a computer off and that fax operations don't interrupt print operations. You can also use these devices to do small copying jobs. A drawback of these multifunction machines is that they don't provide the resolution and performance of more expensive, standalone scanners or printers. Also, if a single part of the machine breaks, say the lamp of the imaging device, you may not be able to perform any other function – printing for example – until you repair that part.

Summary Types of printer interfaces include parallel, Small Computer Systems Interface (SCSI), universal serial bus (USB), network, infrared, serial, FireWire, and wireless interfaces. Many printers have a parallel port. To maximize high-speed parallel communication between the parallel printer and the PC you should set the parallel port settings on the printer to ECP and set your PC's parallel port setting in CMOS to ECP. Printers may also use coaxial cable or twisted-pair Ethernet cable to connect directly to a network. Upgrades – including adding RAM, installing a network interface card (NIC), and upgrading the hard disk – can enhance a printer's performance. Physical components such as paper trays and finishers assist in printing and organizing multiple-page print jobs. Multifunction devices, which combine the functions of a scanner, a printer, a copier, and a fax machine, are available. These cost a fraction of the total price of the individual components, but provide a lower quality.

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Troubleshooting printers 1. Troubleshooting ink-jet printers To troubleshoot any printer, you should always consult the vendor documentation that accompanies it. This documentation offers specific guidelines on printer usage and solutions to possible problems. Most printers include a self-test function that allows you to check their output for faults. If a printer prints pages without errors during a self-test, it is likely that a problem lies with the host computer, the signal cables, or the printer interface rather than with the printer itself. However, if the printer fails to print, or prints incorrectly, you need to troubleshoot the printer. When troubleshooting ink-jet printers, you are likely to encounter four common problems.    

Cartridge difficulties A stalled printhead Paper-feeding problems Failure to print

Cartridge difficulties Ink cartridges are the components that require the most attention in an ink-jet printer. If the density of a printout is faint, you can adjust the print density setting via the printing software you're using. If this fails to resolve the problem, you may need to replace or refill the ink cartridges. To replace most ink cartridges, you first move the printhead carriage assembly to the printer's center. You then remove the old cartridge by freeing it from its clips or holders and lifting it out of the printer. Problems with the nozzles of an ink-jet cartridge are often indicated by white, black or colored lines in the output. This can be caused by a defective nozzle, or nozzles, in which case the best solution is to replace the cartridge. However, the nozzles may simply be clogged, which is likely to occur if a printer isn't in regular use and the ink in the nozzles dries out. You can clean cartridge nozzles manually by removing the cartridge and either gently wiping the cartridge face with a swab or gently squeezing the ink reservoir. You should never use solvents to unblock a nozzle because they can dilute the ink, which may cause it to flow uncontrollably through the nozzle. With modern printers, you'll probably have the option to clean the cartridge nozzles automatically. For instance, with the Hewlett-Packard HP 710C series of printers, you can select the Clean the print cartridges option from the Services tabbed page of the printer's Properties dialog box. Problems with the ink cartridge usually cause streaks and lines in the print output.

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Such effects can also be due to dust or dirt in the printhead assembly. To clean the assembly, you should follow the manufacturer's guidelines. If you have to remove the print cartridge as part of this cleaning, do not leave it out of the assembly for more than 30 minutes. A stalled printhead If the printhead stalls during printing, an ink-jet printer will continue to print without moving the paper. This can result from a fault with the home position sensor, the control board, the timing belt, the power supply, or the printhead-positioning motor. To test the home position sensor on an ink-jet printer, you first disconnect the power to the printer. You then manually move the printhead carriage to the center of the printer and turn the printer back on. If the carriage moves to the home position and does not shut off or return to the center of the printer, you need to replace the home position sensor. To test the control board, you manually move the printhead carriage to the center of the printer with the power off, and turn the power back on, just as you did to test the home position sensor. If the printhead moves on startup but doesn't move during normal printing, you need to replace the control board. If the printhead carriage will not move at any time, even after you restore power after manually moving the printhead carriage with the power off, you should replace the printhead-positioning motor. Before you do this though, check that the printer is not in Maintenance mode – in which the printer keeps the printhead assembly in home position. Paper-feeding problems If paper stalls in a printer, the print output appears as a thick dark line across the page. Possible reasons why paper could stall, in other words fail to move through the printer, are a motor and gear train fault and incorrect paper thickness settings. To check for a fault with the motor and gear train, change the printer to offline mode and hold down the Form Feed button on the printer. If the paper doesn't feed, it indicates that you need to troubleshoot the motor and gear train. If the print is skewed as the paper moves through the printer, you should check if the paper thickness selector is properly set and that the paper-feed rollers aren't worn. If the thickness settings are correct but the paper still jams, you need to replace the paper-feed rollers. Failure to print If an ink-jet printer fails to print, you should check the ink supply in the cartridges. Printing may fail even if they are not completely empty. The likeliest cause of a failure of an ink-jet printer to print is that the cartridge is empty, so the first thing you should do in such a situation is to check the ink supply in the cartridges. Remember that printing may fail even if they are not completely empty. If the cartridge contains enough ink and the printhead is still not printing, you should instruct the printer to perform a self-test. If the printer will not print from the self-test, there may be a fault in the printer itself.

2. Troubleshooting dot-matrix printers The first step in troubleshooting a dot-matrix printer, as with any other printer, is to localize the source of the problem by running a self-test. If the printer runs the test successfully, the problem lies elsewhere. Five common problems affect dot-matrix printers. 

Ribbon cartridge difficulties

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   

Stalled printhead Printhead printing incorrectly or not at all Paper stalled Power supply failures

Ribbon cartridge difficulties The ribbon cartridge of a dot-matrix printer must be replaced periodically. The ribbon – which moves across the face of the platen during printing – is housed in a controlled wad inside the cartridge. A take-up wheel extracts new ribbon out of the wad during use. The printer's output becomes faint and disfigured when the ribbon becomes worn. Once this occurs, you need to replace the ribbon cartridge. Many dot-matrix printers use a snap-in ribbon cartridge. You replace this type of cartridge by first moving the printhead carriage assembly to the center of the printer. You then remove the worn cartridge by freeing it from its holders and lifting it out of the printer. You should tighten the ribbon tension of a new cartridge by turning its tension knob in a counterclockwise direction until the ribbon is stretched tight. You then snap the new cartridge in place, ensuring that the ribbon is between the printer and the ribbon mask. You can slide the assembly back and forth to check if the ribbon moves correctly. Stalled printhead If the printhead of a dot-matrix printer stalls during printing, only a single block of print appears in its output. The components that are the most likely to cause this problem include the printhead positioning motor, the home position and timing sensors and the control board. The timing belt and the power supply can also cause the printhead to stall. To troubleshoot a stalled printhead, power down the printer, and manually move the printhead to the center of the printer. Now turn the power on again. If the printhead moves to the home position and doesn't switch off or if it does not move back to the center of the printer, you should replace the home position sensor. However, if the printhead moves when the power is turned back on again, but does not move during normal printing, replace the control board. You'll need to replace the printhead positioning motor if there is no movement of the printhead at all. If print output is skewed from left to right, it could be as a result of a problem with the printer's bidirectional mode settings or a malfunctioning of the home position. Printhead printing incorrectly or not at all A dot-matrix printer may fail to print at all if the printhead is moving too far away from the paper. You should adjust the printhead's gap lever to correct this problem. If the printhead is not printing, or printing incorrectly, then the print wires of the printhead may be the cause. If these wires are not being energized, you need to check the power supply connections and, if necessary, swap the control board for one that you know is functioning properly. If the problem persists, you need to replace the printhead. In some cases, problems with the printhead may result in printing errors, rather than a complete failure to print at all. Two common symptoms of such problems are printed output that fades from left to right and printed output in which the tops of characters are missing. A solution to the problem of fading print output is to adjust the spacing between the platen and the printhead carriage rod. This allows you to obtain proper printing.

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If the tops of characters are missing in print output, it is usually because the printhead is not correctly aligned with the platen. In this case, the problem can be corrected by reseating the printhead in the printhead carriage or adjusting the carriage assembly to the proper height and angle. Printhead assemblies can become dangerously hot, so before removing a dot-matrix printhead assembly, ensure that it has sufficient time to cool. Paper stalled A line of dark blocks across a page indicates that the paper in a dot-matrix printer has stalled during printing. In situations like this, you should carry out a series of preliminary checks. Examine the paper-feed selector to ensure that it is set to the correct type of paper feed – friction, pin, or tractor. If the paper still stalls after the paper feed is correctly set and the printer is online, you need to check for a fault with the paper-handling motor and gear train. You do this by changing the printer to offline mode and pressing the printer's Form Feed button. If the paper fails to feed, while pressing the Form Feed button, you need to troubleshoot the motor and gear train. To do this, you unplug the motor cable and examine the motor windings' resistance. If motor windings are open, you need to replace the paper-feed motor. If the motor and gear train work, the problem could lie with the control board, the interface cable, the printer's configuration, or the host computer. Power supply failures The power supply is at fault if a dot-matrix printer shows no online or offline lights and will not function. To confirm that a power outlet is working, you can plug another device – for example, a lamp – into it. You should also ensure that the power cord is securely in place in the printer and wall socket and that the power switch is on. You should examine the power supply's fuses to see if they are in good condition. You replace a blown fuse with one of the same type and rating. However, a fuse doesn't usually blow unless a component has failed. So you need to investigate the cause of the blown fuse. You should check the drive mechanisms and motors in the printer for evidence of binding because an oversupply of current occurs when the motor or gear train bind but can't move. You need to replace the power-supply board if nothing is working even with everything connected and the power switched on.

3. Troubleshooting laser printers Most problems associated with dot-matrix printers and ink-jet printers also affect laser printers. It's very important to remember that laser printers present a unique set of safety hazards. In particular, you need to be careful of electrocution from the high voltage components, burns from the fusing area, and eye damage from the laser itself. Problems associated with laser printers can be categorized into three types.   

Paper jams and feeding problems Failure of the printer to start Print problems

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Paper jams and feeding problems The paper handling system of a laser printer is very complex. As a result, paper jams are a common problem. As the printer's components wear, paper jams become more frequent. Laser printers include a paper jam indication light that should alert you that a jam has occurred. Paper jams occur in three main sections of the printer – the pickup, registration, and fusing areas. Paper jams are most likely to occur in the paper pick-up area because its operation is complicated. Paper trays have an intricate set of sensors and pickup mechanisms that have to operate correctly to start paper handling. Tabs in each laser printer tray alert sensor switches that tell the control circuitry that the tray is installed and has a certain size of paper in it. A mechanical arm and photo detector senses that paper is in the tray. In addition to using the right size of paper, you need to ensure that the paper is of the correct weight. Paper that is too heavy overloads paper trays and causes paper jams. Similarly, using paper that is too thin may cause multiple pages to be pulled through the printer, resulting in paper jams. Coated paper can be dangerous because the coating can melt or catch fire due to the heat produced by the printer, particularly in the fusing area. Duplexers – for double-sided copying – and collators – for sorting pages – are additional paperhandling features that you can add to a laser printer. However, these devices can also cause paper jams when they become worn. Failure of the printer to start If a laser printer fails completely, you need to examine power supply components like the cord, outlet, and internal fuses. If the printer's fans and lights work, the problem could be with the main motor and gear train, the high-voltage corona wires, the drum assembly, or the fusing rollers. A problem with the high-voltage power supply will be accompanied by a failure of the contrast control, because this power supply ensures that toner is transferred to the drum and so onto the paper. If a laser beam is not generated – resulting in a "Missing Beam" error message, its likely that the DC section of the power supply has failed. However, faulty laser scanning modules and control boards may also cause this error.

If a laser printer is powered up, but is not printing, you need to check if it is connected to a printsharing device. If so, connect the printer directly to the host PC and then test it to determine if the connection to a print-sharing device is responsible for the problem. Its usually better to use a line printer terminal (LPT) 2 port to connect another printer to the PC. You should network the printers to the system if you want access to more than two printers. A laser printer that remains in a constant startup state is similar to a computer that fails to pass the power-on self test (POST) stage of the boot-up process. The printer starting up to an off-line condition means that there is most likely a problem between the printer and the host computer's interface. If the printer starts up to a ready state after you have disconnected the interface cable, the problem can be attributed to the host computer, interface, signal cable, or configuration. Print problems Print delivery problems that you might experience with laser printers include faint or smudged print, completely black or blank pages, random specks on pages, white lines through printed output, faulty print at regular intervals, and missing print. Faint prints can result from low toner levels, a contrast setting that is too low, or a fault in the corona area of the printer. If there is a fault in the corona area, you may need to replace either a corona wire or the mechanism that supplies power to this area. Smudged print indicates that the fusing section – fuser unit, its power supply, and fusing roller's unit – has failed. This can be due to an insufficient supply of AC power to the heating element. As

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a result, the fusing roller's temperature or pressure is not high enough for bondage between page and toner to occur. A black page indicates that the primary corona, the laser-scanning module, or the main control board is malfunctioning. If the primary corona is defective, uniform negative charge is not generated on the drum to repel the positively charged toner. To correct the problem, you need to replace the primary corona or drum assembly. If the problem persists, you need to replace the laser scanning module and the main control board. A blank page, on the other hand, indicates that no information has been given to the drum. In this case, the laser-scanning module, the control board, or the power supply is probably causing the fault. Alternatively, a corona wire may have broken or become contaminated or corroded. Specks on printed output can result from a worn cleaning pad for the fusing unit or a defective corona wire. Worn cleaning pads don't remove excess toner and the grid of faulty corona wires can't adjust the charge level on the drum. To solve the problem, you need to replace the corona assembly – by changing the toner cartridge or drum unit – and the fusing unit's cleaning pad. You should then test the printer a few times to clear any excess toner that may have accumulated in the printer. The problem of white lines through print output can be attributed to poorly distributed toner or a damaged corona wire. If the corona wires are accessible, you should examine and clean them or replace the module containing the corona wires. The toner can be evenly distributed by removing the print cartridge and gently tilting it from side to side. If faults in print occur at regular intervals, it's usually due to mechanical problems. Worn roller and transport mechanisms in the printer cause bad registration and bad print in cyclic form. This could be caused by the dimensions of cyclic components such as the drum, the developing roller in the toner cartridge, or fusing rollers. You should check these mechanical components regularly for any defects. A poorly aligned laser-scanning module, a dirty scanning mirror, low or poorly distributed toner, and a damaged drum all cause missing print.

Summary The first step in troubleshooting a printer is to determine whether a component in the printer itself is responsible for a problem. For ink-jet printers, the problems most frequently encountered include ink cartridge difficulties, the printhead stalling, the printhead not printing, and paper stalling. Problems common to dot-matrix printers are ribbon cartridge difficulties, the printhead stalling, the printhead not printing, paper stalling, and power supply difficulties. Common problems associated with laser printers include paper jams and paperfeeding problems, failure to start or to remain in the correct mode, and problems with printed output.

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Cleaning and protecting hardware 1. General preventive maintenance Preventive maintenance (PM) describes tasks – such as proper cleaning and careful handling – that you should perform to protect a PC. PM optimizes the lifetime of the components of a PC. It also increases the mean time between failures (MTBF) – the average time that you can expect PC components to function without problems. One of the most crucial PM tasks is regular cleaning. Some of the materials that are appropriate for cleaning a PC include     

antistatic spray denatured (isopropyl) alcohol glass cleaner a paintbrush soapy water and a cloth

antistatic spray After cleaning the outside surface of a computer component, it is a good idea to apply an antistatic spray to it. The spray helps to prevent the accumulation of static charges on the surface. You can make an effective antistatic solution by mixing one part household fabric softener with ten parts water. denatured (isopropyl) alcohol Denatured alcohol is useful for cleaning the inside of certain components – such as floppy head drives and disk drive read/write heads – because it dries without leaving a residue. However, you shouldn't use alcohol to clean moving parts – such as the gears in floppy drives and printers – because it may remove the necessary lubricant. To clean a component using alcohol, you apply the alcohol directly with a lint-free swab. You shouldn't use a regular cotton swab because cotton may clog up components. glass cleaner You should use glass cleaner only to clean the display screen of a cathode-ray tube (CRT) monitor. You should never use it to clean the screen of a liquid crystal display (LCD) monitor because most glass cleaners will corrode the screen. a paintbrush Small paintbrushes are useful for removing dust from the inside of cabinets. soapy water and a cloth The most common cleaning material for the exterior of a PC is soapy water and a lint-free cloth. Remember to unplug PC components before cleaning them to prevent electrical shock, particularly when you use water. And the cloth should be damp, rather than wet, to prevent water droplets from falling on or into components.

Corrosion caused by moisture and oxidation is a common problem at electrical connectors. It is important to follow proper handling procedures and never to touch connectors with your skin because moisture on your body can start corrosion. The accumulation of corrosion decreases the amount of electricity that flows through a connection.

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Methods for removing corrosion include  

rubbing off corrosion dissolving corrosion

rubbing off corrosion You can rub off any oxide buildup formed as a result of corrosion using an emery cloth, a pencil eraser, or a special solvent wipe. To prevent damage to a connector, it is important to rub towards the outer edge of the connector. Rubbing the edge may lift the foil from the PC board. You should also remove any dust or eraser particles once you've removed the corrosion. dissolving corrosion You can dissolve any corrosion on connectors using an electrical-contact cleaner spray. This spray evaporates quickly and leaves no residue. You should wipe off any excess spray with a dry, lint-free cloth.

You can prevent corrosion of socket-mounted components by reseating – removing and reinstalling – these devices. This also helps prevent the chip-creep effect – the loosening of chips in the CPU, chipset, or on adapter cards – caused by thermal changes.

Note It is important to handle metal oxide semiconductors using the proper procedures to ensure that no electrostatic discharge (ESD) occurs. Forceful handling, heat, and dust are three common causes of damage to computer hardware. To prevent damage to a system through forceful handling, technicians need to be familiar with and to follow proper handling procedures for sensitive components. Too much heat or humidity can cause early aging and failure of a computer's electronic components. Computer systems are designed to operate at room temperature, and temperatures above 85ºF may damage them. To prevent heat accumulation in a system, you should   

avoid clutter install fans protect the system from direct heat

avoid clutter It is important to keep the area around a system uncluttered so that there is always a free flow of air around it. Papers or books piled up too near the system can interrupt the free flow of air. install fans You should ensure that the fans for the power supply and microprocessor are always in proper working order. For microprocessors, the general rule is that any large integrated circuit (IC) device

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operating above 33 MHz must have a fan. It is advisable to add an extra case fan, because this will allow more air through the system. protect the system from direct heat You should protect a computer system from direct sunlight, and avoid placing portable heaters in close proximity to it.

Dust traps the heat that certain computer components create and causes these components to overheat. Most computer components produce static electrical charges that attract dust particles. The power supply and microprocessor fans that help prevent heat accumulation also draw dust into a system. The most efficient form of dust prevention is a dust-tight enclosure, but most computer systems do not have this. Uncovered expansion slot openings are a possible cause of dust accumulation in a system. Such openings also disrupt the flow of air in a system and so contribute to overheating. Smoke, like dust, accumulates on exposed surfaces of a computer system. Its residue sticks to surfaces and is especially damaging to moving parts such as the components in floppy disk drives and fan motors. To remove accumulated dust from a system, you can use a soft brush or a static-free vacuum cleaner. Whereas a normal vacuum produces static that attracts dust, a static-free vacuum cleaner has special grounding that removes the static charges it produces. You can help avoid dust accumulation by placing dust covers over system components when they are not in use.

2. Protecting hard drives and monitors The preventive maintenance of monitors involves regular cleaning, dusting, and good common sense practices. Using water or denatured alcohol and a damp, lint-free cloth is a good way to clean the outside of a monitor. Using aerosols, solvents, or commercial cleaners may damage the screen and the cabinet of a monitor. Before cleaning the monitor, it is important to disconnect the power cord. Hazardous voltage levels are present inside the monitor's case. You should therefore take off the outer covering only if you are fully skilled at working on this type of equipment. Because of the high voltage present, you should avoid when cleaning a monitor because of the high voltage that is present include the   

CRT neck CRT tube power supply board

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 

high-voltage anode signal processing board

It is good practice to dry the monitor after cleaning it with a static-free, soft, dry cloth to remove all cleaning residue. Hard disk drives require careful handling because of the sensitive components they contain. It's especially important to protect a hard disk drive during transportation to prevent the read/write heads and disk surfaces from knocking against each other. You can package a hard disk drive securely by, for example, placing it in a large box with static-free foam all around it, or by using a box-within-a-box arrangement with static-free foam as cushioning between the boxes. The case of a hard disk drive protects the platters in the drive. The drive's disks and read/write heads are stored in a vacuum within this case. You should never remove this case in open air because impurities in the air will damage the drive. If a hard disk drive malfunctions, it's possible to test its circuitry and connections. However, repairs within the airtight case must always be done by professionals and in a clean environment. To allow recovery from a possible hard disk drive failure, you should maintain  

software backups emergency repair disks

software backups It's important to ensure that copies of a system backup are stored in an easily accessible but safe place. You should also protect backups from unauthorized access. Only the system administrator should have access to backups in client/server networks, for example. emergency repair disks You should ensure that emergency repair disks for Windows operating systems (all versions after and including Windows 9x) are kept in a safe place. It's a good idea to keep these disks, as well as software backups, off site to protect them against disasters such as fire. You should also restrict access to emergency repair disks to system administrators.

Diagnostic tools such as ScanDisk, Chkdsk, Disk Defragmenter, and Backup are available with different versions of Windows. You should use these tools frequently as part of a preventive maintenance plan to help identify and fix errors in a hard disk drive. This ensures that a hard drive operates at its full potential.

3. Floppy disk drives and input devices The preventive maintenance required for input devices – the keyboard and mouse – is low. Only an occasional dusting and cleaning is needed. You need to clean a keyboard

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 

externally internally

externally Keyboards are particularly susceptible to damage caused by dust. Too much dust causes the circuitry to overheat and therefore to fail. Vacuuming is the most common way to remove dust from a keyboard. internally To clean a keyboard internally, you need to take it apart. The best way to clean the inside of a keyboard is to use a soft brush or a compressed can of air. You should also use a lint-free swab to clean between the keys.

Preventive maintenance for a trackball mouse involves cleaning the rollers inside the mouse, because these attract dirt and dust. So you need to keep a clean work area for using this type of mouse. To clean a trackball mouse, you  

flip it over, take off the cover, and then remove the ball clean the rollers with a lint-free swab

Be careful not to use sharp instruments that might damage the rollers to remove accumulated dirt. You should also avoid using erasers to clean a trackball because this may create tiny craters on the ball and so change its shape. A floppy disk drive is more exposed to the environment than a hard disk drive, and is generally handled more often. So floppy disk drives require greater preventive maintenance. Precautions that you should take when dealing with floppy disks include   

protection from magnetic fields safe storage careful handling

protection from magnetic fields You should not place disks near devices that produce magnetic fields because these fields can alter the data on the disks. Devices that produce magnetic fields include CRT monitors and televisions, as well as motored equipment such as freezers and vacuum cleaners. safe storage You should always store floppy disks in a clean, cool, and dry environment that is protected from direct sunlight. Large differences in temperature may result in a warped disk. careful handling You need to be careful when handling a floppy disk, especially when inserting it into the drive. Inserting a disk incorrectly can damage the disk's cover or even the floppy disk drive mechanism.

4. Maintaining different types of printers Printers are more mechanical than other computer components and so require more frequent preventive maintenance.

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Through normal operating functions, printers produce pollutants such as paper dust and ink droplets. The pollutants accumulate on the different mechanisms inside the printer and can cause them to deteriorate. There are three main types of printers – dot-matrix, ink-jet, and laser. The preventive maintenance methods you need to use for dot-matrix and ink-jet printers differ from the methods you use for laser printers. Two components of dot-matrix and ink-jet printers that will require preventive maintenance are  

roller surfaces the printhead face

roller surfaces When cleaning the printer's roller surfaces, you should use a damp, soft cloth. Hold the cloth on the platen and then swivel the platen a few times. You should never use detergents or household solvents on the rollers. the printhead face You should use a lint-free swab dipped in alcohol to clean the printhead face. This procedure should also loosen any paper fibers or ink, which sometimes causes the print wires to stick together.

Two components of a laser printer that may require preventive maintenance are  

the printer's interior the rollers

the printer's interior To clean the interior of a laser printer, you should first remove the toner cartridge, and then use a static-free vacuum cleaner to remove accumulated dust and excess toner. You should also vacuum the printer's ozone filter regularly. Never use a wet cloth to clean inside the laser printer because water mixes with the toner particles. the rollers Cleaning the rollers of a laser printer is a simple process – all you need to use is a damp cloth or denatured alcohol.

A preventive maintenance plan is an important and useful document to have on hand. It should include guidelines developed as solutions to specific problems that are found.

Preventive maintenance plan Preventive maintenance plan

Hard drive

Regularly

Back up hardware contents and use diagnostic tools

General internal

Occasionally Keep air vents clear, vacuum, and dust Ensure fans are working and seal uncovered slot openings

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Preventive maintenance plan

Keyboard

Occasionally Vacuum the exterior, dismantle if necessary, and clean the interior using a small brush or a can of compressed air

Trackball mouse

Occasionally Clean rollers with a lint-free swab

Monitor

Regularly

Disconnect power cord and clean exterior using water or denatured alcohol Do not touch the monitor interior

Printers

Regularly

Clean the rollers with a damp cloth or denatured alcohol For dot-matrix and ink-jet printers, use a lint-free swab dipped in alcohol to clean the printhead face For laser printers, use a static-free vacuum cleaner to remove accumulated dust and excess toner from the interior

Summary Preventive maintenance (PM) for PCs involves handling and cleaning their components correctly to prevent problems or failures from occurring. Common causes of faults with PCs include corrosion, forceful handling, dust accumulation, and heat. PM for monitors involves regular cleaning with appropriate materials. However, you should avoid contact with specific parts of a monitor because of the high voltage that they carry. Hard disk drives need protection during transportation and protection from excessive heat or humidity. To protect data in the event of hard drive failure, you should maintain system backups and emergency repair disks. Input devices such as the keyboard and a trackball mouse require occasional cleaning. You should keep floppy disk drives clean, protect floppy disks from magnetic fields, and store them in a cool, dry environment. Printers are more mechanical than other computer components and so need increased PM. Pollutants produced during normal operation can cause mechanisms to deteriorate, so regular cleaning of printers is essential.

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Maintaining the hard disk and UPS 1. The Defrag utility Hard drive maintenance is essential for ensuring the optimal functioning of a PC. The hard drive is the most important secondary storage component of a PC. A number of diagnostic tools available in all versions of Windows – the Chkdsk, ScanDisk, and Defrag utilities – assist in hard drive maintenance. The Defrag utility is a software application that discovers and then repairs the fragmentation of files on a hard drive. Fragmentation is the storage of single files across a number of clusters that are not in contiguous sectors. The operating system (OS) of a newly formatted hard drive stores the data for a file in consecutive clusters, beginning with the first available cluster. The consecutive clusters that contain data for a single file form a chain. Operating systems such as Windows 95 use the file allocation table (FAT) to keep track of the clusters in which file data resides. When files are deleted, new files can be stored in the clusters that the old files occupied. If the new files need extra clusters, however, any used clusters are skipped and the next available cluster is used. With the continuous deletion and addition of files over time, the data for individual files is fragmented. It may reside across a large number of clusters, each in a different location on the drive. Hard drive fragmentation is a disadvantage because it  

slows down file access makes recovery more complicated

slows down file access Each time a computer needs to access a file, it has to search for all the parts of that file. Fragmentation makes accessing a file slower because the OS has to retrieve its clusters from numerous locations on the drive to read it. makes recovery more complicated Files that are stored in a continuous chain are easier to recover, if corrupted, than files that are fragmented.

To ensure optimal performance, you should defragment your hard drive about every six months. You can run the Defrag utility from a command prompt or by opening it from the Windows desktop. You should close all other open applications before you use the utility. You access the Defrag utility by selecting Start - Programs - Accessories System Tools - Disk Defragmenter.

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The Defrag utility launches and allows you to select the drive you want to defragment

2. The Chkdsk and ScanDisk utilities The Chkdsk utility is a DOS-based tool that checks hard disks or floppy disks for errors, including errors associated with the FAT. You can run the Chkdsk utility from the command prompt on all versions of Windows, although it has been replaced by more sophisticated tools.. The Chkdsk utility can detect errors that are typically associated with a corrupted FAT, including  

Cross-linked clusters Lost clusters

Cross-linked clusters A cross-linked cluster is a cluster to which more than one file points. Lost clusters A lost cluster is a cluster that is recorded as a used cluster but to which no file points. This prevents the cluster from being used to store data.

You should close all other applications before using the Chkdsk utility. Many applications create temporary files while operating, and these files may interfere with the operation of the utility. It's a good idea to run Chkdsk after you have used a startup disk. The CHKDSK command supports a number of options, including 

/F, for auto correction

 

>, for redirection /V, for full path and name

/F, for auto correction The /F option finds and repairs errors on the disk – the C drive in the case of the command CHKDSK C: /F – such as lost or cross-linked clusters. >, for redirection The Chkdsk utility supports the redirection character, >, common to many DOS commands. In the command CHKDSK C:> Myfile.txt, the Chkdsk utility will run on the C drive and direct its output to the file Myfile.txt. /V, for full path and name The /V option displays the details of all paths and filenames for all files on a disk. The command CHKDSK C: /V, for example, displays this information for the C drive.

The Chkdsk utility is launched from the MS-DOS window. You type CHKDSK at the MS-DOS prompt and then press Enter. The Chkdsk utility checks the specified disk and displays information about it, including any problems it detects and details about occupied and remaining space.

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ScanDisk is a Windows utility designed to replace the Chkdsk utility. In addition to finding and repairing lost or cross-linked clusters, ScanDisk   

checks the FAT for problems associated with long filenames and the directory tree scans a disk for bad sectors if you select the thorough scan option repairs problems associated with hard drive structure if the drive was compressed using Windows DriveSpace or DoubleSpace

You can run ScanDisk from the command prompt or from the Start menu. In Windows 2000 and Windows XP, you access ScanDisk using Windows Explorer by right-clicking on the disk you want to check, selecting the Properties option, clicking the Tools tab, and clicking the Check Now button. To access ScanDisk from the Windows 98 desktop, you select Start - Programs - Accessories - System Tools - ScanDisk. The ScanDisk utility opens and allows you to select the drive you want to scan and the type of test – Standard or Thorough – that you want to perform. You can run the ScanDisk utility from the command line, using a number of options including 

/P, for information

 

the default option /N, for errors

/P, for information The /P option provides information without fixing a drive. the default option The default option provides information and repairs errors on the specified disk. /N, for errors By default, the ScanDisk utility starts and stops automatically. However, with the /N option, it will stop to report errors on the specified disk.

3. Surge suppressors and UPS The voltage transmitted via AC power lines may experience surges (spikes) or drops below the effective voltage (brownouts). Full power losses – blackouts – may also occur. Changes in voltage level can permanently damage computer equipment. To prevent this from occurring, you can regulate voltage using devices such as an uninterruptible power supply (UPS) or a surge suppressor. A UPS protects computer equipment and conditions, or regulates the power supply.

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Most UPS devices are heavy boxes that include an on/off switch and outlets for a computer and its components. You plug these devices directly into an AC outlet. A UPS can provide either a  

standby power system truly uninterruptible power system

standby power system A UPS that acts as a standby power system monitors power inflow for extremes in voltage level. If it detects a reduction in voltage, it channels its battery output into an inverter circuit. The inverter circuit switches the battery's DC output into an AC voltage resembling the commercial power supply and supplies this power to the equipment it protects. This process usually occurs within 10 milliseconds. The battery of a UPS that acts in this way is not part of the power loop and extracts only the power it needs to stay charged. Usually, these types of UPS do not provide a high level of protection against voltage fluctuations because of the output switching process they use. truly uninterruptible power system A UPS that provides a truly uninterruptible power supply continuously monitors and filters voltage fluctuations. The output of these types of UPS is continually attached to the batteries and converters, which convert DC into an AC power source resembling a stable, commercial power supply. So when the power supply is disrupted, no output switching is needed. The battery uses its own power to continue functioning. As a result, this type of UPS provides a high level of protection against fluctuating voltage levels.

The different ratings used to measure the power output of a UPS are  

volt-ampere duration of power supply

volt-ampere Because voltage and current are out of phase in an AC system, you should use the volt-ampere (VA) rating of a UPS to determine its capacity to provide a simultaneous supply of voltage (V) and current (A). The VA rating of a UPS should be higher than the VA rating of the equipment it protects. Note that the VA rating is different from the wattage rating, which is a power consumption value calculated by multiplying the voltage and current use at a specific time. duration of power supply It is essential to know the length of time a UPS will be able to supply power. Because a UPS is battery-powered, it uses an ampere-hour rating. This can be calculated by multiplying the battery's output current by a given amount of time. For example, if the battery is capable of supplying a current of 2.5 amps for an hour and a half, the amp-hour rating is 3.75.

You should keep only the important components – such as monitors, infrared devices, and system units, but not laser printers – of a system connected to a UPS. This avoids shortening the life of its battery unnecessarily. To test the capacity of a UPS, you switch off the AC power source. When you do this, an alarm should sound. If the monitor remains on once you've done this, it indicates that the UPS battery can support the system.

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A surge suppressor – sometimes called a surge protector – protects computer equipment from voltage spikes. It does this by short-circuiting the power line if it detects voltages that are too high. A surge suppressor is a relatively inexpensive device that usually consists of a small box with a few outlets, an on/off switch, and a three-wire cord. Surge suppressors require a three-wire outlet connection. Adapters that allow threewire devices to be used with two-wire outlets counteract the electrical ground connection, which can make the suppressor ineffective. A surge suppressor absorbs surges in voltage, blocks surges in voltage, or uses a combination of these strategies. A shunt type suppressor absorbs surges, whereas a series type suppressor blocks surges. When choosing a surge suppressor, you need to consider its clamping speed and its clamping voltage – the let-through voltage. Surge suppressors are available as power strips, wall-mounted units, and consoles that fit under the monitor. Surge suppressors provide limited protection against power surges. If the inside fuse of the suppressor blows, no warning is given that you have lost protection. They also are not a very reliable protection against surges caused by lightning or the startup surges that occur after a blackout. To protect a computer from power surges, you should disconnect it during electrical storms and, in the case of blackouts, until power is fully restored. When you purchase a surge suppressor, you should also check that its guarantee covers lightning damage.

Summary The Chkdsk, ScanDisk, and Defrag utilities are diagnostic tools that assist in hard drive maintenance. Fragmentation of a hard drive causes slower file access and complicates file recovery. The Defrag utility discovers and then repairs fragmentation of the hard drive. Chkdsk is an MS-DOS utility that checks the hard drive and repairs errors such as lost and cross-linked files or allocation errors. ScanDisk is another utility, designed to replace Chkdsk. ScanDisk performs the same tasks, but also checks the file allocation table (FAT) for problems associated with long filenames and the directory tree, scans a disk for bad sectors, and repairs problems associated with hard drive structure. Extreme surges and reductions in power supply can permanently damage computer equipment. To prevent this, you use uninterruptible power supplies (UPS) and surge suppressors to regulate the power supply to a PC.

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Safety and environmental measures Introduction When dealing with the computer system it is important to know the dangers that are associated with it, precautions that must be followed, and how to appropriately and safely dispose of all the components.

Electrostatic discharge (ESD) Electrostatic discharge (ESD) or static electricity is an electrical charge at rest, and can cause electromagnetic interference (EMI). Static charges of up to 25,000 volts can accumulate on the human body. This charge can easily discharge into an electrically grounded mechanism, causing irreparable damage. In fact, a charge of less than 3000 volts can damage a computer component. Although the voltages associated with static electricity are large, static electricity is not lethal to humans because the currents associated with it is usually of the order of a few millionths of an amp. Remember that it isn't the voltage that is lethal to humans, but the current that is carried with it. A low-voltage device with a high current rating, like a 100 V AC power supply, is much more lethal than high voltage with low current, like static.

Two types of damage ESD can cause the following types of damage to a computer component: 1. catastrophic failure – resulting in complete destruction of components 2. upset failure – resulting in damage to a component, which continues to function but not at its optimal capacity 3. Upset failures may occur without your detecting them, so you need to be careful about this type of failure.

Common causes of ESD Common causes of ESD are      

improperly covered cables inappropriate grounding low humidity – common in air-conditioned rooms, for example, this allows static charges to accumulate more easily the movement of machine components, such as the motors in freezers charges from people, generated through movement and clothing rubbing together poor connections

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Precautions against ESD Grounding Historically, ground referred to the actual ground, now known as earth ground. In more general terms, the term ground simply refers to the point from which you reference electrical measurements. Grounding is the process whereby you connect to the ground, whatever it may be. It eliminates any static electricity that may have built up. An important precaution is to ground yourself before touching components like the hard drive, motherboard, or memory modules. One way to ground yourself is to touch the outer case of a particular component with your finger, but for this to be effective, it is important that the power cord of the component be attached to a grounded power outlet. Also, when passing a chip to another person, you should ground yourself first, touch the other person, and only then pass on the chip. You also use grounding to protect a computer system. Grounding a system restricts EMI ( which could alter video images or damage information stored on floppy disks ( by routing generated EMI signals away from the circuitry and towards ground potential. Computer systems must always be disconnected – unplugged – from the power supply during electrical storms because it is connected to an earth ground. On the way down to earth ground, lightning might pass through the electrical path of the computer system and so cause irreparable damage. You can use static control devices to help ground yourself and a computer system. These devices include 



ground bracelets or static straps – anti-static devices that you wear on your wrist to ground yourself to the component you are working with. You attach an end to a grounded conductor – a component case or ground mat – or plug it into the ground prong of a wall outlet. ground mats – anti-static mats made from rubber or other anti-static materials that provide a grounded surface on which to work with components. Some come fitted with a cord that you plug into the ground prong of a wall outlet.

Using ground mats together with ground bracelets is one of the best ways to prevent ESD.

Static shielding bags A static shielding bag is a static control device that you use to transport and store components. A static shielding bag can be reused, and is useful as an antistatic surface on which you can place components while you work on a computer.

Anti-static spray and static-free carpeting

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Spraying or applying an anti-static solution on floors, carpets, desks, and computer components is a good way to protect against ESD. Laying static-free carpeting in the workplace can also protect against ESD.

Temperature regulation It's important to note that working on your computer immediately after coming in from the cold increases ESD potential. You can help to reduce ESD by regulating the temperature in the workplace.

Installing humidifiers Low humidity increases the potential for ESD. Therefore, in work areas where humidity is less than 50%, it is a good idea to install a humidifier.

Precautions against high voltage Two potentially hazardous areas that contain dangerously high voltages are found within the cathode-ray tube (CRT) display in a monitor and the powersupply unit. However, the hazardous areas are in self-contained units that you usually don't need to open. You should work inside the CRT case of a monitor only if you have been professionally trained to do this. Accidentally cracking this tube is extremely dangerous. Very high voltage levels can remain inside the casing even after it has been disconnected from an electrical power supply for over a year. You should discharge the high voltage of video displays before you start repairs by creating a path from the tube's anode to the case. One method is to unplug the monitor, and attach one end of an insulated jumper wire to the chassis ground of the frame. Then attach the other end to a long, flat-blade screwdriver that has a well-insulated handle. Touch only the insulated handle of the screwdriver while slipping the blade of the screwdriver under the rubber cap of the anode and make contact with its metal connection. Continuing the contact for several seconds should draw off the high-voltage charge to ground and ensure that the voltage has been fully discharged. Certain parts of the circuitry inside a power-supply unit transmit extremely high voltage levels and, more dangerously, have high current potential, so you should never open this unit.

Shock hazards Three common shock hazards are associated with metallic objects, liquids, and power cords.

Metallic objects Having jewelry or other metal-based objects near the electrical components of a computer system can be hazardous even though relatively low voltages are

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present in the system unit. A general rule is never to reach inside the unit while it's still connected to a power supply.

Liquids You should keep all food and drink away from a computer and its components because of the danger of electrical shock, as well as to protect the computer. If you use liquids to clean computer components, you need to disconnect the power first and prevent cleaning solutions from dripping into the computer. Ideally, cleaning solutions should be placed on a cloth and then used on the computer. Avoid using freon-propelled sprays because they can produce ESD.

Plugs and power cords You should never use two-prong adapters when a three-prong plug should be used. This negates the safety feature that three-prong plugs offer by removing the ground of the power cord. The three-prong plug connects the computer housing to an earth ground via the power system. This protects you from electrical shock. It also helps protect equipment from voltage surges in an electrical storm. You should check cords occasionally for damage to their insulation and replace them immediately if they are damaged. You should also place power cords out of the way, where nothing can be placed on them and nobody can trip over them.

Printers and the safety precautions Laser printers are especially hazardous because the laser light they use can damage the human eye, they include numerous high-voltage areas, and some of the components they include ( the fuser area in particular ( reach very high temperatures. The printhead of a dot-matrix printer is also a potential burn hazard because it becomes very hot during its normal functioning. As a result of these hazards, a fully stocked first-aid kit should always be available in the workplace. You should also keep C-class fire extinguishers on site ( these extinguishers are designed specifically for electrical equipment.

Safe disposal of computer components Most computer components contain materials ( such as lead, lithium, mercury, plastic, silicon, or arsenic ( that are hazardous to people and to the environment. As a result, regulations govern the disposal of certain computer components. Some manufacturers also provide guidelines on how to dispose of components safely.

Disposal guidelines

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Material Safety Data Sheets A Material Safety Data Sheet (MSDS) provides guidelines on how to handle hazardous materials, as well as procedures to follow in the event of an accident. The MSDS must accompany hazardous materials when ownership is transferred and should be kept close to where the relevant materials are stored. For each component, the MSDS contains information describing        

what the material is its hazardous contents its physical data fire and explosion information reactivity information spillage or leakage procedures health hazard information other relevant protection and precaution information

Monitors and power supply units Before disposing of monitors or power supplies, it is essential that you properly discharge the components. Even after these components are disconnected, they still contain dangerous charges. Only a properly trained technician should discharge these components. Monitor disposal may be regulated, so you should also check with local or environmental officials before disposing of monitors.

Ink cartridges For environmental reasons, it is preferable to recycle ink cartridges rather than disposing of them. However, although you can refill laser printer and ink-jet printer cartridges, refilled cartridges don't provide the same quality as new cartridges. In most cases, you can return used cartridges to the cartridge manufacturer.

Batteries It is preferable to recycle batteries rather than to dispose of them. You can either return batteries to the original dealer or manufacturer or take them to the nearest recycling center. Subtitle D dumpsites exist that can handle most hardware components safely. These dumpsites are nonhazardous, solid-waste dumpsites that have been created to meet Environmental Protection Agency (EPA) standards.

Chemical solvents and cans A used can of compressed air or the solvent xylene ( which you use to clean dotmatrix rollers ( are examples of environmentally hazardous materials that you should dispose of safely. Some communities have hazardous waste drop-off sites, which you can use for these items.

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Summary Electrostatic discharge (ESD) or static electricity is an inactive electrical charge that causes electromagnetic interference (EMI). It can cause irreparable damage to a computer and its components. It is caused by cables not being covered correctly, inappropriate grounding, low humidity, the movement of machines or people, and poor connections. Precautions against ESD include grounding, static shielding bags, anti-static spray and static free carpeting, temperature regulation, and the use of humidifiers. Potential hazards of high voltages exist in the cathode-ray tube (CRT) of a monitor and the power-supply unit of a PC, metallic objects near electrical components, liquids around electrical equipment, incorrectly used plugs, and power cords that are not in good order. Safety measures for handling printers include not exposing your eyes to the laser light in laser printers, avoiding burns from the fuser area and from the printhead in dot-matrix printers, and careful handling of high-voltage areas. Most computer components contain hazardous materials, so it is important to comply with regulations and manufacturers' guidelines for disposing of these components.

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MEMORY, MOTHERBOARDS and PROCESSORS Memory types and form factors 1. Memory types Random access memory (RAM) is the working memory of the computer. It stores data and programs that the CPU is currently processing. It is measured in bytes. All types of RAM are classified as volatile. This means that if power to a computer is disrupted, the data stored in RAM will be lost. There are two basic types of RAM:  

dynamic RAM (DRAM) static RAM (SRAM)

dynamic RAM (DRAM) DRAM needs constant refreshing to maintain data, even if the power to the chip is not interrupted. Each time you refresh DRAM, the computer must rewrite the data it contains to the chip. static RAM (SRAM) SRAM stores data as long as the power to the chip is not interrupted. There is no need to refresh SRAM, so data is not constantly rewritten to the chip.

Advanced types of DRAM include   

enhanced DRAM (EDRAM) synchronous DRAM (SDRAM) extended data out DRAM (EDO DRAM)

enhanced DRAM (EDRAM) EDRAM is the combination of DRAM and SRAM. The integration of the SRAM component into the DRAM device results in a system performance improvement of 40%. EDRAM is used in L2 cache memory. synchronous DRAM (SDRAM) SDRAM uses clock signals and internal registers to synchronize requests from memory. This increases the number of requests that the processor can perform in a given time. SDRAM devices operate in sync with the system clock. SDRAM is the most popular advanced DRAM used today and is faster than regular DRAM. extended data out DRAM (EDO DRAM)

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Extended data out (EDO) DRAM memory enables a system to access data more quickly by overlapping internal operations. EDO is an improved form of fast page-mode (FPM) DRAM, also known as hyper page-mode DRAM. Unlike FPM DRAM, however, EDO DRAM allows multiple sequential memory access.

Advanced types of SDRAM include       

double data rate SDRAM (DDR-SDRAM) enhanced DDR-SDRAM (EDDR-SDRAM) enhanced SDRAM (ESDRAM) single data rate SDRAM (SDR-SDRAM) synchronous graphics RAM (SGRAM) virtual channel memory SDRAM (VCM-SDRAM) video RAM (VRAM) and windows RAM (WRAM)

double data rate SDRAM (DDR-SDRAM) DDR-SDRAM is a form of SDR-SDRAM that transfers data on both the leading and falling edges of a clock cycle. This capability doubles the data transfer rate of memory. enhanced DDR-SDRAM (EDDR-SDRAM) EDDR-SDRAM is a form of DDR-SDRAM that uses onboard cache registers to improve performance. enhanced SDRAM (ESDRAM) ESDRAM is a form of SDRAM that uses small cache buffers to provide faster data access. This type of memory is used in L2 cache applications. single data rate SDRAM (SDR-SDRAM) SDR-SDRAM transfers data on one edge of a clock cycle. synchronous graphics RAM (SGRAM) SGRAM is designed to handle graphics operations. SGRAM is single-ported and has dual-port operations that allow two memory pages to be opened simultaneously. SGRAM is in sync with the system clock and is very fast. virtual channel memory SDRAM (VCM-SDRAM) VCM-SDRAM consists of onboard cache buffers that increase multiple access times. video RAM (VRAM) and windows RAM (WRAM) Video RAM (VRAM) and windows RAM (WRAM) are special types of DRAM used for high-speed video applications. They use a dual-port memory configuration, which means that they can receive and send data at the same time. WRAM provides faster performance than VRAM.

VRAM allows the simultaneous reading of the data it contains and writing of data to screen. The processor reads images for sending to the screen as data. Then the processor writes this data to VRAM. The data is converted into analog signals, which are then sent to the screen. While the data is written to VRAM, the processor is reading data from VRAM to refresh the content on the screen. Different types of SRAM include  

asynchronous SRAM burst-mode SRAM

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 

pipeline SRAM synchronous SRAM

asynchronous SRAM Asynchronous SRAM transfers data from memory to the microprocessor. The data is returned to the cache in one clock cycle. burst-mode SRAM Burst-mode SRAM loads many data locations, over many clock cycles, from the cache. It is faster and more expensive than pipeline SRAM. pipeline SRAM Pipeline SRAM first fetches data by using three clock cycles and then accesses the data addresses from the microprocessor. It uses fewer clock cycles than burst-mode SRAM. Pipeline SRAM is less expensive than burst-mode SRAM, but not as fast. synchronous SRAM Synchronous SRAM is in sync with the system clock and can transfer data to the microprocessor in one clock cycle.

Cache memory is memory that stores recently accessed data so that it can be accessed from memory more quickly than other data. There are three cache levels:   

L1 cache L2 cache L3 cache

L1 cache L1 cache is a microprocessor's internal cache. The L1 cache is also known as the primary cache. The original Intel Pentium had 16 KB of L1 cache. L2 cache An L2 cache is a static memory cache stored on the motherboard of older Pentium processors. It is also referred to as an external cache because it is not part of the CPU. From the advent of the Pentium Pro processor, L2 cache came in the same package with the processor. However, it wasn't integrated onto the processor like L1 cache. L2 cache can be 256 KB, 512 KB, or 1 MB in size. L3 cache An L3 cache is used in Xeon and Itanium microprocessors, which are used as servers. Where there is L2 cache in the microprocessor housing and additional cache is on the motherboard then the additional cache on the motherboard is known as L3 cache.

There are two design factors that relate to the configuration of RAM – data error detection and refreshing. Data error detection is a system for identifying single-bit errors in stored data. Refreshing involves rewriting data to the chip. DRAM devices refresh data to stop the data from disappearing. The reading and writing cycles of the system perform refreshes.

2. Calculating parity

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Parity checking is the most common form of data error detection that can only detect single-bit errors. It checks for errors either in transmitted data or in the data stored in RAM. A parity checking system adds one bit – either 0 or 1 – to each word in memory, resulting in every word having either an even or an odd number of ones. A parity error occurs if a parity bit in a single memory bit changes. When a parity error occurs, the system generates a Non-Maskable Interrupt (NMI) signal. It then displays a parity error message and either displays a short memory count and then freezes or gives you the option to continue or shut down. To operate, parity checking needs additional memory. Parity can be set to   

even parity odd parity no parity

even parity Even parity involves adding either a 0-bit or a 1-bit to every group of bits to make the total number of 1 bits equal an even number. odd parity Odd parity involves adding either a 0-bit or a 1-bit to every group of bits to make the total number of 1 bits equal an odd number. no parity The majority of computers sold today use non-parity memory chips. These chips do not provide any type of built-in error checking, but instead rely on the memory controller for error detection.

To set the byte string 11010100 to even parity, for example, the system adds a 0-bit to the string. The string is then left with four 1-bits. In the case of odd parity, it adds a 1-bit to the string – resulting in five 1-bits. Error correction code (ECC) is code that detects and corrects single-bit errors but can only detect multiple-bit errors. ECC also adds an additional bit, called an error correction code bit to a byte. If ECC detects a multiple-bit error, a "parity error" message occurs and the system halts.

3. The different form factors of RAM Form factor refers to the shape and size of a device. A form factor is usually used to describe a circuit board. The following common form factors determine the size and pin configuration of memory on a system motherboard: 

dual inline memory module (DIMM)

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   

Rambus inline memory module (RIMM) single inline memory module (SIMM) micro dual inline memory module (MicroDIMM) small outline DIMM (SODIMM)

dual inline memory module (DIMM) DIMMs are a series of DRAM modules – or chips. DIMMs install upright on the motherboard. DIMMs include 168 pins and have a 64-bot data path. DIMMs are the most commonly used form factor. Rambus inline memory module (RIMM) RIMMs use RDRAM modules – or chips. These chips connect to each other in series on the motherboard. RIMMs use a loop system to transfer data and are unidirectional. RIMMs look similar to DIMMs but include 184 pins. RIMMs transfer data in 16-bit chunks and are synchronized to the microprocessor's memory bus and not the motherboard clock. This internal 16-bit data bus works in combination with a 400 MHz clock cycle. The increased transfer speed that this type of module allows results in more heat being produced. So RIMMs also include aluminum heat shields called heat spreaders that protect the chips from overheating. single inline memory module (SIMM) SIMMs install at a slight angle into sockets on the motherboard. SIMMs, like DIMMs, consist of a group of DRAM chips connected on a circuit board. Unlike DIMMs, however, SIMMs include only one signal pin. SIMM modules are available in two sizes – 30-pin and 72-pin SIMMs. SIMMs are generally available in 30-pin / 8 bits with an optional 1 bit for parity or 72-pin / 32 bits with an optional 4 bits for parity. micro dual inline memory module (MicroDIMM) MicroDIMMs are available only in one size – a 144-pin MicroDIMM that is usually found in subnotebook computers. MicroDIMMs have a 64-bit data path. small outline DIMM (SODIMM) A SODIMM is a small type of DIMM module used in notebook computers. SODIMMS are available in three sizes – a 72-pin SODIMM, a 144-pin SODIMM, and a 200-pin SODIMM. The 72-pin and 144-pin SODIMMs are the most commonly used. A 72-pin SODIMM has 32-bit data path and a 144-pin SODIMM has a 64-bit data path.

The memory bus has developed from 8 to 16 to 32 and finally to 64 bits wide. Matching the type of SIMM to the data bus size of the microprocessor is very important. Therefore, if you are working with a 32-bit microprocessor, you need to have a bank of four 30-pin, 8-bit SIMMs or one 72-pin, 32-bit SIMM. With the advent of the 64-bit wide data bus, the SIMMs' data bus size limitation is apparent – two 32-bit SIMMs are required in a paired memory bank. The development of the 64-bit DIMM prevents the need for this. You connect memory modules to a motherboard using RAM slots. There are specific RAM slots for DIMMs, RIMMs, SIMMs, and SODIMMs.

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To highlight the differences between DIMMs and SIMMs, consider the differences between the following examples.  

168-pin DIMM 72-pin SIMM

168-pin DIMM A 168-pin DIMM is an inch longer than a 72-pin SIMM. It has two notches on the bottom of the printed circuit board (PCB) and installs vertically into the socket of the motherboard. A 168-pin DIMM has pins on opposite sides of its circuit board. These pins are not electrically connected, and so form two separate electrical contacts. A 168-pin DIMM has a 64-bit wide path. 72-pin SIMM A 72-pin SIMM is shorter than a 168-pin DIMM. It has one notch in the middle of the PCB, and installs at a slight angle into the socket of the motherboard. A 72-pin SIMM has pins on the opposite sides of its circuit board. These pins are connected to form an electrical contact. A 72-pin SIMM has a 32-bit wide data path.

RIMMs use a loop system to transfer data. In a looped system, the data in one RIMM module moves forward from chip to chip. When the data reaches the last chip, on the RIMM module, it shifts down the line to another RIMM module. In this module, data also moves forward from one chip to the next, in the same direction. The data can move in the same direction while downstream data is still being sent.

4. Memory on the motherboard When you want to fit the memory bank on the motherboard, you have to use the correct number of memory modules – DIMMs, RIMMS, and SIMMs – with the correct amount of memory. DIMMs, RIMMs, and SIMMs are installed in a certain number of groups or banks, depending on the size of DIMM, RIMM, or SIMM used. And the DIMMs, RIMMs, and SIMMs in each group must be of the same size and type. You should avoid mixing memory speeds on the motherboard. For example, if you use a SIMM in one bank and a SIMM in another bank that has a slower speed, both SIMMs will work only at the slower speed. Installing memory that is faster than that of the motherboard or mixing memory speeds can cause errors in the computer's operating system. It may also prevent the computer from starting, and the computer will report less memory than you've installed. You install the following types of SIMMs differently.

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 

30-pin SIMMs 72-pin SIMMs

30-pin SIMMs You install 30-pin SIMMs in groups – or banks – of four. All SIMMs in the same group must match in size and type. 72-pin SIMMs You install 72-pin SIMMs in groups – or banks – of two. All SIMMs in the same bank must be of the same size and type.

Unlike SIMMs, DIMMs install as a single module rather than as groups. They can be either single-sided or double-sided. Single-sided DIMMs have DRAM chips on one side of the module, and are available in sizes of 8, 16, 32, 64, and 128 MB. Double-sided DIMMs have DRAM chips on both sides of the module, and are available in sizes of 32 MB, 64 MB, 256 MB, 512 MB, 1GB, and 2 GB. Motherboard documentation lists the possible DIMM capacities. You determine the total memory available on a motherboard by adding the memory size of each socket. Some motherboards have a three-slot DIMM layout. This is known as a splitbank arrangement. Slot 1 forms one bank, and slots 2 and 3 combine to form a second bank. RIMM slots are filled with RIMMs or continuity RIMMs (C-RIMMs). You use CRIMMs to fill slots that do not have RIMM modules because there cannot be any empty RIMM slots on a motherboard. C-RIMMs do not have any memory chips. 184-pin RIMMs are available with built-in ECC support and without ECC support. The density of a RIMM is the amount of data that each RDRAM chip on the RIMM can hold. Non-ECC RIMMs are available with densities of 128 MB and 256 MB. The corresponding ECC versions have densities of 144 MB and 288 MB respectively. Each RDRAM chip on a 128 MB RIMM holds 16 MB of RAM. Each RDRAM chip on a 256 MB RIMM holds 32 MB of RAM. To calculate the RIMM size, you multiply the amount of memory that each chip holds by the number of chips on the RIMM. For example, if a 128 MB RIMM has four chips and each chip holds16 MB of RAM, the RIMM size is 64 MB. A 256 MB RIMM that has four chips, each holding 32 MB of RAM, has a size of 128 MB. You install RIMMs on a motherboard in groups – or banks – of four. There must be two RIMMs in the first bank of the motherboard. And there can be two RIMMs or two C-RIMMs in the second bank of the motherboard. Each bank must contain RIMMs of the same size, and all RIMMs in a bank must

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have the same density. But the RIMMs in one bank can differ in size and density from the RIMMs in another bank. The RIMMs in all banks must run at the same speed.

Summary There are two basic types of RAM – dynamic RAM (DRAM) and static RAM (SRAM). Types of DRAM include enhanced DRAM (EDRAM) and synchronous DRAM (SDRAM), and there are different types of SDRAM. Types of static RAM include asynchronous SRAM, burst-mode SRAM, pipeline SRAM, and synchronous SRAM. Design considerations associated with RAM include the differing needs of different RAM types to refresh data and the use of data error detection. Parity checking and error correction code (ECC) are commonly used methods for data error correction. Parity checking can detect single-bit errors, whereas ECC can detect multiple-bit errors only. Memory that allows a computer to process faster can be categorized into five form factors – dual inline memory modules (DIMMs), micro dual inline memory modules (MicroDIMMs), Rambus inline memory modules (RIMMs), single inline memory modules (SIMMs), and small outline dual inline memory modules (SODIMMs). DIMMs and SIMMs use DRAM chips, and RIMMs use RDRAM chips. DIMMs are the most commonly used form factor. When you install memory modules on a system, you need to install the correct number of memory modules with the right amount of memory to fit the memory banks on the motherboard. Mixing memory speeds or installing memory that is faster than the motherboard can cause system errors.

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Configurations and settings 1. The CMOS Setup utility Complementary metal-oxide semiconductor (CMOS) RAM stores the configuration information for the system's hardware. CMOS RAM maintains this information even when the computer is switched off. The parameters stored in the CMOS can be produced automatically or manually. You access the CMOS Setup utility through the power-on self test (POST), which you access by pressing a designated key or series of keys. The main menu of the CMOS Setup utility generally includes the following configuration options:      

Standard CMOS Setup BIOS Features Setup Chipset Features Setup Power Management Setup PnP/PCI Configuration Integrated Peripherals

Standard CMOS Setup The Standard CMOS Setup option allows you to set the date and time of the system, disk drive parameters, and which types of errors will cause the system to freeze during the power-on self test (POST). BIOS Features Setup The BIOS Setup option allows you to enable or disable cache memory and shadow RAM features. It also provides boot-up options. Chipset Features Setup The Chipset Setup option allows you to configure memory – particularly DRAM and SRAM – settings to optimize the chipset. Power Management Setup The Power Management Setup option allows you to select one of three power-saving modes – Doze, Standby, or Suspend. PnP/PCI Configuration The PnP/PCI Configuration option allows you to configure Plug and Play (PnP) settings, which determine the type of hardware device installed in the system and allocate system resources to this device. Integrated Peripherals The Integrated Peripherals option allows you to configure and enable peripheral features such as the floppy disk controller (FDC) and Integrated Drive Electronics (IDE) controllers.

In addition to allowing you to access other system settings, the Standard CMOS Setup screen allows you to configure

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 

the date and time disk drive parameters

You use the date and time function, called the real-time clock (RTC), to set and keep track of the system's calendar and clock. To change the date or time settings, you first select the date and time option using the Up or Down arrow keys. Then you change the settings using the Page Up or Page Down keys. System boards include a battery that allows them to retain the date and configuration settings when a system is turned off. Older system boards contain a rechargeable nickel cadmium (NiCAD) battery for this purpose, whereas newer system boards include either a disc battery or a non-volatile random access memory (NVRAM or NOVRAM) device. The barrel style battery is used in older system boards. Newer systems that do not combine the battery and RTC units use a disc battery. Systems that combine the battery and the RTC unit into a single element use the NVRAM device. If the time on a PC is incorrect, you need to reset it. The easiest way to do this is through the operating system. If the system still fails to keep the correct time, you should check that corrosion has not collected on the battery contacts. If it has, clean the battery contacts with a pencil eraser and retry the battery. If the problem persists, replace the battery. If the system clock is still incorrect after you've replaced the battery, try replacing the RTC unit. If the problem persists, the electronic circuitry that recharges the battery could be faulty. If this is the case, you may need to replace the motherboard. You use the Standard CMOS setup screen to view and configure details of the floppy disk and IDE devices on a system. All BIOS versions have a list of hard drive types that they can support. Newer BIOS versions have an Auto Detect option that automatically detects the devices – CD-ROM drives and small computer system interface (SCSI) drives, for example – installed in a system. You can select a translation mode for a drive. However, changing the translation mode for an existing drive could result in the loss of data. Each drive type has the following translation modes:    

Auto Large Large Block Addressing (LBA) Normal

Auto In Auto mode, the BIOS will try to determine the best operating mode for a selected drive. Large

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You use Large mode with large drives that do not support LBA, and that have more than 1024 cylinders or 528 MB. Large Block Addressing (LBA) You use LBA mode with large drives that support it. This mode considers physical block addresses instead of head addresses. Normal In Normal mode, the BIOS supports a maximum of 1024 cylinders.

Base memory – or conventional memory – is the section of memory that is available to standard DOS programs. DOS systems have a memory size of 1 MB. Of this memory, 384 KB is upper memory, and the remaining 640 KB is called base memory. Extended memory – or expanded memory – is the memory found above the standard 1 MB of main memory supported by DOS systems. Extended memory is not configured in any particular way and is unavailable to most DOS programs. However, MS-Windows and OS/2 use extended memory.

2. BIOS, chipset, and power management The BIOS features setup screen – also referred to as the Advanced CMOS setup screen – of the CMOS Setup utility provides settings for     

boot-up options Level 1 (L1) cache error checking rate setting and delay virus detection

The most commonly used options on the BIOS features setup screen include      

Virus warning Boot Sequence Boot Up Floppy Seek Boot Up Numlock Status Boot Up System Speed Memory Parity Check

Virus warning You should enable the Virus Warning function during and after system boot-up. It checks for viruses that might modify the boot sector or partition table of the hard disk drive. You should generally disable the Virus Warning function when performing an upgrade to the operating system. Boot Sequence The Boot Sequence option allows you to determine which drive the computer searches first for the disk operating system. It can boot from the A: drive, the C: drive, from a CD-ROM, or from an SCSI.

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If the system cannot boot to the C: drive, the A: drive or the CD-ROM drive is enabled by default. To change the boot sequence in a system, you first select the Boot Sequence option using the Up or Down arrow keys. Then you choose the appropriate option using the Page Up or Page Down keys. Boot Up Floppy Seek When the Boot Up Floppy Seek option is enabled the BIOS tests (seeks) floppy drives to determine whether they have 40 or 80 tracks. Only 360 KB floppy drives have 40 tracks. Drives with 720 KB, 1.2 MB, and 1.44 MB capacity have 80 tracks. You can set this option to Disabled to save time during the boot-up process. Boot Up Numlock Status The Boot Up Numlock Status option has two options – On and Off. The On option puts a numeric keypad in Num Lock mode at boot-up. The Off option puts a numeric keypad in arrow key mode at boot-up. Boot Up System Speed The Boot Up System Speed option has two options – High and Low. You select the High option to boot at the default speed. You select the Low option to boot at the AT bus speed. Memory Parity Check In the Memory Parity Check option, the Enabled option adds a parity check to the boot-up memory tests. If the BIOS detects a parity error, a message appears describing the problem and, if possible, the location of the problem. The boot process stops and you must then replace the faulty DRAM. The Disabled option omits the parity check.

You use the Shadow feature to copy different system firmware routines into high memory. The BIOS Features Setup screen includes the following shadow options:       

Video BIOS Shadow C8000-CBFFF Shadow CC000-CFFF Shadow D0000-D3FFF Shadow D4000-D7FFF Shadow D8000-DBFFF Shadow DC000-DFFFF Shadow

You can enable or disable each of these options for individual portions of memory only. Suppose that your computer currently boots from the A: drive. You now want it to boot from the CD-ROM, so you need to change the boot sequence. You press the Page Up key to change the boot sequence to C, CDROM, A on the BIOS features setup screen. You use the Chipset features setup screen to set up the contents of the chipset. These contents contain a wait-state timing function for asynchronous SRAM read and writes, extended data out (EDO) reads, and page-mode RAM reads.

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The Power management setup screen allows the user to choose from the following power-saving modes:   

The Doze mode The Standby mode The Suspend mode

The Doze mode The Doze mode is a power-saving mode that decreases the speed of operations on a processor to either a quarter or a half of the normal processor speed. The Standby mode The Standby mode deactivates the hard drive and video for a certain period, before the screen blanks. To use the system again, you can press any key. The Suspend mode The Suspend mode causes everything, except the processor, in a system to shut down.

3. PnP, PCI, and peripherals settings The PnP/PCI configuration screen contains settings for a Plug and Play (PnP) standard and a Peripheral Component Interconnect (PCI) bus. It also consists of a number of slots for the system's interrupt requests (IRQs), and a number of IRQs for Industry Standard Architecture (ISA) interrupts. PnP technology allows a system to determine the type of hardware devices installed. It then allocates system resources to the devices, and configures and manages them. The PCI bus provides a rapid data path between the CPU and other peripherals.

Note To obtain the full benefits of the PnP BIOS, the operating system must be PnP-compatible. Most client operating systems, such as Windows 9x, Windows 2000, and Windows XP are PnP-compatible. During the initialization phase of the startup process, a PnP device communicates with the BIOS. The PnP device informs the system of its type, of its location in the system, and of the resources it requires. This information is stored on the device in the form of firmware. The BIOS stores the PnP information in the Extended System Configuration Data (ESCD) area in CMOS RAM. Whenever the system is restarted, both the BIOS and the operating system access the ESCD area to check if any of the PnP information has changed. This process allows the BIOS and the operating system to work together. If the BIOS detects that none of the information in the ESCD area has changed, it skips that section of the boot process.

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If the PnP operating system detects any changes, it records these changes in the hardware section of its registry. In some instances, the system's PnP logic is unable to determine all of its resource needs, resulting in a configuration error. In these cases, you have to solve the configuration problem manually. Information that the BIOS and the operating system provide can help you determine the system's resource needs. You can access the information that the BIOS stores about system resource allocations on the PnP/PCI configuration screen of the CMOS Setup utility The Integrated peripherals screen of the CMOS Setup utility allows you to enable or disable the settings for IDE drive connections, the onboard I/O functions, and parallel port operations. The Integrated peripherals screen allows you to set  

IDE functions the IDE HDD Block mode function

IDE functions The programmed input/output (PIO) field allows you to select one of five PIO modes (0 – 4) for any IDE device. The hard drive buffer stores all reads and writes on a first in, first out (FIFO) basis. The IDE FIFO modes include IDE Primary Master FIFO, IDE Primary Slave FIFO, IDE Secondary Master FIFO, and IDE Secondary Slave FIFO. The IDE Primary Master FIFO option is enabled by default, and the remaining options are disabled. the IDE HDD Block mode function The IDE HDD Block mode setting is also known as the Large Block Transfer, Multiple Command, and Multiple-Sector Read/Write mode. To allow a drive to support partitions larger than 528 MB, the IDE HDD Block mode setting supports LBA disk drive operations. You should enable this option for most new hard drives.

The programmed input/output (PIO) mode determines the speed at which data will be transferred between the hard drive and the system. Basically, the higher the mode, the faster the transfer rate. All four PIO modes are set to Auto by default. Onboard I/O functions that you can configure on the Integrated peripherals screen include settings for   

the Floppy Disk Controller (FDC) parallel ports UART 1 and UART 2 controllers

the Floppy Disk Controller (FDC)

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The FDC controller option is enabled by default. This option allows the floppy drive to boot from the onboard floppy disk controller. You disable the FDC option if you have an add-in floppy disk controller, or if the PC has no floppy drive. parallel ports The Parallel Port mode has three settings – extended capabilities port (ECP), extended parallel port (EPP), and Normal. The ECP mode is a fast, buffered, bidirectional operation. The EPP is an extended bidirectional operation. Normal mode, also referred to as the standard port, allows data to flow only in one direction. The Parallel Port mode is set to Normal by default, unless the driver software and port hardware support either the EPP or ECP modes. UART 1 and UART 2 controllers The Integrated peripherals screen displays details for two universal asynchronous receivertransmitters (UARTs) – UART 1 and UART 2. These controllers receive and transmit data through serial ports. The UARTs can be changed to support half-duplex and full-duplex transmission modes, allowing wireless communication over short distances. Both UARTs are set to Auto by default.

The ECP and EPP parallel port modes have advantages and special requirements. The ECP mode uses a direct memory access (DMA) channel to increase data throughput. When you select ECP mode, the functions of the pins of the interface are redefined. In EPP mode, a port allows data to flow in both directions, allowing increased speed. Because they operate in a bidirectional manner, both the ECP and EPP modes need a cable that complies with Institute of Electrical and Electronics Engineers (IEEE-1284). You cannot use a standard parallel printer cable with ECP or EPP devices.

Summary The main menu of the complementary metal-oxide semiconductor (CMOS) Setup utility allows you to access configuration settings that relate to standard CMOS setup, basic input/output system (BIOS) features, chipset features, integrated peripherals, Plug and Play (PnP), Peripheral Components Interconnect (PCI) setup, and power management. You use the main CMOS Setup screen to set the date and time, to set disk drive parameters, and to halt the system in the case of errors. The BIOS Setup – or Advanced CMOS Setup – screen of the CMOS Setup utility allows you to configure boot-up options, internal and external cache memory, memory parity checks, and shadowing. The Chipset Features Setup screen allows you to configure memory, particularly dynamic RAM (DRAM) and static RAM (SRAM). The Power Management Setup screen allows you to choose one of three power-saving modes – Doze, Standby, or Suspend.

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The PnP/PCI Setup screen contains settings for a PnP standard and a PCI bus, and controls the settings for the PCI slots of the motherboard. The Integrated Peripherals Setup screen allows you to set parameters for a number of IDE functions, an integrated drive electronics hard disk drive (IDE HDD) Block mode function, onboard I/O functions, and parallel port operations.

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Motherboard types and components 1. Motherboard types, connectors, and ports The motherboard – or system board – is the main component of a PC system. Different types of motherboards have different form factors. In this context, the term form factor is used to describe the physical characteristics of a motherboard, such as its size and shape. It also describes the way in which its I/O connections are positioned, and its case and power-supply compatibility. There are two main types of motherboards found in PCs today, which comply with two distinct types of form factor.  

AT (Advanced Technology) form factor ATX (Advanced Technology Extended) form factor

AT (Advanced Technology) form factor The AT form factor – sometimes called full AT – is the predecessor to the ATX form factor and is used on older motherboards. The original AT board, measuring 12 by 13 inches, was based on the ISA (Industry Standard Architecture) board for the IBM PC-AT. The AT board was followed by a smaller version called the Baby AT – measuring 8.7 by 13 inches – which matched that of the original PC-XT board. Many variations of the AT-style board have since been developed. The physical layout of an AT board also depends upon the chipset used. Older, pre-Pentium computers used a Multi I/O (MI/O) adapter card to provide AT compatible connections, whereas Pentium chipsets have integrated these I/O functions into the board itself. The AT motherboard has the following components, ordered clockwise: a keyboard connection serial ports COM1 and COM2 a parallel port, PRT1 a floppy disk drive connection two hard disk drive connections memory slots a ZIF (zero insertion force) socket for the processor expansion slots

The COM1 connector on the motherboard is connected by a ribbon cable to a DB-9M connector on one of the slot covers. COM1 is at RS-232C serial port and is usually used for a mouse. COM2 is the second logical serial port. The motherboard's COM2 connector is connected to a DB25F connector on an expansion slot cover. The parallel port features a DB-25F connector on an expansion slot cover. It is connected to the

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motherboard at the 26-pin pin block PRT1. FD1 is the floppy disk drive connector, which is connected to floppy drives via a 34-pin ribbon cable. ID1 is the port for the primary IDE channel. It is connected to an IDE device – usually the hard drive for this channel – using the special 40-pin IDE cable. ID2 is the IDE port for the secondary IDE channel. The special 40-pin IDE cable connects this port to a secondary IDE device, such as a CD-ROM drive. The expansion slot connections come in different sizes and configurations, and are located close together on the motherboard. The smallest expansion slot is the 120-pin connection peripheral component interconnect (PCI) bus. The longer expansion slots are organized in two or more groups of pins, and can be recognized by their length and divisions. ATX (Advanced Technology Extended) form factor ATX is the most widely used form factor today. It evolved from the Baby AT, and represents an improvement on this factor in many ways – for example, it has greater support for I/O devices and processor technology. The standard ATX board measures 12 by 9.6 inches – smaller than full AT, but larger than Baby AT. However, a revised specification – mini-ATX – allows for smaller boards, at 11.2 by 8.2 inches. The ATX configuration is that of a Baby AT rotated by 90 degrees, resulting in major differences in the relative positions of the CPU and the expansion slots. With ATX, the CPU sits beside the expansion slots, rather than in front of them, which makes it much easier to use full-length expansion cards. An ATX motherboard includes connections for floppy and hard disk drives, and serial and parallel ports. The ATX motherboard has the following connections, ordered clockwise around the board: expansion slots I/O ports – serial, parallel, universal serial bus (USB), keyboard, and mouse – in a vertical stack a processor socket memory slots floppy and hard disk drive connections The keyboard connector is a 6-pin mini DIN (PS/2) connector. On ATX-style motherboards, the I/O ports are usually located at the rear for easy access. On ATX boards, the power connection socket is a one-piece 20-pin slot known as the P1 connector, rather than the separate P8/P9 cabling associated with older boards. This arrangement adds a +3.3V DC supply to the usual ±12 V and ±5 V supplies. The ATX power-connector also allows for a software-activated power switch, which means that the operating system can control the PS-ON and 5V Standby (5 VSB) signals to shut down the system automatically. Another significant difference between AT and ATX boards is the cooling system. With ATX, the power supply fan blows air into, rather than out of, the case. The power supply also has a vent, positioned in such a way that it blows air directly onto the processor and expansion cards. These features reduce the need for additional fans and specialized cooling components.

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When you work on, or replace, a motherboard, you'll need to consider the form factor of the motherboard, and whether it is compatible with other system components. Remember that the openings in the case for expansion slots and port connections must be compatible with the motherboard. The standard PC, PC-XT, and Baby AT boards have the same mounting hole patterns, so they can be interchanged. But the ATX mounting hole patterns do not exactly match those of the Baby AT. The keyboard connectors also vary between boards. Systems based on AT architecture use the 5-pin DIN connector for keyboards, whereas ATX systems use the 6-pin mini DIN (PS/2) connector. RJ-11 jacks are also sometimes used. The power supply is a major consideration when dealing with compatibility issues because there are important differences between the supply for AT and ATX form factors. You can't use ATX and AT-style power supplies interchangeably for the following reasons:   

the AT power supply can't be properly secured and grounded in an ATX case because the bolt patterns are different the single connector from an ATX power supply won't fit the AT motherboard's dual (P8/P9) power connector the ATX fan blows air into the case from behind, whereas the AT power supply pulls air into the case from the front

2. USB, SCSI, and IEEE 1394 There are a number of different standards available today that enable communication between I/O devices and the computer, via a peripheral bus.   

Universal serial bus (USB) Small Computer System Interface (SCSI) IEEE 1394 (FireWire, i.Link)

Universal serial bus (USB) USB is a peripheral bus that supports data transfer rates of up to 480 Mbps. Any USB system consists of a single USB host and one or more USB devices, which are either hubs or nodes. The USB host contains the interface that provides the USB host controller. The controller itself combines USB hardware, software, and firmware. You can plug up to 127 USB devices together. Recently manufactured motherboards have built-in USB ports. ATX motherboards usually have a pair of USB connectors, and you can attach more USB devices to a system by adding PCI cardmounted USB ports. These host ports act as the system's root hub.

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Older AT-style boards supply a USB port as part of a pin connection. This is converted to a standard connector by an extra cable set that mounts in a vacant back panel slot. The USB port's operation is controlled by the CMOS settings. You usually need to access the PnP/PCI configuration screen in the CMOS Setup utility, enable USB, and assign IRQ channels to ports. You should free up IRQs if no USB device is being used. You do this by setting the IRQ allocation to "NA". USB devices that operate at 480 Mbps (USB Version 2, or Hi-Speed USB) are rated as full-speed devices, whereas devices that operate at 12 Mbps (USB Version 1, or Basic USB) are low-speed devices. Small Computer System Interface (SCSI) There are various different SCSI standards, which means that there is no industry-accepted standard for SCSI host adapters (adapter cards) on desktop PCs. This is not ideal, as most desktop motherboards need a SCSI host adapter in an expansion slot to support SCSI devices. SCSI adapter cards are available for use with Industry Standard Architecture (ISA), Extended Industry Standard Architecture (EISA), and PCI bus slots. A built-in SCSI host on the motherboard is usually connected through a 50-pin connector. You establish support for a built-in SCSI host through the CMOS Setup utility in the system BIOS. However, add-on SCSI adapter cards have a BIOS extension on the card. SCSI is fast, but can be difficult to configure – it is expected that SCSI will be replaced by IEEE 1394 in the years to come. IEEE 1394 (FireWire, i.Link) IEEE 1394 is the official name for a group of peripheral bus standards, similar to USB, that support very fast data speeds, up to 1.2 Gbps. Products that support this standard are marketed under different names. Apple uses the term FireWire (this name is often used for the standard itself), other companies use the terms i.Link (Sony) and Lynx (Texas Instruments). At the moment, only new, high-end motherboards have FireWire ports, but they are expected to become as standard as USB ports are now. While USB replaces slower serial and parallel ports, FireWire is expected to replace SCSI, especially for high-volume multimedia transmission from devices like digital cameras and DVDs. In a similar way to USB, FireWire devices can be daisy-chained and managed by a single host controller. With FireWire though, one host controller can support up to 63 devices. Another similarity is that FireWire devices are hot swappable (they can be configured or removed without a reboot). Of course, the operating system used by the PC must support the IEEE 1394 standard. Windows XP, Windows 2000, and Windows 98 support this standard, but Windows 95 and Windows NT don't. Four wires are used in all IEEE 1394 cable, which consists of two pairs of shielded twisted pair (STP) wires, enclosed in a protective jacket, in a similar fashion to network cables. However, two different kinds of cable connectors – namely 4-pin and 6-pin – are used for FireWire ports. The cable that uses the 4-pin connection just has the wires required for data, and has no pins for voltage or ground. So devices using this type of connection do require an AC adapter. The cable that uses the 6-pin connection provides the four wires required for IEEE 1394, plus two extra wires for voltage and ground. As a result, the cable itself is thicker, but devices using it do

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not need a separate power supply. A new version of the IEEE 1394 standard – 1394.3 – allows for peer-to-peer communication, so that FireWire enabled devices can communicate with similar devices without using the computer's CPU. Another feature of this standard is isochronous data transfer – continuous data transfer without interruptions. Sophisticated features such as peer-to-peer communication and isochronous data transfer mean that IEEE 1394 is well suited for devices that transmit real-time data. For example, the digital camcorder can write data in real time to a FireWire enabled disk, via the digital VCR, without the involvement of the CPU. This data may then be written to the regular hard disk of the PC. There are a number of different IEEE 1394 standards, which are compatible with each other. The IEEE1394a standard supports data speeds of 100, 200, and 400 Mbps and cable lengths up to 4.5m (15 feet). An updated version, IEEE 1394b, approved by the IEEE in 2002, supports data speeds up to 3.2Gbps and a maximum cable length of 100m (328 feet).

3. Drive connections Pentium motherboards moved the hard and floppy disk drive connections, as well as I/O port connections, onto the motherboard. Pentium-based motherboards provide the IDE host adapter and floppy disk drive controller interface connections. The floppy disk controller part of a chipset can control two floppy disk drives. The cable connects to the motherboard at the 34-pin connection.. You should take care to line up pin 1 of the connector to the signal cable's indicator stripe, which is usually a colored stripe, red in this case, along an edge of the ribbon. In some cases, the connector on the cable is notched, so it cannot be inserted another way. The IDE host adapter can control up to four hard drives, CD-ROMs, or other EIDE devices. Two IDE channels are provided – the primary IDE1 channel and the secondary channel, IDE2. Each channel can handle one master and one slave device. Hard drives and CD-ROM drives are connected to the motherboard at IDE1 or IDE2 using 40-conductor ribbon cables. You line up the connections to the hard disk drives in the same way as the floppy disk drives. The cables used with EIDE devices include Ultra ATA/66 and the similar Ultra ATA/100. They can transfer data at speeds of up to 66.6 Mbps and 100 Mbps respectively. These newer cables provide increased data throughput by doubling the number of conductors to 80. The connectors are compatible with original 40-pin IDE connection, but each pin has its own ground. Both Ultra ATA versions are backwards compatible, so the older 40-pin/40conductor ATA cable can be used with Ultra ATA/66 and Ultra ATA/100 devices.

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However, the data speed over this older cable is still fixed at a maximum of 33.3 Mbps. Each drive on each IDE channel can be either a master or a slave, which is important when considering how drive letters are allocated. The order of drive letter assignment – beginning with C – for primary partitions is IDE1 master, IDE1 slave, IDE2 master, IDE2 slave. After this, drive letters are assigned to additional partitions in the same order. So, for example, the primary partition of the master drive attached to IDE1 will be designated as C. Another partition on this drive will be assigned the letter E: if a second drive is attached to IDE1 as a slave (and if no additional drives are connected through IDE2). After you install EIDE hardware, you may configure it in the system's CMOS Setup utility. However, most modern systems have an auto-detect feature in the BIOS that can automatically configure hard drives. Sometimes, the physical layout of the drive may differ from the logical configuration that the controller relays to the CMOS. In this case, the IDE controller acts as the interface between the systems drive parameters and the drive's actual physical layout. In the CMOS setup, you can configure the IDE channels manually, and you can enable or disable both channels and set them to Auto-Detect mode or Manual Detect mode. EIDE devices can communicate with RAM using two protocols – Programmable Input/Output (PIO) modes or the more recent (and popular) Direct Memory Access (DMA) modes. Different modes offer different performance capabilities. The PIO modes for any EIDE device can be manually set in CMOS, although most PCs can set this automatically, which is the preferred option. Most EIDE devices can operate in PIO mode 3 or 4 – data may be transferred to memory at 11.1 or 16.6 Mbps respectively. To use these modes, the IDE port must be attached to the PCI bus. Some motherboards, though, connect IDE1 to the PCI-bus and IDE2 to the ISA bus. In such cases, devices on IDE2 can operate only in PIO mode 2 (8.3 Mbps). Newer EIDE devices ignore PIO modes and use DMA modes instead

Summary The term form factor is used to refer to the physical characteristics of a motherboard, and there are two main types – older AT and the newer ATX factors. Differences between them include the actual size, the level of support for

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I/O devices, and the power supplies for each board. Different communications standards require different I/O ports, which can be either built in to the motherboard or added through an adapter card. Three common I/O ports available on modern PCs are universal serial bus (USB), IEEE 1394 (also known as FireWire or i.Link), and small computer systems interface (SCSI). USB ports allow for fast serial data transmission – up to 480 Mbps – and are, in most cases, built in to ATX motherboards. IEEE 1394 uses isochronous data transfer and attains a speed of 1.2 Gbps. SCSI ports are used for fast, high-volume data transfer, but can be difficult to configure. Hard and floppy disk drive controller interface connections are found on the Pentium motherboard. Two floppy disks can be attached to the 34-pin floppy disk controller (FDC) part of the chipset. Two hard disks can be attached to each of the two 40-pin Integrated Drive Electronics (IDE) channel. Typically, the primary channel IDE1 is used for the hard disk and the secondary channel IDE2 for a CD-ROM. Various parameters relating to these channels can be set through CMOS.

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Processor sockets and CPU chips 1. Early Pentium processors The most important component on a system board is the microprocessor, as it provides the logic which allows the entire computer system to function. So it's important that you are able to maintain, upgrade, and install microprocessors, allowing you to obtain the best possible performance from the system.

Note For PCs, the terms microprocessor and central processing unit (CPU) are used interchangeably. IBM used the Intel 8088 microprocessor and its supporting chipset as the CPU in the first PCs. This is the reason why most IBM-compatible PCs still use the Intel 8088/86, 80286, 80386, and 80486, or Pentium 80586 and 80686 processors. The original Pentium processor was a 32/64 bit chip in a ceramic pin grid array (CPGA) package. Its registers and floating-point sections were the same as the 80486. It had a 64bit data bus to do Quad Word data transfers and two 8 KB caches – one for instructions and one for data. Initially, the Pentium architecture developed over the following three stages:   

First generation Second generation Third generation

First generation The first generation Pentium was named the P5. It came in a 273-pin PGA package and operated at 60/66 MHz. The P5 consumed a lot of power and generated a lot of heat because it was powered by a single +5V DC power supply. In fact, so much heat was generated that an additional fan, sitting on top of the CPU, was required. Second generation The second generation Pentium – P54C – came in a 296-pin staggered pin grid array (SPGA) arrangement, in versions that operated at 75, 90, 100, 120, 133, 150, or 166 MHz. Because of the SPGA packaging, they were not compatible with first generation boards. The P54C used less power and operated faster than the P5 because it used a +3.3V power supply. This generation of processors employed internal clock multipliers to increase the processor's performance. These multipliers allowed the processor to run at some multiple of the clock speed, although the system bus runs at the same speed as the clock signal.

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A P54C Pentium with a 50 MHz external clock that uses a 3x clock multiplier, for example, runs internally at 150 MHz. Third generation The P55C – also known as the Pentium MMX (Multimedia Extension) – is the third generation of Pentium processors. It uses 296-pin staggered pin grid array (SPGA) packaging. The packaging conforms to Intel's 321-pin Socket-7 specification. The P55C versions operate at 166, 180, 200, or 233 MHz and use a supply voltage lower than +3.3V.

2. Modern Pentium processors Intel continued to develop its line of processors, adding new features and functionality to produce chips such as the Pentium Pro, Pentium MMX (the third generation of the original Pentium), Pentium II, Pentium III, and the Pentium 4.     

Pentium Pro (1995) Pentium MMX (1996) Pentium II (1997) Pentium III (1999) Pentium 4 (2000)

Pentium Pro (1995) The Pentium Pro, introduced in 1995, was optimized for 32-bit software, although it can run software written for previous Pentium processors too. A new configuration was adopted for the Pentium Pro, which had a size of 2.46 by 2.66 inches, with a 387-pin plastic pin grid array (PPGA) case. It fitted into a special socket, called Socket 8, which no other CPU used, so the Pentium Pro was not pin-compatible with previous Pentium processors. A new feature of this chip was that the 16 KB L1 cache in the core is supplemented by an onboard 256 or 512 KB L2 cache. This L2 cache stores the most frequently used data not found in the processor's internal L1 cache. It is as close as possible to the processor core without being on the same integrated circuit (IC). The processor and cache unit are connected via a high bandwidth bus, known as the backside bus or cache bus, which allows communication at 1.2 Gbps. A gold-plated, copper, or tungsten heat spreader covers the Pentium Pro chip, which was designed for use either in typical, single processor machines, or with multiprocessor systems, such as high-volume file servers and workstations. Dual processor boards were designed with two Pentium Pro sockets to operate with either one or two Pentium Pro processors. Logic circuitry in the core of these systems manages the two processors' requests for 64-bit bus and memory access. Pentium MMX (1996) The Pentium MMX processor, also known as the P55C, was the third generation of the Classic Pentium. It added 57 multimedia-specific instructions to the original instruction set.. For this chip, the onboard L1 cache size was increased to 32 KB, divided into two 16 KB caches – one for instructions and one for data. The L2 cache is usually 256 KB or 512 KB, with a 66 MHz system bus. Different versions of the Pentium MMX run at 166, 200, or 233 MHz. It used a 321-pin staggered pin grid array (SPGA), Socket-7 arrangement..

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The MMX Pentium processor needs two separate supply voltages – one for the processor core and the other to power the I/O pins. Pentium II (1997) The next major CPU produced by Intel was the Pentium II. It included the multimedia features of the MMX processor, as well as the 512 KB L2 cache and dynamic execution of the Pentium Pro. The instruction set was refined, and the L1 cache size increased to 32 KB. The major change introduced with the Pentium II was the way in which it was packaged in a new single-edge contact (SEC) cartridge. The SEC itself requires a fan and a fan heat sink (FHS) module, both of which are shown here. A power connector on the motherboard supplies power to the fan. This cartridge fitted into a slot on the motherboard, rather than a socket, and Intel's proprietary 242-contact design is known as the Slot 1 specification. It was designed to allow the processor to operate at bus speed of more than 300 MHz. The motherboard requires a universal retention mechanism (URM) to hold the SEC cartridge in place. In most cases, you can unfold a pair of URM arms – on either side of Slot 1 – into which the cartridge is placed. Another cartridge called the single-edged processor package (SEPP) is also used with Slot 1 design in the Pentium II processor. In the SEPP housing, the processor is accessible from the back, instead of being completely covered by plastic housing as in the SEC. A pair of URM arms can also be used to hold the SEPP. A SEC or SEPP cartridge contains the Pentium II processor core, a tag RAM, and an L2 burst SRAM, mounted on a substrate.. The tag RAM is an area in the L2 cache, which tracks data stored in the cache memory. Pentium III (1999) The Pentium III is a Slot 1-compatible processor design based on the Pentium II core. The size of the L2 cache in the original processor was increased to 512 KB and the processor speed increased to 600 MHz, including a 100 MHz front-side bus speed. The Celeron is a less expensive version of the Pentium III, with a 66 MHz bus speed and 128 KB of L2 cache. Early versions of the Celeron processor employed a SEPP design. Later, versions of PIII and Celeron fitted the Intel Socket 370 specification, which marked a return to a 370-pin zero insertion force (ZIF) socket, with a staggered pin grid array (SPGA) design. The first Socket 370-pin grid array versions of the Pentium III and Celeron were plastic pin grid array (PPGA) designs, which were later upgraded in the flip chip pin grid array (FC-PGA) design. The PPGA 370 specification was the standard adopted for first PGA versions of the Pentium III and Celeron processors. With this standard, the maximum processor speed is 533 MHz, with a bus speed of 66 MHz. The PPGA specification was intended for moderate-performance Pentium systems, which are comparatively inexpensive. The FC-PGA 370 specification is an upgrade on the basic Socket 370 specification. For FC-PGA 370, Intel made modifications to the wiring of the socket, and a heat sink may be attached to the microprocessor die. This specification also used a new 0.18-micron IC technology, which enabled faster processor speeds – up to 1.26 GHz – and front-side bus speeds – 100 MHZ and 133 MHZ. The processors built using this technology were called Coppermine processors, and had 256 KB of L2 cache. Another version, Coppermine 128, had 128 KB of L2 cache.

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Another version of the PIII is the Pentium Xeon, which is available as three different types, with 512 KB, 1 MB, and 2 MB of L2 cache. The Xeon chip also uses a new Slot 2 specification, which extends the 242-contact Slot 1 arrangement to a 330-contact design. These chips are aimed at the needs of high-end servers. Pentium 4 (2000) The first Pentium 4 processors were released in 2000, and they represented a significant advance in chip design – the Pentium 4 is not based on the previous, Pentium Pro architecture, but instead uses IA-32 NetBurst architecture based on 0.18-micron technology (later versions used a 0.13 micron process). The first Pentium 4 version – also called the Willamette 423 – uses a modified Socket 370 plastic pin grid array (PPGA) design with 423 pins. It also had a Socket 478 version, and runs at up to 1.3 GHz. The later version – Northwood – produced using the 0.13-micron technology, had a larger L2 cache size (512 KB) and was available only as a Socket 478. Differences in design between the Pentium 4 and its predecessors include its instruction set, L1 and L2 cache sizes, its system bus, and the operating voltage it requires. The Pentium 4 features 144 new Single Instruction Multiple Data (SIMD) instructions, formerly called the WPNI (Willamette Processor New Instructions), but now known as Streaming SIMD Extensions 2, sometimes abbreviated as SSE-II. SIMD technology allows a single instruction to operate on more than one data set at the same time. Intel reduced the size of the L1 data cache in Pentium 4 chips to 8 KB, so as to achieve a very low latency (the time it takes memory to respond to CPU requests). However, the processor also includes a 12 KB Execution Trace Cache. The L2 cache is 256 KB or 512 KB, and can handle transfers every clock cycle. Recent Pentium 4 versions even include a 2 MB L3 Cache, designed specifically for power users, such as high-end gamers. The system bus for Pentium 4 processors can run at 400 MHz, 533 MHz, or 800 MHz, enabling very high data transfer rates into and out of the processor. The Pentium 4 core uses an operating voltage ranging from 1.7 V to 1.525 V. The case includes a metal cap to allow it to dissipate the heat that the processor generates. To ensure proper cooling, there must be good contact between the processor case and the heat sink built into the motherboard.

3. Cloned processors As successive generations of 80x86 and Pentium processors were produced, Intel faced stiff competition from other manufacturers who developed CPUs that were compatible with the Intel processors. These CPUs are known as Intel or Pentium clones. One of the main reasons Intel stopped using the 80x86 terminology, and started using trade names such as Pentium (or Celeron, or Xeon), is that a trade name may be copyrighted, whereas a number, 486 for example, cannot. In this way, Intel could distinguish its CPUs from those of its competitors, who, in time, began to use their own trade names for the Pentium clones they were producing. Two prominent manufacturers of Pentium clones are Advanced Micro Devices and Cyrix.  

Advanced Micro Devices (AMD) Cyrix

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Advanced Micro Devices (AMD) AMD manufactures several clone microprocessors. Among these are the X5, K5, K6, K6PLUS-3D, and K7. The X5 is compatible with the older DX4 processor. Its performance is comparable to that of the Pentium and MMX processors. The K5 is compatible with the Pentium. It is also Socket-7 compatible and, with small adjustments, can be used in Pentium and MMX motherboard designs. The K6 is compatible with the Pentium MMX and, like the K5, is Socket-7 compatible. Its 64 KB L1 cache is double the size of the internal cache of the Pentium II. The K6PLUS-3D has comparable performance and operation to the Pentium Pro, but it is not pin-out compatible with other processors. The Athlon is a Pentium III clone, the first versions of which used an SEC package called Slot A, which is mechanically but not pin compatible with Intel's Slot 1. An Athlon will fit into Slot 1, but not work. Athlon versions that use Slot-A cartridges include the K7 and K75 processors, which have a 128 KB L1 cache, a 512 KB L2 cache, and a 100 MHz system bus. Later Athlon versions used a ceramic PGA (CPGA) package, which needed a proprietary 462-pin ZIF socket – Socket A – which is incompatible with Intel's Socket 370. Processors using Socket A design include the Athlon "Thunderbird" and MP. Cyrix Cyrix, like AMD, produces clones of the Pentium line. One of these is the Socket 370-compatible Celeron clone processor called the Cyrix III – originally codenamed the "Joshua". The Cyrix III can be used in boards designed for the Pentium Celeron. However, the BIOS for the Celeron motherboard needs upgrading to work with the Cyrix clock multipliers. A newer version of the Cyrix processor – the Samuel processor– runs at 533 MHz and has a fast 133 MHz front-side bus. It has a 128 KB L1 cache, but no L2 cache.

4. Socket specifications and clock speeds The slot or socket is the physical connection between the motherboard and the CPU. There are different slot and socket specifications for different CPUs. One of the key differences between the various slots and sockets is in the voltage they can supply to the CPU. Starting with the Pentium MMX, Intel used a dual-voltage supply for the IC and the processor core. Older units used +5/+5 V, and newer units use +3.3/+3.3 V, +3.3/+2.8 V, or +3.3/+1.8 V. Common clone processor voltages are +5 V, +3.3 V, +2.5 V, and +2.2 V. Regulator circuits on the motherboard usually generate the different voltage levels required for clone processors. You should consult the user's guide for a system board, before upgrading the microprocessor, to check which voltages it can supply.

Socket and slot specifications Industry socket and slot specifications Number

Microprocessors

Voltage

Pins

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Industry socket and slot specifications Number

Microprocessors

Voltage

Pins

Socket 1

80486 SX/DXx, DX4 OverDrive

5

169 PGA

Socket 2

80486 SX/DXx, Pentium OverDrive

5

238 PGA

Socket 3

80486 SX/DXx, Pentium OverDrive

5 / 3.3

237 PGA

Socket 4

Classic Pentium 60/66, and corresponding OverDrive processors

5

273 PGA

Socket 5

Classic Pentium 75-133, and corresponding OverDrive processors

3.3

320 SPGA

Socket 6

Never used

3.3

235 PGA

Socket 7

Pentium 75-200, Pentium MMX, and Pentium OverDrive

VRM (2.5 -3.6 321 SPGA )

Socket 8

Pentium Pro

VRM (2.2 -3.5 387 SPGA )

Slot 1

Celeron, Pentium II, Pentium III

VRM (1.5 -2.5 242 ) SECC/SEPP

Slot 2

Pentium II Xeon, Pentium III Xeon

VRM (1.5 -2.5 330 SECC-2 )

Super Socket 7

AMD K6-2, K6-2+, K6-III, K6-III+

VRM (2.0 -3.5 321 SPGA )

Socket 370

Cyrix III, Celeron, Pentium III

VRM (1.1 V2.5 V)

370 SPGA

Slot A

AMD Athlon

VRM (1.2 V2.2 V)

242 Slot A

Socket A

AMD Athlon, Duron

VRM (1.2 V2.2 V)

462 SPGA

Socket 423

Pentium 4

1.7 V and 1.75 V

423 SPGA

Socket 478

Pentium 4

VRM (1.5 V1.65 V)

478 mPGA

Some of the socket and slot designs developed to accommodate different CPUs include     

Sockets 1, 2, 3 Sockets 4, 5, 6 Socket 7, Super socket 7, 8 Slot 1, Slot 2 Slot A, Socket A

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 

Socket 370 Socket 423, 478

Sockets 1, 2, 3 The Socket 1, 2, and 3 specifications were created for earlier generations of pre-Pentium chips. They could also accommodate Pentium OverDrive processors, that is Pentium processors specially designed to operate with these sockets, which are found on legacy boards. Sockets 4, 5, 6 The Socket 4 and 5 specifications accommodate the Classic Pentium 60/66 and the Classic Pentium 75-133 respectively. They also could accommodate the corresponding Pentium Overdrive processors. The operating voltages for these CPUs were 5V (Pentium 60/66) and 3.3V (Pentium 75-133). Socket 6 was never implemented. Socket 7, Super socket 7, 8 The Socket-7 specification allows for a voltage-regulator module (VRM) that enables different power settings to be realized through the socket. The fastest Classic Pentiums use this specification. The Socket-7 SPGA packaging is compatible with the Socket 5 PGA that the first generation Pentium processors use. Socket-7 was upgraded to Super Socket 7, which adds a support signal for Accelerated Graphics Port (AGP) slots and a 100 MHz front-side bus. The AMD K6-2, K6-2+, and K6-III processors, as well as the Intel Pentium Pro and MMX, are designed to use Super Socket 7. Socket 8 is specific to Pentium Pro. Slot 1, Slot 2 As we have seen, the proprietary Slot 1 specification was developed by Intel for the Pentium II, but the Celeron and Pentium III processors also use it. This specification allows variable core voltages, between 2.8 V and 3.3 V. A combination of Socket 8 and Slot 1 called the slotket processor is available. This design allows daughterboards containing the Pentium Pro, which uses Socket 8, to be plugged into Slot 1. The Slot 2 specification extends Slot 1 to a 330-contact SECC-2 cartridge for the Intel Xeon processor. Slot A, Socket A The AMD version of Slot 1 is Slot A, which serves the same purpose as Slot 1. Slot A is not pin compatible with Slot 1but it is mechanically compatible. AMD then followed Intel's lead in moving away from slots and back to sockets to produce the Socket A specification – a 462-pin ZIF socket for the PGA versions of the Athlon and Duron processors. No other processors fit this specification, and it is supported only by two chipsets. Socket 370 Socket 370 was a new Intel ZIF socket that marked Intel's return to the socket design, as opposed to the Slot 1 or Slot 2. It's for the Celeron processor and comes in two versions – PPGA and FCPGA. Both the PPGA and the FC-PGA versions will plug into the 370 socket, but they may require boards designed either for the PPGA or FC-PGA specifications. The FC-PGA version is design for flip chips – a CPU for which a heat sink can be directly attached to the processor die. Examples of such "flip chips" include the Cyrix III, Celeron, and Pentium III processors. Socket 423, 478

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Sockets 423 and 478 are 423-pin and 478-pin ZIF PGAs, with provision for VRM. Socket 478 features the dense micro PGA (mPGA) pin design. Both of these sockets were designed for the Pentium 4.

As CPUs became faster, a problem arose in that CPUs could now run much faster than the system bus. The bus speed is governed by the clock frequency of a crystal or oscillator. To overcome this problem, Intel developed the concept of clock doubling – the CPU core ran at one (higher) speed, whereas a second, lower speed was used for the system bus.

Note Although the concept was originally referred to as clock doubling, the CPU core may operate at any multiple of the external clock frequency. The circuitry that establishes the relationship between the speeds of the CPU and the system bus is called the internal clock multiplier, or simply the multiplier. In older systems, the CPU speed and the system bus speed were configured externally, using jumper settings on the motherboard. More recently, the Socket7 specification allows you to configure the motherboard for different microprocessors with varying CPU core speeds. Different clock speeds and multipliers have been used at the following stages of development of the Pentium processor:    

before the Pentium II Pentium II Pentium III P4

before the Pentium II All Pentium processors before the Pentium II used 50 MHz, 60 MHz, or 66 MHz external clock frequencies, which generated their internal frequencies. The value of the clock speed and multiplier was controlled by external hardware settings – jumpers – on the motherboard. So for example, you could set a clock speed of 66 MHz and a multiplier of 3 for a Pentium 200 MHz processor. Pentium II Pentium II processors use a 100 MHz external clock.. As with most modern processors, the multiplier and system bus speeds for the Pentium II can be set using the CMOS setup. Pentium III Pentium III processors, with internal speeds of up to 1.2 GHz, use a 100 MHz clock and front side bus, just like the Pentium II. However, the PIII Coppermine increased the external clock speed to 133 MHz. The Celeron, on the other hand, retained a 66 MHz external clock and bus speed until its 800 MHz version. P4 Pentium 4 processors use external clocks with speeds up to 400 MHz. They have four different memory buses for different memory types.

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You can set the clock speeds for the memory and front side buses separately. These buses work with different types of RDRAM at speeds of 400 MHz, 600 MHz, or 800 MHz.

5. CPU configuration Motherboards are designed so they can support many different processor types and speeds. The settings for the CPU itself may be established using the CMOS setup, or even by using jumper settings on the motherboard. In newer systems, the Plug and Play (PnP) process may be able to configure the processor automatically during startup, preventing damage being caused to the processor through incorrect configuration. Some important CPU settings that you may need to configure include    

bus frequency core voltage core-to-bus speed ratio CPU type

bus frequency The system bus frequency setting will make the processor run too fast or too slow if it is incorrectly configured. People sometimes increase this setting above the optimal value so as to increase the speed of older systems. If the new setting is within 20% of the optimal setting, a system may work, but this will shorten the processor's life. Greater variations might cause random lockups in the system. core voltage The core voltage setting controls the voltage level at which the microprocessor core operates. The operating voltage is a factor in speed and power dissipation. The processor won't operate if the setting is more than 20% below the recommended value, whereas a higher voltage setting could cause physical damage. core-to-bus speed ratio A mismatch of the core and bus speed can decrease system performance. Some users deliberately set the CPU clock speed to a higher value than that recommended by the manufacturer – a practice known as overclocking. Overclocking immediately voids any guarantees or warranty associated with the processor, and can cause permanent damage to it. CPU type The CPU type setting tells the system the type of CPU installed. If the setting is incorrect, the system will assume the processor in use is the one specified. The system power-on self test (POST) might identify the processor incorrectly and still run – but not well. Otherwise, the processor might lock up during POST or not run at all. This could cause damage to the processor.

If you use automatic CPU configuration, you should ensure that the BIOS version supports the parameters of the microprocessor. If you upgrade the microprocessor and the BIOS does not support the new one,

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any number of configuration errors may occur. For example, if you install a 1 GHz processor in a system and the BIOS supports only a maximum processor speed of 700 MHz, the BIOS will detect a 700 MHz processor. This will limit the system's performance to 700 MHz.

Summary Intel developed the Classic Pentium architecture over three generations, moving from a 273-pin pin grid array (PGA) package in the first generation to a 296-pin staggered pin grid array (SPGA) in the later two. Later, more advanced versions of the Classic Pentium include the Pentium Pro, Pentium II, Pentium III, and Pentium 4. Advanced Micro Devices (AMD) manufactures several Pentium clone microprocessors. The two principal clones are the Athlon – a Pentium III clone, and the Duron – a Celeron clone that uses the AMD Socket-A specifications. Cyrix also produces Pentium clones, such as the Socket 370 compatible Celeron clone called the Cyrix III. A slot or socket is the physical connection between the motherboard and the CPU, and there are different designs to accommodate the needs of different processors. Early socket specifications include Sockets 1 through 7, Super Socket 7 and Socket 8. Proprietary slot designs, such as Intel's Slot 1 and Slot 2, and AMD's Slot A were adopted for a time, but recent processors use a socket design – the Pentium 4 for example uses Socket 423 and Socket 478. specifications. Some important CPU settings that may have to be configured are the bus frequency, the core voltage, the core-to-bus speed ratio, and the CPU type. If you use automatic CPU configuration, it's important that the BIOS version supports the parameters of the microprocessor, as a mismatch can reduce processor performance.

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Chipsets and bus architectures 1. Chipsets and bus speeds A chipset is the name given to a group of chips on the motherboard that control how data and instructions flow to and from the CPU. So the chipset handles all of the core functions of the motherboard, and its components include the memory controller, the external bus controllers, and the I/O controllers. When Intel released the Classic Pentium, it also introduced a powerful new chipset and the Peripheral Component Interconnect (PCI) bus architecture, designed to replace the older Industry Standard Architecture (ISA) specification. This new chipset design – based on a three-tier architecture – was very successful, and dominated the market. Later, Intel introduced a new chipset design (for the 800 series), called the Accelerated Hub Architecture, which as the name suggests, uses a hub interface architecture.

Note The major components of the three-tier chipset are a Memory Controller, a PCI-to-ISA Host Bridge, and an Enhanced I/O Controller. With the Accelerated Hub Architecture, there are two major components in the hub, which connects to the system bus. These are the  

Memory Controller Hub (MCH) I/O Controller Hub (ICH)

Memory Controller Hub (MCH) The Memory Controller Hub (MCH), is the faster end of the hub, and is often referred to as the North Bridge, a reference to the older, three-tier chipset design. It connects directly to the system bus. I/O Controller Hub (ICH) The I/O Controller Hub (ICH), or the Enhanced I/O Controller, is often referred to as the South Bridge, a reference to the older, three-tier chipset design. It is the slower end of the hub, and most I/O devices are connected to the hub though it.

The different buses in the Accelerated Hub Architecture run at different speeds. One factor affecting the speed of operation of a system is the rate of data transfer across the buses. For example, the CPU may operate at 1.1 GHz internally, whereas the system bus, or front-side bus, runs at 133 MHz. The PCI bus might run at 66 MHz, and the IDE bus could run at 100 MHz. The first system buses operated at 66 MHz, and were followed by system buses that ran at 100 MHz. Currently, most system buses operate at 133 MHz.

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Historically, the PCI bus has had standard operating speeds of 33 MHz and then 44 MHz. It now has a standard speed of 66 MHz. On some boards, there may also be an ISA bus, operating at a speed of only 8.33 MHz.

2. Expansion slots Expansion slots are the slots found on the motherboard into which expansion cards can be inserted. These slots connect to expansion buses – those buses on the board that run at a different speed to the system clock. Expansion slots use one of the following formats:   

8-bit 16-bit 32-bit

8-bit The PC bus slot is the best-known example of an 8-bit expansion slot. This was the standard for the original PC and PC-XT. The standard describes an 8-bit, bidirectional data bus, and 20 address lines for I/O. It provides six interrupts, control signals for I/O read/write operations, clock and timing signals, and three DMA control lines. The bus also includes memory-refresh timing signals, an I/O channel check line, and power and ground lines for plug-in adapters. 16-bit When Intel released the 286 processor, IBM created a new 16-bit expansion bus. This bus was originally called the AT bus, but, due to its widespread acceptance, is now known as the Industry Standard Architecture (ISA) bus. The 16-bit ISA slot ( the expansion slot for this bus ( is the most common expansion slot, and is even found on motherboards with 32-bit and 64-bit expansion slots. The ISA slot consists of two parts ( the 62-pin I/O connector used for older 8-bit expansion card buses and a 36-pin auxiliary connector. The ISA bus has more interrupts and DMA control lines than the PC bus, so the ISA bus can support more peripheral devices. However, for compatibility, the transfer speed of the ISA bus is the same as that of the PC bus – ISA bus designs run at 8 MHz or 8.33 MHz. 32-bit In the same way as the 286 processor led to the development of the ISA bus, newer 32-bit processors, such as the 80386DX and the 80486DX led to the development of 32-bit bus standards, each with their corresponding expansion slots. Early buses of this type included the Micro Channel Architecture (MCA) bus and the Extended Industry Standard Architecture (EISA) bus – an extension of the ISA bus. However, the MCA and EISA, as well as VL buses have now been replaced by the PCI bus, and several PCI slots are found on most motherboards today.

3. Local bus architectures

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The term local I/O bus, or local bus, describes high-speed buses that run in synchronization with the system clock, and so with the CPU. These buses are faster than expansion buses such as the ISA bus, but usually slower than the system bus. Types of local buses include   

the VESA bus the AGP bus the PCI bus

the VESA bus The Video Electronics Standards Association (VESA) bus, also known as the VL bus, was developed by the Video Electronics Standards Association in order to handle the increasing need for fast video data transfer associated with GUI based operating systems such as Windows 95. Devices attached to the VESA bus could interface directly with the system bus or front-side bus (this was called the local bus), so the devices could operate at the same speed as the system bus. For practical purposes though, the VESA bus had a maximum clock speed of 33 MHz. Today, the VESA bus is no longer manufactured and has been replaced by the PCI bus. the AGP bus The Accelerated Graphics Port (AGP) bus is a 32-bit bus designed specifically for the transfer of video graphics data. The AGP itself is similar to a PCI slot, but only one AGP will be found on the motherboard. Recent versions of the AGP bus are faster than any other bus on the motherboard, apart from the system bus. the PCI bus The Peripheral Component Interconnect (PCI) bus is a low-cost, high-performance bus with the Plug and Play (PnP) capability to configure installed cards automatically. It can also expand to accommodate new microprocessors and peripheral devices. The PCI peripheral device has 256 bytes of onboard memory, which holds information about the device type. The peripheral device acts as a controller for a mass storage device, network interface, display, or other hardware. The PCI bus has replaced the ISA bus as the most common form of bus.

A typical PCI slot is a white, 124-pin connector, which uses multiplexed address and data lines. It includes signals for interrupt, control, error reporting, arbitration, and cache support. The slot itself is a bit shorter than an ISA slot. PCI buses are available as  

32-bit 64-bit

32-bit The 32-bit PCI bus is the most common type, and has a maximum data transfer rate of 132 Mbps at a clock frequency of 33 MHz ( the same as that used in the VESA bus. However, this bus could be used with a processor running at a higher frequency. It could also handle 64-bit addressing using two 32-bit PCI cycles –referred to as Dual Address Cycles (DAC). So the 32-bit bus could be used with 64-bit processors. The 32-bit PCI bus uses a supply voltage of 5 V or 3.3 V of DC.

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64-bit PCI version 2.2 defined a 64-bit extension to the 32-bit bus, which required a new slot design. The 64-bit bus can run at 66 MHz, which allows a maximum theoretical throughput of 266 Mbps. The 64-bit bus uses a supply voltage of 3.3 V of DC. The back part of the new slot is compatible with the 32-bit design, and adapters placed in this part of the new slot can operate at either the 5 V or 3.3 V DC power levels.

The PCI bus supports Plug and Play (PnP), and to enable PnP, the bus must work in tandem with the BIOS, the peripheral devices, and the operating system. Information on the system resources used is stored in a special area of the CMOS or flash ROM known as the Extended System Configuration Data (ESCD) area. During the bootup detection phase, the BIOS compares the current system configuration with that stored in the ESCD area. If they are the same, the boot process continues as normal. However, if the configuration is different, maybe as a result of inserting a new PnP device, then the BIOS will reconfigure the system resources. Each PnP device is polled, to check which resources it requires (system resources cannot be randomly allocated to PnP devices), and the appropriate resources are assigned. The BIOS then updates the ESCD area, and the boot process continues.

4. AGP slots Newer Pentium processors – from the Pentium II on – and the associated chipsets, support AGP technology. This was developed in response to a need for greater video bandwidth than the PCI bus could be expected to offer. Intel introduced the AGP standard as a 32-bit video channel that runs at 66 MHz in 1x video mode. Its high-speed modes include AGP 2x (with a bandwidth of 533 Mbps) and AGP 4x (1.07 Gbps bandwidth). The most recent AGP specification defines another mode, AGP 8x, with a bandwidth of 2.1 Gbps. Although the original AGP specification was based on PCI, AGP is more advanced than PCI, and offers other features. One major difference is that a direct channel connects the AGP graphic controller to the MCH – or the North Bridge. This removes video traffic from the PCI bus and the increased speed resulting from this link allows video data to be stored in RAM instead of in video memory. A motherboard contains one AGP slot supported by a Pentium/AGP-compliant chipset. The AGP slot is similar in appearance to the PCI slot, but is colored brown and offset slightly from the PCI slots to avoid confusion. There are several subtle differences between AGP slots, depending on the voltages they provide. The 1.5 and 3.3 V slots have a notch or key at opposite ends of the slot, whereas the AGP universal slot, which has no notch, can accommodate both 1.5 and 3.3 V AGP cards.

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All these slots have a 132-pin connector, but another standard, AGP Pro, specifies a longer, 180-pin slot. Some portable and single-board systems even include the AGP function directly on the board, rather than using a slot connector.

Table of expansion bus specifications Expansion bus specifications Bus type

Data bits

Address bits

Interrupt channels

DMA channels

Transfer rate

PC

8

20

6

4

1 Mbps

ISA

16

24

11

8

16 Mbps

VESA

32/64

32

1

None

150/275 Mbps

PCI 2

32/64

32

3

None

132/264 Mbps

PCI 2.1

32/64

32

3

None

264/528 Mbps

PCI 2.2

64

32

3

None

264 Mbps

AGP

32

32

3

None

266/533/1070 Mbps

When you replace a motherboard, you need to ensure that it has the right expansion slots to support the types of adapter cards that your system requires. There is some upward compatibility between PC-bus, ISA, EISA, and VESA cards. However, most PC-bus cards can't be installed in ISA, EISA, VESA slots. Most ISA cards fit into EISA and VESA slots, but the reverse is not true – EISA and VESA cards don't fit into ISA slots. MCA and PCI slots are not compatible with other bus types. Sometimes boards have a communication and networking riser (CNR) to fit a small network card, soundcard, or modem. Alternatively, they may have an audio modem riser (AMR) to fit a small modem or sound card. This is an inexpensive alternative because most of the logic is in the motherboard chipset. You can add a card at low cost, without a PCI or ISA slot.

Summary The chipset is a group of chips on the motherboard that control how data and instructions flow to and from the CPU, handling all of the motherboard's core functions. Intel have defined the Accelerated Hub Architecture chipset design where the hub is made up of two different components – the Memory Controller

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Hub (MCH) and the I/O Controller Hub (ICH) – which are connected to various buses on the motherboard. A motherboard can have 8-bit, 16-bit, and 32-bit expansion slots, corresponding to different types of bus. The 8-bit bus, or PC bus, is a bidirectional data bus with 20 address lines for I/O. The ISA bus is a 16-bit bus, and its expansion slot – consists of a 62-pin I/O and a 36-pin auxiliary connection. PCI is a 32-bit bus standard and is the most commonly used bus today. The Video Electronics Standards Association (VESA) local bus, the Micro Component Architecture (MCA), and the Extended Industry Standard Architecture (EISA) bus are examples of buses that are no longer used. A local bus is a high-speed bus that runs in synchronization with the system clock, and hence the CPU. These buses are faster than expansion buses but usually slower than the system bus. Examples of local buses include VESA, Peripheral Component Interconnect (PCI) and AGP (Accelerated Graphics Port). The PCI bus is a high-performance bus with Plug and Play (PnP) capabilities that can accommodate new microprocessors and peripheral devices. A typical PCI slot uses a white 124-pin connector and the bus itself is available as a 32-bit or a 64-bit bus. The AGP bus was developed to support greater video bandwidth than the PCI bus could offer. Although the original AGP specification was based on PCI, AGP is more advanced than PCI, a major difference being that a direct channel connects the AGP graphic controller to the MCH (or the North Bridge). Only one AGP is found on the motherboard.

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BASIC NETWORKING Types of network ports 1. Standard I/O ports I/O ports link computers to peripheral devices or to other computers. The standard I/O ports for connecting computers to peripheral devices include the   

RS-232C serial port female 25-pin D-shell (DB-25F) parallel port game port

The DB-25F port on the computer's back panel is the IBM equivalent of the 25pin Centronics port, which is the standard port for printers and other parallel devices. The DB-25F port usually connects to the Centronics parallel port on a printer via cable. The Registered Jack (RJ-45) Ethernet or British Naval Connector (BNC) coaxial ports are the standard ports for connecting networked computers. The RJ-45 jack is an 8-pin connector resembling a telephone socket. The BNC resembles a TV aerial jack. Both these connectors are located on a network interface card (NIC). Earlier computers used the Advanced Technology (AT) system to arrange ports and devices. Devices in this system connect to the ports through the expansion slots on the computer's back panel. The number and order of slots on the back of the PC varies from system to system, but AT systems usually have eight slots. A typical AT system has a combination of standard and non-standard ports – for example a video port, a small computer system interface (SCSI) port, an internal modem port, and a NIC. The video port and game port are both 15-pin male ports, but the video port has three rows of pins and the game port has two rows. This prevents you from connecting the monitor to the joystick port, or vice versa. In AT systems, standard I/O ports connect directly to the motherboard via ribbon cables. Disk drives also use ribbon cables. In an example, a ribbon cable connects the mouse port to the first Component Object Model port (COM1) on the motherboard. Another cable connects the parallel printer port to the first Local Printer Terminal 1 (LPT1) port on the motherboard.

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On the back panel, COM1 has a DB-9M serial jack and COM2 has a DB-25M jack. The parallel port also has a 25-pin connector, but COM2 is male whereas the parallel port is female. This prevents you from connecting parallel devices – like printers, webcams, or zip drives – to the serial port. In AT computers, most non-standard I/O ports are mounted on adapter cards inserted into expansion slots on the motherboard. By contrast, the keyboard usually plugs into a 5-pin Deutsche Industrie Norm (DIN) socket mounted directly on the motherboard.

Note DIN is the German national industry standard for computer components. The Advanced Technology Extended (ATX) system has replaced the AT model in later computers. In ATX computers, most ports are built onto the motherboard. Devices connect directly to the system without using adapter cards or ribbon cables, like the keyboard in AT systems. This is known as a vertical stack form factor (VSFF). However, ATX systems still allow you to install adapter cards for additional devices. A typical ATX system includes the following ports:     

PS/2 connectors Universal serial bus (USB) port Printer port COM1 and COM2 ports Game and audio ports

PS/2 connectors In ATX systems, the mouse no longer uses the COM1 serial port. Instead, it plugs into a 6-pin mini-DIN socket known as a PS/2 port. The PS/2 standard has replaced the larger DIN socket as the default port for input devices like keyboards and mouse devices. Because the mouse and keyboard use the same type of port, you should be careful when connecting these devices to a system. The mouse port is always located above the keyboard port. Universal serial bus (USB) port A standard ATX system has two USB ports. A USB port is an external data bus that supports many peripheral devices, including printers, flash sticks, and scanners. Printer port Like AT systems, ATX computers include a DB-25F parallel printer port. However, this port is mounted directly on the motherboard, so there is no ribbon cable that can malfunction. COM1 and COM2 ports In ATX systems, both COM ports use DB-9M connectors instead of the 9-pin and 25-pin configuration of older systems. This makes it easier to distinguish the serial ports from the parallel printer port. Because ATX systems include a dedicated PS/2 mouse port, the COM ports are seldom used to connect mouse devices.

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Game and audio ports Although they no longer share an adapter card, the game and audio ports are still grouped on the back panels of ATX systems. As in AT systems, the game port uses a DB-15F connector. And the speaker, line-in, and microphone (MIC) ports still use Radio Corporation of America (RCA) audio jacks.

It's important to distinguish between the AT and ATX systems, particularly when buying computer components. For example, when purchasing a mouse, you need to know if the computer has a PS/2 port or only a serial (COM1) port.

Typical AT and ATX I/O ports Typical I/O ports in AT and ATX systems Port name

AT connector

ATX connector

COM1

DB-9M

DB-9M

COM2

DB-25M

DB-9M

Game

DB-15F (2 row)

DB-15F (2 row)

Keyboard

5-pin DIN

PS/2 6-pin mini-DIN

LAN

BNC/RJ-45

BNC/RJ-45

LPT

DB-25F

DB-25F

Modem

RJ-11

RJ-11

Mouse

none

PS/2 6-pin mini-DIN

SCSI

Centronics 50-pin

Centronics 50-pin

Sound

RCA mini-jacks

RCA mini-jacks

VGA

DB-15F (3 row)

DB-15F (3 row)

Most of the port connectors are the same in both systems. The only exceptions are the COM2, keyboard, and mouse ports.

2. Serial ports During serial communication, devices transmit single bits of data at a time. External serial transmission is used mainly when devices are far apart. For example, if a printer is more than 3 meters away from the computer it connects to, you could plug it into the computer's COM2 port using a serial cable. There are two serial transmission modes that depend on how each device times data transfers – synchronous transmission and asynchronous transmission. Synchronous transmission uses a clock signal that is separate from the data signal. This is generally achieved by using a separate wire. Communication therefore happens during the pulse or tick of the timing signal. You use this method to transfer large amounts of data quickly.

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Data transfer within a computer – for example between disk drives and the motherboard – is usually synchronous, because this allows for a constant transfer rate. Asynchronous transmission doesn't use a constant clock signal. Instead, special signaling bits are added to the beginning and the end of the data. The beginning bit is known as the start bit. The next number of bits (generally 8) are known as the data bits. Finally, there are 1 or more stop bits to indicate that the data has finished. Most external devices that use the standard serial ports, COM1 and COM2, transfer data asynchronously. Both sending and receiving devices must agree on the number of data bits and stop bits whether parity checking is used or not. If both sending and receiving devices aren't configured, the same data communication can't occur. The computer synchronizes its internal clock with the serial ports using a universal asynchronous receiver-transmitter (UART) adapter. The UART determines the computer's maximum baud rate.

Note Bauds are the electrical state changes on a data communications line that transmit information. The baud rate indicates the number of signals transmitted every second. This is also expressed as bits per second (bps). The following versions of UART are currently in use:  

8250 UART advanced UART

8250 UART Older 8250 UARTs transfer data in bits of 5–8 characters at a programmable rate of 50–9600 baud. An 8250 UART times the transfer of data with a programmable interrupt system that informs the CPU clock when data is being sent to or from a port. advanced UART Advanced models, like the 16550 UART, use built-in buffers instead of an interrupt system, with a maximum data transmission rate of 115 Kbps. Like the older model, 16550 UART adapters also diagnose communication problems, like false start bits, and handle line breaks and bit types.

Serial cables use DB-25F connectors. Although the RS-232C standard has 25 pins, each application assigns only nine of the pins a function. This usually includes a number of control lines. The other pins are reserved as backup lines. The RS-232C standard sets the acceptable voltage level for the pin signals. The signals that communicate with components on the digital logic level, like gates and buses, have a maximum transfer rate of 200 Kbps. An RS-232 cable can be up to 15 meters, and an RS-232C cable can be up to 30.5 meters in length. There are two basic pin configurations for serial cables: 

9-pin to 25-pin

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

25-pin to 25-pin

9-pin to 25-pin In a 9-pin to 25-pin configuration, wires connect the pins on the DB-9F cable connector to any nine pins on the computer port. For example, you can configure pin 7 on the modem port and pin 4 on the computer to send requests, pins 8 and 5 to send clear requests, and pins 9 and 22 to be the ring indicators. 25-pin to 25-pin In the basic 25-pin to 25-pin configuration, nine pins on the computer port connect to nine pins on the cable port. For example, you can configure pin 2 to transmit data, pin 3 to receive data, pin 7 to be the ground signal, pin 8 to detect a carrier, and pin 20 to indicate when the data terminal is ready. In this configuration scheme, you can assign a function to any of the pins on each port.

You can wire both 9-pin to 25-pin and 25-pin to 25-pin configuration schemes in two ways. In a one-to-one or straight-through wiring scheme, the pins on each port connect to the corresponding pin on the other port. In a crossover wiring scheme, the ports assign the same functions to different pins. You can connect the ports of two serial devices that are near each other without a modem using a crossover or null modem cable. A null modem connection allows bidirectional communication using a crossover wiring scheme. The ports on either end of the cable connect the Data Terminal Ready and the Data Set Ready pins, the Request to Send and the Clear to Send pins, and the Transmit Data and Receive Data pins. DOS assigns the serial ports COM names. Most computers have two COM ports, but advanced systems support a maximum of four COM ports. If DOS detects additional COM ports during startup, it will call these COM3 and COM4. During startup, each COM port is assigned an interrupt request line (IRQ) channel and a hex address. For example, most systems assign COM1 3F8h and IRQ Channel 4, COM2 2F8h and IRQ3, COM3 3E8h and IRQ4, and COM4 2E8 and IRQ3.

Note A hexadecimal address is a numbering system using 16 digits, including the numbers 0–9 and the letters A–F. Hexadecimal notation is often used to display memory addresses.

3. Parallel ports The ports found on parallel devices – like printers – usually adhere to the Centronics standard.

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This port arrangement lets devices transfer eight bits simultaneously by providing eight data lines to send or receive data, and another ten to transfer control signals – also called handshaking signals – to and from the computer. Some transfer control signals can inform the computer in the event of errors – for example, if the printer is busy or out of paper – and others can allow the computer to select an input device or initialize a printer. Most parallel cables have a Centronics connector on the printer's side and a Dshell connector on the computer's end. Originally, both connectors had 36 pins. However, the newer Standard Parallel Port (SPP) interface requires a 25-pin male connector on the computer's end of the cable. Like SPP ports, the enhanced parallel port (EPP) and extended capabilities port (ECP) standards allow bidirectional communication between devices. However, EPP and ECP offer much faster transfer speeds than the Centronics interface. This allows computers to support devices that require very fast data transfer speeds. Parallel cables are shielded to minimize electromagnetic field interference (EFI) from radio waves generated by the computer or the I/O device. Because the copper used in parallel cables is prone to EFI, the recommended length of a standard parallel printer cable is 3 meters. Like serial ports, each printer port is assigned a logical device name, an IRQ number, and a hex address during startup. Some computers have two parallel ports. DOS usually assigns LPT1 address 378h and IRQ7, and LPT2 address 278h and IRQ5.

Note You can change the port address or the IRQ settings by changing the jumpers on the port. You can also change the IRQ settings in the complementary metal oxide semiconductor (CMOS) setup.

4. USB, FireWire, and infrared ports A wide variety of serial devices can connect to a computer via universal serial bus (USB) ports. A single USB port can support up to 127 devices at a time, because it allows devices to form a daisy-chain network. This means that certain devices can act as connection hubs for other devices to link to, instead of connecting to the computer itself. An important feature of USB is that it allows hot swapping or hot plugging. This means that you can add or remove internal or external devices to the computer while it is plugged in. USB devices are also Plug-and-Play (PnP) compatible, so a system detects and configures them automatically. A USB cable has four wires, including 90-ohm twisted-pair wires used to send differential (D+ and D-) signals. This minimizes interference and data loss.

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The host system supplies power to the root hub. In turn, each USB device gets power from the root hub or from another USB device acting as a hub via a +5 volt DC Vbus power cable. Slower devices use USB Version 1, which allows data transfer at 1.5–12 Mbps, whereas Version 2 allows a maximum data transfer rate of 480 Mbps. However, the number of devices and their distance from a system influence the speed of a USB connection. For example, the maximum cable length for a fullspeed USB device is five meters, whereas slow-speed devices have a cable length of 3 meters. USB ports use the following kinds of plugs:  

Series A Series B

Series A Devices with permanent USB cables attached – for example keyboards and mouse devices – use series A plugs. Series B Devices with removable USB cables, like scanners and printers, have Series B plugs.

Devices that require faster data transfer rates than USB, like webcams and web phones, can use FireWire connectors. Like USB, FireWire allows hot swapping, PnP, and daisy-chaining. Although each FireWire connector can support a maximum of 63 devices, a FireWire network can include 1023 buses. A FireWire port usually has a 6-pin connector and a 4-pin to 6-pin converter, and the cable itself consists of two twisted-pair wires. Windows 9x, Windows NT, and Windows 2000, and Windows Server 2003 all support FireWire. The Home AV Interoperability (HAVi) standard also allows networks without a host computer to support PnP FireWire devices. The P1394b standard supports data transmission speeds of up to 3.2 Gbps. It also supports transport media – such as glass, plastic optical fiber, and Category 5 copper cable – that extend the maximum cable length to 100 meters The Infrared Data Association (IrDA) provides a wireless peripheral connection standard based on infrared light technology. An IrDA-compliant port standard provides wireless communication using infrared with devices such as personal digital assistants (PDAs), notebook computers, and printers. Additionally, infrared light technology enables transfers between computer communications devices such as modems and local area network (LAN) cards.

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The four main IrDA protocols are    

Fast IrDA protocol (IrDA-FIR) Infrared Image Transfer Protocol (IrTran-P) Infrared printing protocol (IrLPT) Serial IrDA protocol (IrDA-SIR)

Fast IrDA protocol (IrDA-FIR) IrDA-FIR is a fast infrared protocol that provides a high-speed serial port interface with transmission speeds up to 4 Mbps. Infrared Image Transfer Protocol (IrTran-P) IrTran-P provides a digital image transmission standard for communications with digital image capture devices. Infrared printing protocol (IrLPT) IrLPT provides a wireless interface between a computer and a character printer. Serial IrDA protocol (IrDA-SIR) IrDA-SIR is the standard infrared protocol. It provides a standard serial port interface with transmission speeds up to 115 Kbps.

Although the IrDA protocols specify communication ranges up to 2 meters, most IrDA device specifications state 1 meter as the maximum range. IrDA transmissions require half-duplex mode, as well as a clear line of sight between the transmitter and receiver.

Summary I/O ports connect computers to peripheral devices or to other computers. The Advanced Technology Extended (ATX) system has replaced the earlier Advanced Technology (AT) system. A typical ATX system includes the following ports – Personal System/2 (PS/2) connectors, universal serial bus (USB), printer, COM1 and COM2, game, and audio ports. Serial transmission can occur in synchronous or asynchronous mode. Serial ports have COM names, and most computers have two COM ports. During startup, each COM port receives an interrupt request line (IRQ) channel and a hex address. Parallel ports enable devices to transfer eight bits simultaneously. The extended parallel port (EPP) and extended capabilities port (ECP) standards allow fast, bidirectional communication between devices. Computers typically have two parallel ports – LPT1 and LPT2. Each receives an IRQ number and a hex address during startup. Universal serial bus (USB) ports enable you to connect a wide variety of serial devices to a computer. Devices that require faster data transfer rates can use FireWire connectors. Infrared ports enable wireless communication between devices such as modems and local area network (LAN) cards

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Network cables 1. Coaxial and UTP cabling Network cabling transmits data between computers. Types of media that can transmit network data include    

copper cabling fiber-optic cabling infrared light wireless radio frequency (RF) signals

copper cabling Copper cabling includes twisted-pair and coaxial cabling. In twisted-pair cabling, two or more wires are twisted together to reduce the susceptibility of signals to noise interference. The reduction in noise level depends on the number of twists in each foot of wire. A coaxial cable has a single or multistrand copper conductor in its center and a protective braided copper shield around it. fiber-optic cabling Fiber-optic cabling consists of plastic or glass and carries voice or digital data in the form of light pulses. infrared light In infrared LANs, an Infrared Data Association (IrDA) link provides the high-speed transmission media between Ethernet devices. wireless radio frequency (RF) signals Usually, a wireless LAN consists of a wireless LAN adapter card and a radio frequency (RF) antenna. Wireless LANs connect computer nodes using high-frequency radio waves.

Important coaxial cables include    

RG58 used by ThinNet Ethernet RG59 used for cable TV and VCR transmission RG6 – with a greater shielding than RG59 – used for satellite dish signals and video RG8 used by ThickNet Ethernet

A coaxial cable is usually covered with extruded PVC (polyvinyl chloride), which isn't safe to use in the areas between the floors of buildings. In these cases, you use a more expensive plenum cable covered with Teflon. Twisted-pair cabling can be  

Unshielded Shielded

Unshielded

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Unshielded twisted-pair (UTP) cable contains four pairs of individually insulated wires. Shielded Like unshielded twisted-pair (UTP) cable, shielded twisted-pair (STP) cable contains four pairs of wires. However, an additional foil shield surrounds the four-pair wire bundle. The shield provides a grounded path to carry induced electrical noise and crosstalk away from the conductors in the cable.

The Electronic Industry Association (EIA) and the Telecommunications Industry Association (TIA) have established UTP cable specifications. The UTP wiring categories (CATs) depend on grades of cable, along with connector, distance, and installation specifications. Cat 5 and Cat 5e are the most widely used specifications. The connector and color-coded connection scheme specified for four-pair, Cat 5 UTP network cabling is shown. The figure also provides the color code for attaching the connector to the cable. Standard 586-B connections are more common than 586-A connections.

UTP cable categories Table1: UTP cable category ratings Category Maximum bandwidth

Wiring types

Applications

Cat 3

16 MHz

100 ohm UTP Rated 10 Mbps Ethernet 4 Mbps Token Ring Category 3

Cat 4

20 MHz

100 ohm UTP Rated 10 Mbps Ethernet 16 Mbps Token Category 4 Ring

Cat 5

100 MHz

100 ohm UTP Rated 100 Mbps TPDDI 155 Mbps Category 5 Asynchronous Transfer Mode (ATM)

Cat 5e

350 MHz

100 ohm UTP Rated 1.2 Gbps 1000Base-T high-speed Category 5E ATM

Cat 6

Above 350 MHz

100 ohm UTP Rated More than 1.2 Gbps 1000Base-T Category 6 high-speed ATM

2. Fiber-optic cabling By carrying voice or digital data in the form of light pulses, fiber-optic cabling provides potential signaling rates in excess of 200,000 Mbps. However, current access protocols limit signaling rates to 1 Gbps. There are two modes of fiber-optic cable. Single-mode cable uses injection laser diodes (ILDs) to send data. It is a highbandwidth, expensive cable. Multimode cable uses light-emitting diodes (LEDs).

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After digital or voice data is converted into light signals, a laser diode introduces the light signals into the cable. At the end of the cable, a light-detecting circuit transforms the signals into usable information. Light traveling through a fiber-optic cable doesn't attenuate – lose energy – as fast as electrical signals traveling along a copper conductor. So in fiber-optic cabling, the segment lengths between transmitters and receivers can be much longer – sometimes up to many kilometers. To minimize attenuation, the end of the cable must be exactly aligned with the receiver and it must be free from scratches, film, or dust. Fiber-optic cables are more secure than copper cables. Light introduced into the cable at one end can leave the cable through the other end only. And usually no signal level matching is necessary between the transmitter and receiver. Fiber-optic cable uses a number of connectors to align the end of the cable with the receiver. The most commonly used are subscriber connectors (SC) and straight tip (ST) connectors. The SC connector is the main connector for fiber-optic Ethernet networks, although ST connectors are also sometimes used.

Summary Media used for data transmission include copper and fiber-optic cabling, infrared light, and radio frequency (RF) signals. Copper cabling includes coaxial cabling, as well as shielded twisted-pair (STP) and unshielded twisted-pair (UTP) cabling. Various UTP wiring categories (CAT) exist. Fiber-optic cabling carries voice or digital data in the form of light pulses. Because light signals don't attenuate as fast as electrical signals, fiber-optic cables can be very long. They're also more secure than copper cables. Fiberoptic cabling generally uses straight tip (ST) connectors and subscriber connectors (SC) to align the end of the cable with the receiver.

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Network types, topologies, and architecture 1. Peer-to-peer and client/server networks A network can be defined as a group of devices, which are connected together in some way so that data and resources can be shared between the devices. As they are shared, the issue of how control over the data and resources are managed is a crucial one for any network. Two kinds of networks in which control is managed in two very different ways are  

client/server peer-to-peer

client/server A client/server network includes one or more main computers, called servers, which provide centralized control. All the other computers in the network connect to the servers, and these are called clients. The clients use the resources provided by the server, which can manage and control access to other devices, such as disk drives and printers. Advantages of the client/server network are that it allows centralized administration and makes it easier to control data and resource security. peer-to-peer A peer-to-peer network is a network in which all computers have equal capabilities and responsibilities. All the nodes in the network share data and resources, and control over this is managed at each local node. The nodes in a peer-to-peer network can serve as both clients and servers to perform different functions, depending on circumstances. This arrangement is effective for small networks – those with a small number of nodes – but it is not commonly found in larger networks, due to security and reliability concerns.

2. The characteristics of LAN topologies Each network has a specific topology – or layout – determined by the way in which the nodes in the network are connected to each other. A topology is either physical or logical. The logical topology describes the way in which data flows in the network. The physical topology describes the physical layout of the network – in other words, how the network actually looks. The logical topology may be different from the physical topology of the same network. One of the key factors affecting topology is the geographical layout of a network. In this regard, networks can be divided into two broad categories – local area networks (LANs) and wide area networks (WANs). As the term implies, a LAN is a network that is confined to a limited area, an office block for example. In contrast, a WAN can extend over much greater distances – between different cities, countries, or continents. The most common LAN network topologies are shown.

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   

Bus Mesh Ring Star

Bus In a bus topology, all the computers in the network connect to a central cable – the bus or backbone. Each computer has a unique address to differentiate it from other computers. Any computer on the network can send data to other computers, via the backbone, using the network address. Only one computer may send data at any one time, and other computers along the bus for which the information is not intended will ignore the information. A drawback of the bus topology is that if a break occurs at any point in the backbone, the entire network is disabled. Mesh A mesh topology is in a sense the most complete network type, in which each computer has a point-to-point connection to every other computer in the network. The main advantage of this topology is the high degree of redundancy built into the network – if a path between two computers in the network fails, they can still exchange data using other paths in the network. However, this degree of redundancy is expensive to set up and can be difficult to maintain. For these reasons, a partial mesh topology, in which every node is not connected to every other node so there are fewer redundant data paths to configure and monitor, is often preferred. Ring In a ring topology, all computers connect to adjacent computers in the shape of a closed loop. Data travels in one direction around the loop.

Token Ring networks use this kind of topology. In such a network, special data packets are circulated around the network, in one direction. These special data packets can be used by individual nodes in the network to exchange data. There is a repeater built into every computer in a ring topology that regenerates, or boosts, every signal that the computer receives. Ring topologies offer very high data transfer rates, but can be difficult to manage and reconfigure because if the ring is broken, or if any node in the ring fails, the entire network is brought down. Some network technologies, such as Fiber Distributed Data Interface (FDDI), have a secondary ring built in, in case of failure of the primary ring. Star In a star topology, all computers connect to a central computer – or hub – via which they communicate. The central hub polls each computer in the network to see if it has any information that needs to be sent to another computer. If a computer needs to transfer information, the hub gives it a specific time period to transmit the information. The computer then sends the information to the central hub, which transmits it to the destination computer. A star topology is easy to install, reliable, and easy to manage – it's all done from the central hub. If one computer in the network fails, it doesn't affect other computers in the network.

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However, if the central hub fails, it affects all the computers in the network

3. Characteristics of the Ethernet protocol The most widely used LAN architecture today is Ethernet, which is actually a set of standards, created and maintained by the International Electrical and Electronic Association (IEEE).   

How Ethernet works Ethernet connections Ethernet specifications

How Ethernet works An Ethernet uses a bus or star-bus topology, the difference is defined in terms of the physical topology, but the basic operation of the network is the same with both topologies.

The signals on an Ethernet LAN are managed by a protocol called Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Every node in a network using CSMA/CD can transmit on the network. Before a node transmits, however, it listens to the network to check if another node is transmitting. If another node is transmitting, the node wanting to transmit waits for a randomly selected period of time before attempting transmission again. If the node detects that the network is not in use, it transmits a signal, and listens for a collision. A collision occurs when two or more nodes try to transmit packets at the same time – in other words, when the nodes try to transmit simultaneously. When a collision occurs, the signals sent by the nodes are damaged, and must be retransmitted. So the nodes are alerted of the collision and execute a backoff algorithm that randomly schedules retransmission of the signals. Because this is a random process, it is highly unlikely that the nodes will try to retransmit the signals at the same time. Most collisions are resolved in microseconds. If there is no collision, the node broadcasts a signal onto the network. All of the nodes check the signal. The node or group of nodes for which the signal is intended process the signal, whereas the other nodes, for which the signal is not intended, ignore it. Ethernet connections Different Ethernet standards use different types of connectors and cables. The most common types of cable are coaxial cable and unshielded twisted pair (UTP) cable, although some standards may use fiber-optic and shielded twisted pair (STP) cable. Two types of coaxial cable are used in Ethernet networks. The original Ethernet specification called for a thick coaxial cable with a 3/8 inch diameter, so the specification is known as Thick Ethernet, or Thicknet. A later specification uses smaller, more flexible cable with a 3/16 inch diameter, and is known as Thin Ethernet, or Thinnet. A Thicknet uses a 15-pin D-type connector on the PC. This connector is known as an Access Unit Interface (AUI) or Digital, Intel, Xerox (DIX) connector. A British Naval Connector (BNC) is used in a Thinnet. Each network card is connected to the backbone using a T connector, which must be used. Special terminators are inserted into one end of the connector at the end of the chain.

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Other Ethernet specifications use UTP cabling, with the standard RJ-45 connector, which is similar in appearance but larger than the RJ-11 connector. RJ-11 connectors are used with modems and telephones. The pins on the RJ-45 connector are numbered, and the color of the wire in the cable is used to identify which wire belongs to which pin. The connector itself is placed into the corresponding port on the network card. Ethernet specifications In 1980, the IEEE responded to the need for LAN standard by initiating project 802, named after the year and month (February) in which it began. These standards are divided into 16 different categories, and the Ethernet standard is 802.3. There are a number of different Ethernet standards. The original standard was simply known as 802.3, and defined a maximum data transfer rate of 10 Mbps. There are a number of different implementations of the original 802.3 standard, referred to using the IEEE XXBaseYY nomenclature, where XX is the maximum data transfer rate, and YY refers to the cabling used in the network or the maximum segment length. So for example, the original Ethernet specification is referred to as 10Base5 – Ethernet using Thick Coaxial Media (Thicknet), where the maximum segment length is 500 meters. The 10Base2 standard is the Thin Ethernet, or Thinnet – for which the maximum segment length of the thinner coaxial cable is almost 200 meters (185 meters exactly). Other 802.3 implementations include 10BaseF (Ethernet over fiber media) and 10BaseT (Ethernet over twisted pair media). In time, the IEEE developed an Ethernet standard which allowed data transfer rates of up to 100 Mbps, ten times faster than the original Ethernet. This standard is defined by the IEEE 802.3u specification and is known as Fast Ethernet. There are three common Fast Ethernet implementations – 100BaseTX (two pairs of wires in Category 5 UTP cable, which is the most popular implementation), 100BaseFX (fiber optic), and 100BaseT4 (four pairs of wires in Category 3 cable, or higher). The IEEE have developed a later Ethernet standard – IEEE 802.3z – which represents a ten fold increase in the data transfer rate over Fast Ethernet to 1000Mbps, or 1 Gigabit per second (Gbps). For this reason, the specification is known as the Gigabit Ethernet. One Gigabit Ethernet specification is 1000BaseT, which uses copper-based unshielded twisted pair (UTP) cable. Work is underway on another specification (IEEE 802.3ae) for the 10 Gigabit Ethernet, or 10GbE.

The different Ethernet specifications and implementations provide a choice of different data transfer rates and transmission media, and support networks of different physical size.

Selected Ethernet specifications Common Name/Implementation

Cable Type

Maximum Segment Length

Transfer Rate

Thin Ethernet or Thinnet/10Base-2

Coaxial (3/16 inch diameter, RG-58)

185 m

10 Mbps

Thick Ethernet or Thicknet/10Base-5

Coaxial (3/8 inch diameter, RG-8)

500 m

10 Mbps

Ethernet/10Base-T

Cat 3 UTP/STP

100 m

10 Mbps

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Selected Ethernet specifications Common Name/Implementation

Cable Type

Maximum Segment Length

Transfer Rate

Fast Ethernet/100Base-TX

Cat 5 UTP

100 m

100 Mbps

Fast/Ethernet/100Base-FX

Fiber Optic

412 m

100 Mbps

Fast Ethernet/100Base-T4

Cat 3 UTP and above 100 m

100 Mbps

Gigabit Ethernet/1000Base-T

Cat 5 UTP

1 GBps (1000 Mbps)

100 m

4. Token Ring and FDDI LANS Ethernet is very popular – currently, approximately 85 percent of the world's computers that connect to a LAN use it. There are other LAN technologies, however, including Token Ring and fiber distributed data interface (FDDI). Token Ring is a LAN technology developed by IBM and standardized by the IEEE using one of the 16 802 categories, 802.5 (Ethernet is 802.3). A Token Ring network uses a physical star topology, in which the network nodes are connected to a central device known as a Multistation Access Unit (MSAU, or MAU). However, the MAU is wired in such a way that the nodes behave as if they were connected in a logical ring. Such an arrangement is sometimes called a star ring topology. All the nodes in a Token Ring network circulate a token – a special kind of data packet, which travels in one direction from one node to the next. Each node in such a network effectively acts as a repeater, so that the token is regenerated by each node. Only one token may be on the network at any one time, so the kind of collisions you encounter in an Ethernet are impossible in a Token Ring network. When a node wishes to transmit, it waits for the token to reach it, and – if the token is free – marks it as busy, which means no other node in the network can claim it for a set period of time. If it has a free token and wishes to transmit, a node appends any data to the token, and sends it to the next node on the ring. The token circulates until it reaches the intended recipient, which saves the data, and places the token back onto the network. When the token reaches the sender, the receiving node checks that the data was sent correctly and releases the token so that another node on the network can use it. Many Token Ring networks use shielded twisted pair (STP) cable, with either an IBM data connector (IDC) or a universal data connector (UDC). However, some

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Token Ring networks use UTP or fiber-optic cable. Token Ring networks can support data transfer rates of 4 or 16 Mbps – a 100 Mbps version was in the process of being developed, but abandoned because of the emergence of the Gigabit Ethernet. For this and other reasons, Token Ring is considered a legacy technology. A fiber distributed data interface (FDDI) network is a network standard similar to the Token Ring protocol but designed for use with fiber-optic cabling. There is a version of FDDI though – Copper Distributed Data Interface (CDDI) – that runs over copper cabling. An FDDI network uses a ring topology with two counter-rotating rings instead of one, and provides a data transfer rate of 100 Mbps. One of the rings – the primary ring – is used for data transfer. The other ring – the secondary ring – is usually a backup, but it too can carry data, increasing the transfer rate to 200 Mbps. FDDI was widely used in campus networks, but once again, was surpassed by the emergence of the Gigabit Ethernet. However, FDDI is a good choice as a network backbone for an Ethernet network. Wireless networks do not require any cabling to operate, and the standards governing such networks are overseen by the IEEE (category 802.11 and subsequent revisions). Such networks may use the following kinds of signals to communicate:   

infrared high-frequency radio waves microwave

infrared Infrared is used in confined areas, as line of sight communication is required. Infrared cannot penetrate buildings, but can bounce off reflective surfaces in the same way as signals from a TV remote control. high-frequency radio waves Wireless networks can use high-frequency radio waves to connect computers in a network. These connections use a network interface card (NIC) that can send and receive signals using an antenna. High-frequency radio wave signals can travel through buildings, but are subject to interference. microwave Because microwave signals are commonly used for satellite communication, it is no surprise that they can also be used in a wireless network. However, adverse weather conditions such as fog can interfere with microwave signals.

A common configuration for a wireless network includes a number of access points connected to a wired LAN. Mobile users can connect to the LAN provided that they are within the footprint extended by the access point.

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Summary A network can be defined as a group of devices connected in such a way that they can share data and resources. Two types of networks – client/server networks and peer-to-peer networks – are controlled in different ways. A client/server network consists of one or more central computers known as servers, to which the other computers connect as clients. In a peer-to-peer network adjacent computers connect to each other, and there is no central point of control. A network topology is the physical or logical layout of its components. A logical topology defines how network components connect, whereas a physical topology defines how the network actually looks. Common network topologies are bus, mesh, ring, and star. Ethernet – as defined in the International Electrical and Electronic Association (IEEE) standard 802.3 – is the most commonly used networking technology used in LANs worldwide. It uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol, and originally had a data transfer rate of 10 Mbps. Later versions, such as the Fast Ethernet and the Gigabit Ethernet, increased this to 100 and 1000 Mbps respectively. Token Ring is a networking technology that allows only one node at a time to transmit data. Such a network is arranged in a physical star topology but operates as a logical ring. A Fiber distributed data interface (FDDI) network is similar to a Token Ring network. Wireless networks do not require any cabling to operate, and can use different kinds of signal to communicate.

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Network protocols and MAC/IP addressing

1. Defining network protocols The data transfer process in any network can be broken down into a number of different stages or categories, and these categories are placed in a layered sequence based on their relationship to the user. So the highest layer would be the application, with which the user interacts. The layer, or layers, beneath this would be the domain of the operating system (OS), and the lowest layer would be the actual physical network, over which the data is transferred.

Note The Open Systems Interconnection (OSI) model defines seven layers, beginning, at the top, with Application (Layer 7), Presentation (Layer 6), Session (Layer 5), Transport (Layer 4), Network (Layer 3), Data Link (Layer 2), and finally Physical (Layer 1) layers. Each level uses a different method to address a computer or device on a network. So the applications using the network – a web browser, for example – may use the port addresses (port 80 for HTTP traffic). The OS supports the networking protocols, which use addresses such as the host name or IP address. The physical layer would use a hardware address, such as the media access control (MAC) address. Network protocols at the OS level include   

Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) NetBIOS Extended User Interface (NetBEUI) Transmission Control Protocol/Internet Protocol (TCP/IP)

Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) IPX/SPX is a pair of network protocols used in Novell NetWare OSs. These are considered to be legacy protocols and cannot be used on the Internet. NWLink IPX/SPX-Compatible Transport, or NWLink is Microsoft's 32-bit version of IPX/SPX for the Windows NT, Windows 2000, Windows XP, and Windows .NET Server platforms. NetBIOS Extended User Interface (NetBEUI) NetBEUI is a networking protocol developed by IBM and Microsoft, which is supported by most Windows platforms. Because NetBEUI does not allow routing between networks, it is not supported on the Internet. It is, however, faster than TCP/IP. Transmission Control Protocol/Internet Protocol (TCP/IP) TCP/IP refers to the suite of networking protocols used on the Internet. It's the standard protocol suite for data transmission between networks, and its wide acceptance means it is supported by virtually all OSs, including Windows, Linux, Macintosh, and UNIX.

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To use a network protocol, you first have to install a network interface card (NIC) on a computer so that it can connect to a network. After installing the NIC, you connect the network cable to a network device – a hub for example. Once you've connected the network cable, you install the network protocol – TCP/IP for example – on the OS. The network protocol then associates itself with other components of the OS in a process called binding, which allows the NIC to use the network protocol to transfer data over the network. You can check which network protocols are installed in Windows by viewing the properties of a particular network connection. Suppose that you want to determine which protocols are installed on a Windows 2000 machine, and you have opened the Control Panel. To do this, you double-click the Network and Dial-up Connections icon. In the Network and Dial-up Connections window, you click the Local Area Connection icon. Then you select File - Properties. The Local Area Connection Properties dialog box displays information about the type of NIC, or network adapter, the machine is using, and the components that are bound to this adapter. In this example, the TCP/IP network protocol is bound to this adapter.

2. Addressing on a network Each device and application on a network has a unique address, which the network uses to identify it. Networks use the following methods to identify devices and applications:    

port addresses character-based names IP addresses media access control (MAC) addresses

port addresses A port address is a number between 0 and 65,535 that identifies an application or service on a computer in a TCP/IP network. For example, a client in such a network can access a web server with HTTP using the port address 80. character-based names Character-based names are names that identify a computer on a network using letters. They include domain names (cheryl.sales.imagenie.com for example), host names (cheryl), and Network Basic Input / Output System (NetBIOS) names (CHERYL). Host names and NetBIOS names are often referred to as computer names. IP addresses An IP address is a 32-bit address that identifies a device on a TCP/IP network, such as the Internet. IP addresses are expressed in the dotted quad notation, in which each byte of the address is

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expressed in decimal notation. This simply makes the address easier to read. An example of an IP address is 192.50.20.1. The first byte of this address is the binary equivalent of 192 (11000000). media access control (MAC) addresses A MAC address is a unique 6-byte address that identifies a node in an Ethernet network. It is also known as a hardware address, Ethernet address, or physical address. In a PC, the MAC address is assigned to the NIC, where it is almost always hard coded into a ROM chip on the card. In some cases, you may be able to change the MAC address, although this is not a good idea. MAC addresses are expressed as a series of six pairs of hexadecimal numbers separated by hyphens. An example of a MAC address is 00-D0-B7-54-54-98.

MAC addresses are used at the physical network level to allow computers on the same LAN to communicate. A host uses the operating system to find the MAC address of another host on the same network. Computers on different networks cannot use MAC addresses for communication because the hardware protocol (Ethernet) controls traffic only in its own LAN. So computers on different LANs use IP addresses to communicate across the Internet. Suppose that you want to display the IP address and the NIC's MAC address on a Windows 98 machine. To do this, you first access the Run dialog box. You select Start - Run. Alternatively, you press Alt+S+R. In the Run dialog box, you enter the command to open the IP configuration dialog box. You type winipcfg in the Open text box and click OK. Alternatively, you type winipcfg and press Enter. The IP Configuration dialog box displays general information about the network adapter, or NIC. In this case, it is displaying information about the point-to-point protocol (PPP) adapter. You want to display information for the NIC, which is bound to TCP/IP. You select Realtek RTL8139/810x from the drop-down list. The IP Configuration dialog box now displays the MAC address – or the adapter address – of the NIC and the IP address. Suppose that you now want to display the NIC's MAC address and the IP address on a Windows 2000 machine.

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You select Start - Programs - Accessories - Command Prompt. Alternatively, you press Ctrl+Esc and then select Programs - Accessories Command Prompt. At the command prompt, you enter the command that displays the IP address and the MAC address of the NIC. You type ipconfig/all and press Enter. The ipconfig command, with the /all option, displays the current IP configuration for the network, the MAC address – or physical address, and the IP address. This command can be used in Windows XP and Windows NT also. After viewing the information, you type exit at the command prompt to exit the command prompt window.

3. IP addresses and their characteristics An IP address is a 32-bit address that identifies a device on an network using TCP/IP, such as the Internet. IP addresses are expressed in the dotted quad notation, in which each byte, or octet, of the address is expressed in decimal notation. In this notation, each octet can be a number from 0 to 255, because the largest possible 8-bit number is 11111111 – which is 255 in decimal. An IP address is divided into the following two parts:  

Network Host

Network The network portion of the IP address identifies the network on which a device is located. This allows the routing of data over interconnected networks. Host The host portion of the IP address uniquely identifies a host, or node, on a network. This allows the routing of data to the correct node once it arrives at the local network.

IP addresses are divided into the following classes, based on the number of host addresses they make available to a network.   

Class A Class B Class C

Class A

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A Class A IP address uses the first octet for the network address, which is a number between 0 and 126. It uses the last three octets for the host address, but as with all classes of IP address, the last octet of the host address cannot have 0 or 255 as a value. A single Class A address can support about 16 million host addresses. An example of a Class A address is 87.0.0.1. Class B A Class B IP address uses the first two octets for the network address, and the last two octets for the host address. The first octet is a number between 128 and 191, and the second octet is a number between 0 and 255. A Class B address can have about 65,000 host addresses. An example of a Class B address is 135.18.0.2. Class C A Class C address uses the first three octets for the network address, and the last octet for the host address. The first octet is a number between 192 and 223. A Class C address can only have 254 host addresses, because you cannot use the values 0 or 255 for the last octet. An example of a Class C address is 200.80.15.1.

Each IP address class uses a specific range of network octets and each class supports a different number of network licenses and IP addresses.

Classes of IP addresses Class Network Octets

Total Number of Possible Networks for Licenses

Host Octets

Total Number of Possible IP Addresses in Each Network

A

0._._._ to 126._._._

127

_.0.0.1 to _.255.255.254

Approximately 16 million

B

128.0._._ to 191.155._._

16,000

_._.0.1 to _._.255.254

Approximately 65,000

C

192.0.0._ to 223.255.255._

2,000,000

_._._.1 to _._._.254

254

There are two other classes of IP address – D and E – that are not available for general use. This class-based system is wasteful because it leaves too many unused IP addresses – even the largest corporations are unlikely to use or require the 65,000 host addresses in a Class B network. For this and other reasons, the class-based system is being replaced by a mechanism known as classless interdomain routing (CIDR), in which the network and host are assigned an arbitrary number of bits – rather than just 8, 16, or 24 bits as in the old system. An IP address using CIDR is followed by a slash and then a number, indicating how many bits of the address are reserved for the network. For example, the 28 after the slash in the address 172.26.1.32/28 indicates that 28 bits in this address are reserved for the network, leaving four bits for the host. This means such a network could accommodate 14 hosts (2 to the power of four, minus two addresses which are reserved). Assigning

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this address to a small company with 12 employees is obviously more efficient than assigning the company a Class C address, with 254 possible host addresses. Summary A layered model for communication over a network can be constructed, consisting of an application layer, an operating system (OS) layer, and a physical layer. Network protocols operate at the OS layer, including Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX), NetBIOS Extended User Interface (NetBEUI), and the standard Internet protocol, Transmission Control Protocol/Internet Protocol (TCP/IP). Devices or applications on a network can be identified using a character-based name, IP address, media access control (MAC) address, or a port address. Computers use MAC addresses to communicate with other computers on the same LAN, whereas computers on different LANs use IP addresses to communicate, across the Internet for example. An IP address is a 32-bit address that identifies a device on the Internet, and consists of two parts – a network and a host address. IP addresses can be divided into three classes – Class A, Class B, and Class C – based on the number of host addresses they support.

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Installing and configuring network cards

1. Installing a NIC To connect a computer to a network via cable, you need to install a network interface card (NIC) and use network cable to attach the computer to a network device, such as a hub. To use a wireless connection, you need to install a wireless NIC. This type of NIC performs exactly the same function, but is more likely to be used in a mobile PC such as a notebook. Installing a NIC involves the following steps:   

inserting the NIC and installing its drivers configuring the NIC testing the NIC

inserting the NIC and installing its drivers Before installing a NIC, you may have to configure the dip switches or jumpers on the card. Most modern cards are Plug and Play (PnP) compatible, however, so you don't generally need to do this. You attach the NIC directly into the appropriate slot – the Peripheral Component Interconnect (PCI) slot, for example – on the motherboard. Then you turn on the computer, and the operating system (OS) detects the NIC and allows you install the NIC's drivers. You should choose to load these drivers from the manufacturer's disks, which are provided with the card, rather than using the Windows drivers. After you have completed this process, you should verify that the NIC is installed correctly, with no conflicts or errors. configuring the NIC After the card has been installed and its drivers loaded correctly, you must configure the NIC so that it can access the network you wish to connect to. The way in which you do this will depend on the OS installed and on the kind of network protocols that are in use. testing the NIC You can test the NIC by using different OS utilities to check for the presence of the other computers in the network.

In Windows XP, when you have installed the NIC and its drivers, you should check that the card is installed correctly. To do this, you use either the Device Manager or the Control Panel to access the properties of the NIC. To use the Device Manager to do this, you select the NIC, right click, and select the Properties option. To access the properties of a NIC in Windows XP from the Control Panel, you first double-click the Network Connections icon.

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The Network Connections window displays an icon for the local network connection, which you can use to view the properties of the NIC. You click the Local Area Connection icon. You select File - Properties. Alternatively, you press Alt+F+R. The General tabbed page of the Local Area Connection Properties dialog box provides the name of the NIC and the software and protocols it is configured to use. From this page, you can access the Properties dialog box for the NIC. You click the Configure button. Alternatively, you press Alt+C. The Properties dialog box – in this case for a Realtek RTL8139 Family PCI Fast Ethernet NIC – provides general information about the network card. The general information includes the type of device, the manufacturer, and the location of the device. It also displays the status of the device. In this case, the device has been installed correctly and is working properly. To view the properties of a NIC using Windows 2000, you perform the following steps:   

from the Control Panel, open the Network and Dial-up Connections window select Local Area Connection access the properties for the connection

2. Assigning a computer name After you've successfully installed a NIC on a computer, you're ready to connect to the network. The protocol that the network uses must be installed on your OS, so as to automatically bind it to the NIC. For example, if you want to connect to a Windows 2000 or Windows XP PC to a network that uses NetBEUI, you must install this protocol first. Then you assign a computer name to your computer to identify it on the network. Computer names can have up to 15 characters, and contain a series of letters and numbers, but no special characters. You change the default computer name for a Windows 2000 and a Windows XP computer through the Control Panel. Suppose that you want to change the default computer name for a Windows 2000 computer. You double-click the System icon. The General tabbed page of the System Properties dialog box displays general information about Windows 2000. You click the Network Identification tab.

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The Network Identification tabbed page displays the current name of the computer, and the name of the workgroup to which it belongs. These may have been assigned during the Windows 2000 setup process, and they can be changed. You click the Network ID button to use a wizard to join the computer to a domain and to create a local user. Or – as in this case – you can choose to do this manually. You click the Properties button. The Identification Changes dialog box allows you to change the name of the computer, as well the domain or workgroup to which it belongs. In this case, you want to change the name of the computer to "PC1", but decide not to change the workgroup name or domain – if you want to change these settings you must ask your network administrator first. You type PC1 in the Computer name text box and click OK. The Network Identification message box informs you that you must reboot the computer for the change to take effect. You click OK. The Network Identification tabbed page displays the new computer name, and informs you that the change will only take effect once you restart the computer. And you click OK to close the System Properties dialog box. To change the name of a computer to PC1 in Windows XP, you perform the following steps:   

open the System Properties dialog box access the computer name enter a new name

3. Installing and configuring TCP/IP As the TCP/IP protocol is the protocol used on the Internet, it is installed by default when you install a NIC in Windows 2000 or Windows XP. If problems occur or TCP/IP has been uninstalled, you may need to install this protocol again. Provided TCP/IP is installed, you can alter its properties to specify the IP and domain name system (DNS) server addresses used by a computer. Suppose that you want to set the properties of the TCP/IP protocol in Windows XP. In the Control Panel, you first double-click the Network Connections icon. From the Network Connections window, you can access the properties of the local network connection for which you need to configure TCP/IP. Click the Local Area Connection icon, and select File - Properties. Alternatively, you click the Local Area Connection icon and press Alt+F+R. The General tabbed page of the Local Area Connection Properties dialog box identifies the connection and the components that it uses – including TCP/IP. You select Internet Protocol (TCP/IP) and click the Properties button.

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The Internet Protocols (TCP/IP) Properties dialog box allows you to choose how the IP and DNS addresses are assigned. Suppose you are currently using fixed, or static, IP addresses, but your network administrator has advised you that these addresses can be obtained automatically, so you have to change your settings. You select the Obtain an IP address automatically and the Obtain DNS server address automatically radio buttons, and click OK. You've now changed the properties of the TCP/IP protocol on a Windows XP computer. To change the properties of TCP/IP in Windows 2000, you perform the following steps:    

open the Network and Dial-up Connections window access the properties of the local network connection access the properties of TCP/IP change the settings

Summary To connect a computer to a network, you install a network interface card (NIC) for it. This involves attaching the NIC to the computer, configuring the NIC, and testing that it is functioning correctly. Once you've connected a computer to a network, you can change the default computer name. Computer names can have up to 15 characters, containing a series of letters and numbers. When you install a NIC in a Windows 2000 or a Windows XP computer, the Transmission Control Protocol/Internet Protocol (TCP/IP) installs by default. You can reinstall it if necessary however. You configure the properties of TCP/IP to specify the IP address and domain name system (DNS) address for a computer, or to specify that these addresses are obtained automatically.

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Internet connectivity Introduction Networks use devices and specific bandwidth technologies to connect to other networks.

Routers Many computer users focus on the technologies that operate within a single Local Area Network (LAN). Of course, there must be a way for data to be transferred between LANs, so as to create the network of computer networks that is the Internet. A router is the key piece of hardware in the Internet, as it acts – strictly – as an interface between two computer networks.

A router

Routers allow data to be transferred or routed between networks. They can do this in the most efficient way possible, to networks far removed from the LAN in which the data originated. When using the Transmission Control Protocol/Internet Protocol (TCP/IP), routers use IP addresses to determine the path to a destination. Devices such as switches and bridges, on the other hand, use media access control (MAC) addresses to determine the correct path to a destination. A router is known as a stateless device because it handles the destination address of the data that it routes rather than the data itself. A router creates and maintains a table of all the available routes in the networks to which it is connected. When a router receives a packet, it first checks the destination IP address of the packet. It then uses the table to determine the most efficient, available routing path for the packet. The entries in the table can be inputted manually or dynamically maintained. If the router fails to find a good route, it may forward the packet to another router or drop the packet altogether. The way in which the router treats different packets can be specified by a network administrator.

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Routers in different networks

Routers can be connected to several networks, and can route traffic to and from the networks to which they are connected. So for example, router A in the figure above, which is connected to a client PC, may belong to one network, whereas router B, connected to a server, belongs to another network. Data flows to and from the client PC via the intermediate routers, which belong to different networks, although some routers (1 and 2, or 3 and 4) belong to the same network. The exact path taken between routers A and B will depend on many factors, such as the amount of network traffic. In fact, if a chunk of data at B is divided into several packets and sent to A, each packet may take a different route. The chunk of data can be reassembled from the packets at B and presented to the application that requires it. Data can only be routed to remote networks in this way if the protocol used to produce the data is a routable protocol. TCP/IP and Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) for example, are routable protocols, whereas NetBios Extended User Interface (NetBEUI) is not.

Brouters A brouter is device that functions both as a network bridge and as a router. A brouter can route TCP/IP and IPX/SPX packets to remote networks, as a router can do, as these are routable protocols. However a brouter can also handle other traffic, such as NetBEUI packets, in the same way that a bridge would.

Communication technologies Bandwidth In analog systems, bandwidth is the difference between the highest-frequency and the lowest-frequency signal components of a transmission channel. Frequency is measured as the number of cycles per second, or Hertz (Hz). In digital systems, bandwidth indicates the data transmission in bits per second

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(bps), and the standard prefixes are used to indicate values such as a thousand bps (Kbps), a million bps (Mbps) and a billion bps (Gbps). So bandwidth is a measure of the amount of data that can travel over a communication system in an allotted time frame. It may be referred to as data throughput or line speed. Bandwidth is directly proportional to the rate of communication, meaning that the greater the bandwidth, the faster the communication.

Common communications technologies There is a wide range of networking technologies in use today. These include cable modems, digital subscriber line (DSL), Integrated Services Digital Network (ISDN), regular telephone lines, satellite connections, and wireless connections.

Cable modem A cable modem is a modem that allows a PC to access the Internet using a cable television connection. A cable modem is always connected and is an example of a broadband medium. A broadband medium carries multiple types of transmissions. When a PC transmits digital signals, the cable modem converts the digital signals to analog signals, and it converts any incoming analog signals back to digital signals.

Digital subscriber line (DSL) DSL is a broadband digital technology that uses regular copper phone lines to transmit and receive data. DSL uses different frequencies to those of voice, allowing you to use the same phone line for voice and data transmissions at the same time. DSL is always connected.

Integrated Services Digital Network (ISDN) ISDN is a broadband technology that uses normal telephone lines or digital telephone lines to send data, video, and voice. Users can access an ISDN via dial-up connections. An ISDN line consists of two channels on a single pair of wires, called B channels, which can separately support speeds up to 64 Kbps. These channels can be combined to give an effective bandwidth of 128 Kbps. An ISDN line also consists of a slower control channel, called the D channel.

Regular telephone lines Regular telephone lines are a common way to connect to an Internet service provider (ISP), using an internal or external modem that converts digital data to analog data. This modem is necessary as regular telephone lines can only transmit analog data. Typically, such lines offer a maximum possible bandwidth of 56 Kbps, but, on average, the actual value is likely to be half this. This is too slow even for most home users, which is the main reason why technologies such as ISDN are increasingly popular.

Satellite access Satellite access provides high-speed Internet connections and is useful in remote areas, in which other types of connections aren't possible. Unlike cable modems and DSL, satellite access is available from almost anywhere. In a typical scenario, a satellite dish – mounted on top of a building – exchanges data with an orbiting satellite, the use of which is offered by an ISP.

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Wireless access Wireless access refers to systems and devices that don't require cables to communicate with other devices. Wireless access is useful for mobile devices – such as cellular phones – and for Internet access in remote locations, where wired transmission is impossible. Wireless access is not as common as wired data transmission because it can be expensive, and may be prone to environmental factors to which wired communication is immune. These and other communication (or networking) technologies, together with the maximum bandwidth available, are listed in this table.

Bandwidth technologies Technology

Maximum Bandwidth

Common Uses

Asymmetric digital subscriber line (ADSL)

640 Kbps upstream and up to 6.1 Mbps downstream

Home users who require fast download speeds, but are not so concerned about upload speeds, as most of the bandwidth is from the ISP to the user

Asynchronous transfer mode (ATM)

25, 45, 155 or 622 Mbps

Used in LAN backbones

Cable modem

512 Kbps to 5 Mbps

Most suited for connection between a home or small business and an ISP

Ethernet

10 Mbps to 1 Gbps

Most popular technology for LANs. Original Ethernet specification supported 10 Mbps, later versions are the Fast Ethernet (100 Mbps) and Gigabit Ethernet (1 Gbps). The 10 Gigabit Ethernet (10GbE) is in development

Fiber distributed data interface (FDDI)

100 Mbps

A good choice for a LAN backbone

Fractional T1

The number of channels of the T1 leased times 64 Kbps but less than full T1 (1.544 Mbps)

Enterprises who do not need the bandwidth of a full T1 line

Frame relay

56 Kbps to 45 Mbps

Corporate WANs – for businesses that need to communicate internationally

G.Lite (also known as DSL Lite)

From 1.544 to 6 Mbps (upstream) and 128 to 384 Kbps (downstream)

A popular version of DSL for home users because it does not require a visit from the telephone company to configure the connection

GSM mobile telephone service

9.6 to 14.4 Kbps

Wireless technology used for mobile telephones

High-bit-rate DSL (HDSL)

Up to 3 Mbps

Symmetric (equal upstream and downstream bandwidths) DSL technology, used to provide dedicated WAN links for businesses

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Bandwidth technologies Technology

Maximum Bandwidth

Common Uses

Institute of Electrical and Electronics Engineers (IEEE) 802.11b (wireless)

5.5 Mbps or 11 Mbps

A popular wireless technology, widely used in wireless LANs (WLANs)

IEEE 802.11a (wireless)

Up to 54 Mbps

Considered as the successor to 802.11b, but incompatible with it

Integrated services digital network DSL (IDSL)

128 Kbps

Home users who cannot use ADSL or HDSL

Integrated services digital network (ISDN)

64 Kbps to 128 Kbps

Home users and small enterprises

Regular telephone (POTS, plain old telephone service)

Up to 56 Kbps

Uses a modem to connect a home to an ISP

Synchronous optical network (SONET)

51, 155, 622, 1244, or 2480 Mbps

Most suited for backbones, different set of SONET signaling rates represented by optical carrier (OC) levels, ranging from OC-1 (52 Mbps) to OC-256 (9.6 Gbps)

T1

1.544 Mbps

Connections between large companies and branch offices or an ISP

T3

45 Mbps

Corporations that transmit large amounts of data, and require the increased bandwidth

Token Ring

4 or 16 Mbps

Most suited for LANs, but eclipsed by Ethernet, considered a legacy technology

Very-high-rate DSL (VDSL)

Up to 55 Mbps (upstream) and 2.3 Mbps (downstream) over short distances (less than a mile)

Emerging DSL technology

X.25

Up to 2 Mbps, but typically 64 Kbps

Communication between mainframes and "dumb" client terminals, largely replaced by other technologies, but still used in specialist financial applications

Summary

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A router is a device that acts as an interface between two computer networks. These devices transmit data across connecting networks to forward a message to its destination using the most efficient, available route. Routers create and maintain tables that list all the available routes on a network. A brouter is a device that combines the function of network bridge and a router. It can route packets to remote networks as a router can do, provided these packets are transferred using a routable protocol. A brouter can also handle other traffic in the same way that a bridge would. So bandwidth is a measure of the amount of data that can travel over a communication system in an allotted time frame. There are various kinds of communication and networking technologies used today. The most common technologies include the cable modem, digital subscriber line (DSL), Integrated Services Digital Network (ISDN), regular telephone lines, satellite access, and wireless access.

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System Resources and Installing and Configuring IDE and SCSI Devices

IRQ, DMA, and I/O ports 1. Transferring data The most common operation that users perform on PCs involves moving information from one location to another. To move information, you need to allocate system resources – interrupt request (IRQ) channels, I/O addresses, and direct memory access (DMA) channels – to the system's hardware devices. For a hardware device to work with the system's microprocessor, it needs an address so that the system can find it. The system therefore sets aside large amounts of addresses for use by input and output devices. Standard I/O ports include traditional and new standard ports. Traditional standard ports include    

Keyboard ports Parallel ports RS-232C serial ports Game ports

Keyboard ports A PC has a keyboard port connected directly to the motherboard. The traditional AT style keyboard connector is quickly being replaced by the smaller PS/2 keyboard connector. Parallel ports Parallel ports are 25-pin female, D-shaped sockets. The port is distinctive in that it has wire wings that lock the plug to the socket. RS-232C serial ports Serial ports – similar in shape to parallel ports – support two types of connectors – the 25-pin Dtype connector (DB-25) and a 9-pin D-type connector (DB-9). Game ports Game ports are 15-pin connectors. They are used largely to attach game devices such as a joystick to a PC.

New standard ports include     

PS/2 mouse and keyboard ports universal serial bus (USB) ports IEEE-1394 FireWire ports infrared ports improved parallel ports

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PS/2 mouse and keyboard ports The smaller mini-DIN PS/2-style port is a new standard port for the keyboard and mouse. PCs that use the mini-DIN for both the keyboard and mouse include a clear mark on each socket to indicate its use. The mini-DIN port is a round, 6-pin socket. universal serial bus (USB) ports USB is a general-purpose connection to which you can connect up to 127 USB devices – including, for instance, a mouse, keyboard, scanner, and camera. The port is a distinctive rectangular shape. IEEE-1394 FireWire ports IEEE-1394 FireWire ports are 4-pin or 6-pin sockets used to connect devices such as digital video cameras to a PC. The 6-pin connection provides power as well as data transfer, but the 4-pin connection uses a separate power supply. Most PCs do not have built-in FireWire ports, so you need to purchase a FireWire adapter card to use one. infrared ports Infrared ports enable you to transfer data – via infrared light waves – from one device to another without the use of cables. The port is usually a small, black, opaque window. improved parallel ports Parallel ports are 25-pin, D-shaped sockets, mostly used to connect printers to PCs.

A connection can transfer information in one of the following modes:  

parallel serial

parallel In parallel mode, a set of parallel conductors transfers an entire word at a time. A transfer in parallel mode needs one clock pulse. serial In serial mode, bits of a word are sent along a single conductor, one at a time. Serial transfers take longer to complete than parallel transfers because each bit requires a clock cycle to transfer.

While a program is executing, a microprocessor reads from and writes to memory locations. The microprocessor can also read from or write to one of the system's I/O devices. Whether a peripheral device has a serial or parallel connection, the following methods can initiate data transfer between the system and the device:    

DMA interrupt-driven I/O polling programmed I/O

DMA Using the DMA method, a peripheral device takes control of the system's buses to conduct direct transfers. A DMA channel can be thought of as a shortcut for information to move between a device and memory. interrupt-driven I/O Using the interrupt-driven I/O method, a peripheral device tells the microprocessor that it is ready to transfer information via a line of the motherboard bus. polling

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Using the polling method, the microprocessor checks the status of the peripheral device under program control. It does this using software to determine whether a device is ready to transfer information. programmed I/O Using the programmed I/O method, the microprocessor sends a command to a peripheral device by applying the device's address to the system's address bus. If a device is in use, it delays information transfer.

Using the interrupt-driven I/O method, certain I/O devices – such as the keyboard and disk drives – sometimes require services from the microprocessor. Because this can occur at any time, I/O devices can interrupt the microprocessor to receive attention. They do this by issuing an interrupt signal to the microprocessor's interrupt controller. The microprocessor stops its current operation, completes the service, and then returns to the operation on which it was working. Every device that has the ability to interrupt the microprocessor must have a unique IRQ number. The system uses this number to identify the device that needs a service. Microcomputers use the following types of interrupt signals:  

Maskable Interrupts (IRQs) Non-Maskable Interrupts (NMI)

Maskable Interrupts (IRQs) IRQs are interrupts that the system microprocessor can ignore under certain circumstances. Some IRQ lines have a higher priority than others and therefore receive attention first. Non-Maskable Interrupts (NMI) NMIs are critical interrupts to which the microprocessor must always react. They can cause the system to shut down without storing any potentially bad data. The system board sends an NMI signal to the microprocessor if an adapter card in one of the board's expansion slots sends an active IO Channel Check (IOCHCK) signal a parity check (PCK) error occurs in the system's dynamic RAM (DRAM) memory

Sixteen interrupt channels – IRQ0 to IRQ15 – are available. Three of these are normally located inside the system board's chipset and therefore do not have external IRQ pins. The remaining channels handle interrupt functions based on the needs of the user. If more than one IRQ is requested at the same time, the interrupt controller selects the IRQ that has the lowest value and processes it first. For example, a keystroke will be processed before a mouse click because the keyboard uses IRQ 1 and the mouse uses IRQ 12. With the introduction of the 16- bit bus, more IRQs – 8 to 15 – were introduced and as a result a second interrupt controller. The second interrupt controller communicates with the CPU via the first interrupt controller. It initially used IRQ 2 to signal the first controller but certain devices were already using IRQ 2, so the new IRQ 9 was tied to the IRQ 2 pin. This means that a device can still use the pin for IRQ 2 but it's really using IRQ 9. This resulted in the IRQ priority level being as follows:

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0,1,8,9,10,11,12,13,14,15,3,4,5,6,7

Interrupt request channels System interrupt levels Interrupt Name

Description

Interrupt Name

Description

IRQ0

Timer/counter alarm

IRQ8

Real-time clock

IRQ1

Keyboard buffer full

IRQ9

Cascade to INTC1

IRQ2

Cascade from INTC2

IRQ10

Spare

IRQ3

Serial port 2 (COM 2 or 4)

IRQ11

Spare

IRQ4

Serial port 1 (COM 1or 3)

IRQ12

Spare PS/2 mouse

IRQ5

Parallel port 2

IRQ13

Coprocessor

IRQ6

Floppy disk drive (FDD) controller

IRQ14

Primary Integrated Drive Electronics (IDE) controller

IRQ7

Parallel port 1 – line printer terminal 1 (LPT1)

IRQ15

Secondary IDE controller

DMA operations are similar to interrupt-driven I/O operations, but the microprocessor does not need to stop its operation to provide service to a device. A DMA controller requests that the microprocessor allow it control over the system to complete an I/O transfer. DMA controllers are specialized controllers that perform transfers much more quickly than standard microprocessors.

Available DMA channels

DMA channel designations Channel Name

Function

DMA Controller

Page register address

CH0

Spare – any of the spare channels can be used by the newer parallel port modes

1

0087

CH1

Synchronous Data Link Control (SDLC) ( Network

1

0083

CH2

Floppy disk drive (FDD) controller – uses channel 2 by default

1

0082

CH3

Spare

1

0081

CH4

Used internally to cascade the two, fourchannel DMA controllers

2

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DMA channel designations Channel Name

Function

DMA Controller

Page register address

CH5

Spare

2

008B

CH6

Spare

2

0089

CH7

Spare

2

008A

2. Onboard and system I/O methods Two forms of I/O devices exist – the system board's onboard I/O devices and the peripheral devices that work with the system via its expansion slots. Most I/O functions have become standardized. As a result, integrated circuit (IC) manufacturers produce them in single-chip application-specific integrated circuit (ASIC) formats. Some I/O connections – such as the system's parallel printer ports, RS-232 serial ports, and game ports – have also become standardized on certain PCs. For I/O functions and I/O connections, the I/O controllers incorporated into the ASIC govern the matching of signal levels and protocols between a computer system and I/O devices. By using I/O addresses, the system can communicate with its onboard intelligent devices. The system does this by using the onboard address decoder, which converts addresses from the address bus into enabling bits for the system's intelligent devices. Computers handle addresses differently according to whether they are classed in software as memory or I/O addresses. Addresses are located in the overall I/O addressing map of the system. In a PC-compatible system, standard I/O adapters use I/O port addresses. The devices with I/O port addresses are identified according to their usage as system or I/O devices. For example, the I/O port address for a game port is 200207 and the device is classed as an I/O device.

Interrupt vectors I/O port addresses Address

Device

Use

000-01F

DMA controller

System

020-03F

Interrupt controller

System

040-05F

Timer/Counter

System

060-06F

Keyboard controller

System

070-07F

Real-time clock, NMI mask

System

210

I/O port addresses Address

Device

Use

080-09F

DMA page register

System

0A0-0BF

Interrupt controller

System

0F0

Clear math coprocessor busy

System

0F1

Reset math coprocessor

System

0F8-0FF

Math coprocessor

System

170-177

Second IDE controller

I/O

1F0-1F7

First IDE controller

I/O

200-207

Game port

I/O

278-27F

Parallel printer port #2

I/O

2F8-2FF

Serial port #2

I/O

378-37F

Parallel printer port #1

I/O

3B0-3BF

MGA/first printer port

I/O

3D0-3DF

CGA

I/O

3F0-3F7

FDD controller

I/O

3F8-3FF

Serial port #1

I/O

FF80-FF9F

USB controller

I/O

Memory addresses incorporate the system's I/O port addresses – 0 to 3FF – and include other addresses used for different functions. For example, the memory address for Program Memory is 600-9FFFF.

Memory address map System memory addresses Address

Function

0-3FF

Interrupt vectors

400-47F

ROM-BIOS RAM

480-5FF

Basic and special system function RAM

600-9FFFF

Program memory

0A00000AFFFF

Video Graphics Adapter (VGA)/Enhanced Graphics Adapter (EGA) display memory

0B00000B0FFF

Monochrome display adapter memory

0B80000BFFFF

Color graphics adapter memory

0C00000C7FFF

VGA/Super Video Graphics Adapter (SVGA) BIOS

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System memory addresses Address

Function

0C80000CBFFF

Enhanced Integrated Drive Electronics (EIDE)/Small Computer System Interface (SCSI) ROM, and older hard disk types

0D00000D7FFF

BIOS extension area ROM

0D00000DFFFF

LAN adapter ROM

0E00000E7FFF

BIOS extension area ROM

0E80000EFFFF

BIOS extension area ROM

0F00000EFFFF

BIOS extension area ROM

0F40000EFFFF

BIOS extension area ROM

0F80000EFFFF

BIOS extension area ROM

0FC0000FDFFF

ROM BIOS

0FE0000FFFFF

ROM BIOS

3. Typical IRQ and I/O assignments I/O addresses are port addresses that the CPU uses to locate hardware devices. Computer devices use IRQs to signal the CPU that they require services. Most new system boards contain Floppy Disk Controller (FDC) circuitry and a physical interface connection to a floppy drive disk (FDD). The following components connect via a floppy drive cable:  

FDC FDD

FDC The FDC provides a programmable, logical interface for up to two FDD units. Its I/O address range is between 3F0 and 3F7and its IRQ is 6. FDD An FDD connects to a 34-pin flat ribbon cable, which in turn connects to the system board's FDD interface. The FDC divides an FDD into 80 tracks per side, with 9 or 18 512-byte sectors per side. This

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means that the system either has 720 kilobytes (KB) or 1.44 megabytes (MB) of total storage on each disk. Its I/O address range is 3F0 to 3F7 and it has an IRQ value of 6.

The FDC functions by receiving and decoding instructions from the system to the floppy disk drive at addresses within the address range 3F0-3F7h. It decodes these commands and creates the correct signals to prompt their execution. It then converts the data from the system's parallel format to the encoded serial format that the disk drive uses. The FDC operates with the DMA controller of the system. It is assigned to the DRQ-2 and DACK-2 lines. During operation, for every byte of data that must be transferred, the FDC sends a DRQ-2 signal to the DMA controller. Once the last byte is transferred, the system generates an FDC interrupt. Every time the system sends a read, write, or format command, it creates an interrupt signal. Either one or two Enhanced Integrated Drive Electronics (EIDE) controllers – a primary controller and a secondary controller – host the HDD. Each controller can handle up to two IDE drives, which means that the PC can control up to four IDE devices. The first IDE drive at each connector is called the master drive. A second drive acts as a slave. The settings of configuration jumpers on each drive determine whether it is the master or the slave drive. A drive attached to the host connector as the only unit can be configured as a single drive. The system board provides two 40-pin connectors – IDE1 and IDE2 – each labeled according to the IDE controller to which it corresponds. IDE1 is assigned IRQ 14, whereas IDE2 has an IRQ of 15. The following types of ports are controlled in the CMOS:  

USB Infrared

USB Most ATX system boards come with dual USB connectors. The I/O address of an onboard USB controller is between FF80 and FF9Fh. PnP assigns an IRQ to the USB controller. Via the CMOS Setup Utilities, you can enable the USB function and assign IRQ channels to ports. If no USB device is used, you should set the IRQ allocation to not applicable (NA) to free up the IRQ. Infrared Infrared Data Association (IrDA) ports offer short-distance wireless connections for a range of IrDA-compliant devices like printers and personal digital assistants (PDAs). They are therefore popular with notebook computer users. IrDA ports communicate by sending and receiving a serial stream of light pulses. The infrared port is therefore assigned the same system resources as those given to COM2/COM4 – serial port #2

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– serial ports. Its IRQ is therefore 3 and its I/O address range is either 2F8 to 2FFh or 2E8 to 2Efh. When the infrared port is configured in CMOS the second serial port will be disabled.

IEEE 1394/FireWire devices can be daisy-chained together and managed by a FireWire controller using a single set of system resources – DMA, IRQ, and I/O addresses. You need to configure a network interface card (NIC) so that it can communicate with the system software. If you have the newer Industry Standard Architecture (ISA) and Peripheral Component Interconnect (PCI) cards, you can do this using PnP.

Note For older legacy network cards, you can configure a NIC by setting hardware jumpers to a pattern that was on the card before it was installed in the computer. Legacy multimedia or specialized devices were created to use more than one group of IRQs or I/O addresses set by jumpers or dip switches. Newer devices use PnP to configure DMA, IRQ, and I/O addresses during the boot process.

Summary Transferring data from one location to another is the most frequent operation on a PC. To transfer data you need to allocate system resources – interrupt request (IRQ) channels, I/O addresses, and Direct Memory Access (DMA) channels – to the system's hardware devices. There are two forms of I/O devices – the system board's onboard I/O and peripheral devices. By using I/O addresses, the system communicates with its onboard intelligent devices. PC-compatible computers handle addresses differently according to whether they are classed in software as memory or I/O addresses. In a PC-compatible system, standard I/O adapters use I/O port addresses. Devices with I/O port addresses are identified according to their usage – system or I/O. I/O addresses are port addresses that the CPU uses to locate hardware devices and computer devices use IRQs to signal the CPU that they require services. For example, a floppy drive controller (FDC) has an IRQ value of 6 and an address range between 370 and 3F7.

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IDE types, connection, and configuration 1. EIDE specifications and characteristics The Integrated Drive Electronics (IDE) interface – also called the Advanced Technology Attachment (ATA) interface – is a system-level interface in which most controller electronics reside on the drive unit. As a result, information travels in parallel between the computer and the drive unit. In a system that uses an IDE interface, the controller circuitry on the drive handles the conversion of parallel data into serial data, and vice versa. As a result, the interface is not dependent on host computer design. The host computer only sees the data pattern presented by the IDE controller. Manufacturers put low-level formatting information, which the controller uses to align the drive and size its sectors, on IDE drives. The IDE controller removes the raw data – the low-level formatting data and the data for communication – from the read/write (R/W) heads of the drive and converts it into signals that the computer's buses can use. The standard IDE – or ATA – interface uses one 40-pin cable to connect a hard drive to a system board. The standard IDE interface supports a maximum throughput of 8.3 megabytes per second (MBps). The standard IDE specifications were updated to allow more than two drives to exist on the interface. The updated IDE standard includes the ATA-2, Enhanced Integrated Drive Electronics (EIDE), or AT Attachment Packet Interface (ATAPI) specifications. These specifications provide a maximum throughput of 16.6 MBps through a 40pin IDE signal cable and allow up to four IDE devices to operate in one system.

Note The ATAPI standard, derived from the ATA-2 standard, provides improved IDE drivers for use with CD-ROM drives and new Direct Memory Access (DMA) data transfer methods. With the updated IDE specification – ATA-2, EIDE, or ATAPI – a host can supply two IDE interfaces – IDE1 and IDE2 – each capable of handling a master and slave device in a daisy-chained configuration. Four more EIDE or ATA specifications, which came about through continued ATA standard development, are 

Ultra ATA

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  

Ultra ATA/66 Ultra ATA/100 Ultra ATA/133

Ultra ATA The Ultra ATA specification – also known as ATA-4 – can send data between an IDE device and the system at 33.3 MBps. This specification defined a new direct memory access (DMA) mode, but can support only slower programmed input/output (PIO) modes. Ultra ATA/66 Ultra ATA/66 or ATA-5 uses a special 40-pin cable that improves signal integrity by providing additional ground lines. It is therefore classed as an 80-wire cable. This specification can transfer data at 66.6 MBps. Ultra ATA/100 Ultra ATA/100 – also referred to as ATA-6 – uses a special 40-pin cable with additional grounding, like the ATA-4/Ultra ATA/66 specification. However, this specification can transfer data at 100 MBps. Ultra ATA/133 The Ultra ATA/133 connection transfers data at up to 133 MBps and supports hard drives larger than 137 GB. Like the ATA-5/Ultra ATA/66 and ATA-6/Ultra ATA/100 specifications, it uses a special 40-pin cable with additional grounding.

2. EIDE drive connection and configuration Enhanced Integrated Drive Electronics (EIDE) drives connect to computers using 40-pin cables and a controller. The controller is the support circuitry that acts as the intermediary between the hard drive and the external data bus. In EIDE drives, most controller functionality is built into the drive. So when the BIOS communicates with an EIDE drive, it is really communicating with the drive's onboard circuitry rather than with the connection on the motherboard. The external EIDE controller – a 40-pin male connection on the motherboard – simply provides connections to the rest of the system. Most PCs provide two EIDE controllers, a primary and a secondary controller, which each support up to two ATA drives. This means that most PCs can support up to four ATA devices.

Note Much older machines may have the controllers on a card that snaps into the motherboard. Although the primary and secondary controllers are equal in power and capability, the older style AT BIOS – for the AT motherboard – only searches for one of them – usually the primary controller – when the system boots up. When you install ATA devices, you therefore need to distinguish the primary controller from the secondary controller. To do this, you should consult user

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documentation for the motherboard and check the motherboard for labels that identify the ports. You need to configure drives you add to each EIDE controller differently depending on whether you add  

one hard drive two hard drives

one hard drive If you attach only one hard drive to an EIDE controller, you set the drive's jumpers to master. If you fail to set the jumpers correctly, the system won't recognize the drive. A master drive is a device that controls one or more other devices. Some drives have a third setting that is used when a single drive connects to a controller. Master and single drives are often the same setting on the hard drive. Some hard drives, however, require separate settings. If there is only one drive – a master or single drive – you attach the controller directly to that drive. two hard drives If you attach two hard drives to a single EIDE connection, you need to set one drive as the master and the other drive as the slave. You do this by configuring the jumpers for the drives. A master drive controls a slave drive and its processes. You can attach the controller to the master and then to the slave, to the slave and then to the master, or directly from the controller to single – master – drive.

An EIDE cable has two connectors – one for each device – on it. One is located in the middle and the other at the far end. Examples of EIDE devices include hard drives, DVD drives, CD-ROM drives, and zip drives. When attaching a hard drive and another device, such as a zip drive, you should always make the hard drive the master, and the zip drive the slave. The general rule is to place the fastest drive on its own, attached to the primary controller. You should correspond cables to connectors as plugging in incorrectly will prevent the PC from recognizing the drive. As a result, hard drive cables – like floppy drives – have a colored stripe that corresponds to the number-one pin on the connectors. Most EIDE drives include a diagram that shows you how to set their jumpers to configure them either as master or slave drives. If the jumpers aren't set correctly, the complementary metal-oxide semiconductor (CMOS) won't recognize the drive. If there isn't a label provided, you can check the drive manufacturer's web site or contact the manufacturer directly for the appropriate drive jumper settings. Hard disk drives sometimes have other jumpers that could be of importance during an installation. At the manufacturing plant, a common set of jumpers – but a set that you can ignore – is used for diagnostic purposes. This set is also used for special settings in other devices that use hard drives.

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Summary The Integrated Drive Electronics (IDE) interface –also called the AT Attachment (ATA) interface – is a system-level interface in which most controller electronics reside on the drive unit. As a result, information travels in parallel between the computer and the drive unit. Updated IDE specifications allow more than two drives to use the same interface. Some of these specifications include ATA-2, Enhanced Integrated Drive Electronics (EIDE), AT Attachment Packet Interface (ATAPI), Ultra ATA, Ultra ATA/66, Ultra ATA/100, and Ultra ATA/133. The controller acts as the intermediary support circuitry for the hard drive and the external data bus. One EIDE controller can connect up to two drives. You can connect a single EIDE controller to a master drive and then to a slave drive, to a slave drive and then to the master drive, or to a single master drive. To set a drive as a master or as a slave, you need to configure the drive's jumpers correctly.

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Physical connections and cabling 1. PIO modes, DMA modes, and Serial ATA ATA devices transfer data to and from the hard drive and memory via standardized protocols known as programmed input/output (PIO) modes and the more modern Direct Memory Access (DMA) modes. DMA modes are more popular than PIO modes because PIO modes are older and slower. Although DMA is faster because it bypasses the CPU, some nonhard drive ATA devices still use PIO modes. PIO mode is a term that the Small Forum Factor (SFF) standard committee developed to explain data transfer speeds. Originally, ATA drives could transfer data from the hard drive to RAM at a maximum rate of 3.3 megabytes per second (MBps) – PIO mode 0. Drive manufacturers improved this speed to 5.2 MBps – PIO mode 1 – and then to 8.3 MBps – PIO mode 2.

Programmed input/output speeds PIO speeds PIO mode

Cycle time – nanoseconds (ns)

Transfer rate (MBps)

0

600

3.3

1

383

5.2

2

240

8.3

3

180

11.1

4

120

16.6

To set the PIO mode for a system, you first need to check which mode the HDD, the controller, and the BIOS support. You then set the PIO mode for the system to the lowest of the three supported modes. Using a PIO mode that is faster than the one recommended by the drive manufacturer won't damage the HDD, but it could damage stored data. Newer PCs can communicate with the HDD during the boot process to set correct PIO modes automatically. To determine if a PC can do this, you enter the CMOS Setup utility and check whether it provides an Auto option for setting the PIO. If you enable automatic configuration of the PIO mode and errors occur when you install new devices, you need to re-enter the CMOS Setup utility and set a lower PIO mode.

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Note The Auto option for setting the PIO is usually found in the Advanced or Integrated Peripherals screens. DMA modes are more popular than PIO modes because they bypass the CPU and send data directly into memory, letting the CPU run programs freely. DMA data transfers can be 16-bits – single word – or 32-bits – double word – wide. Many systems have Peripheral Component Interconnect (PCI) that enables them to run at one of the Ultra DMA mode – or advanced DMA mode – speeds. These are Ultra DMA 3 (ATA/33), Ultra DMA 4 (ATA/66), and Ultra DMA 5 (ATA/100), which is now the most popular. Originally, most systems did not have BIOS support for DMA and needed thirdparty software drivers for support. Now, all BIOS support DMA, especially Ultra DMA. The CMOS setup utilities allow you to turn this option on or off and is almost always left on and users can enjoy the high speeds provided by Ultra DMA.

DMA modes DMA modes for 16-bit transfers DMA mode

Cycle time – nanoseconds (ns)

Transfer rate – megabytes per second (MBps)

0

960

2.1

1

480

4.2

2

240

8.3

DMA modes for 32-bit transfers DMA mode

Cycle time (ns)

Transfer rate (MBps)

0

480

4.2

1

150

13.3

2

120

16.6

3 Ultra DMA

60

33.3

4 Ultra DMA

30

66

5 Ultra DMA

20

100

Drives larger than 137 gigabytes (GB) can use  

parallel ATA (PATA) cables serial ATA (SATA) cables

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PATA cables are 80-pin IDE cables that the ATA-6 and higher standards use. SATA evolved from the PATA physical storage interface. Serial ATA is scalable and will allow future enhancements to the computing platform. Serial IDE cables are narrower and have fewer pins than parallel IDE cables, but are not limited by the 40 cm length restriction that applies to parallel cable. This enables you to connect to a device located at the top of a larger tower case more easily. IDE controllers need to use the same type of connector and cabling method as the HDD. It is, however, possible to use an adapter that will convert an 80conductor IDE connection – PATA – on the HDD to a serial ATA connection. If you want to install an IDE drive that uses a newer standard than your motherboard supports, you should install an IDE controller card that will support the drive and disable the IDE controller on the motherboard.

2. RAID levels To increase fault tolerance, you can use a simple volume or spanned volume in a redundant array of independent disks (RAID) configuration. A simple volume is a single hard drive. On dynamic disks, a simple volume is the same as the basic drive. A spanned volume is a set of drives that a system treats as a single volume or as a single virtual drive. A system that uses a spanned volume fills one drive with data before moving on to the next drive. As well as increasing volume capacity, spanned volumes improve system performance by allowing reads from multiple drives. RAID is a data storage method in which a system writes data to multiple HDDs. This allows data recovery if one HDD fails and improves system performance. To use a RAID configuration, the HDD controller and the OS must support RAID. If your PC or server motherboard does not support RAID drives, you can install a RAID-compliant IDE controller card and disable the IDE controller on the motherboard. Levels of RAID include   

RAID 0 RAID 1 RAID 5

RAID 0 The RAID 0 level uses disk striping – the system writes data to two or more hard drives alternately, creating a single logical drive on two or more physical drives. This increases the performance of the system – because more than one drive handles the required workload – and its volume capacity. RAID 0 doesn't provide parity error checking information, so although it improves performance, it doesn't provide fault tolerance. RAID 1 The RAID 1 level uses disk mirroring or disk duplexing to provide fault tolerance. Disk mirroring involves writing the same data to each of two HDDs. Disk mirroring uses only one HDD controller while disk duplexing uses two controllers – one for each drive. RAID 5

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A RAID 5 uses disk striping in which a system writes data to three or more drives alternately. It also distributes parity error checking information across these drives, which provides fault tolerance. If one HDD fails, the other drives can re-create the data stored on the failed drive.

Windows 9x doesn't support the use of striped or spanned volumes or any of the RAID levels. Windows NT supports RAID 0, RAID 1, and RAID 5, but not the use of striped or spanned volumes. Both Windows 2000 and Windows XP support striped or spanned volumes, and RAID 0, RAID 1, and RAID 5. You need to use dynamic drives to create any type of RAID volume with Windows 2000 and Windows XP. However, you can use basic drives if you are upgrading to these OSs from Windows NT and already have a RAID system set up. Dynamic drives in RAID configurations provide better fault tolerance than basic drives. This is because a dynamic drive includes a 1 MB database that contains information about all volumes on all drives in a system. This database automatically replicates on all drives. If one database fails, the system restores it automatically using a copy of the database on another drive. Using hard drives that allow hot- swapping is good practice if you have file servers using RAID 5 that need to work continuously and that store important data. If a drive fails, you can then replace it immediately, without having to disrupt file services by rebooting.

Note Hot-swapping refers to the ability to remove and add new devices without switching off the computer.

Summary The programmed input/output (PIO) mode of a system indicates its data transfer speed. The PIO mode that a system supports is the lowest of the three modes that the hard disk drive (HDD), controller, and basic input/output system (BIOS) support. Direct memory access (DMA) modes are more popular and faster than PIO modes because they bypass the CPU to send data directly into memory, letting the CPU run programs freely. Drives larger than 137 gigabytes (GB) can use the 80-wire IDE cable or serial ATA (SATA) cables. Redundant array of independent disks (RAID) is a method of data storage that provides fault tolerance and improved performance by writing data to multiple HDDs. Different RAID levels are RAID 0, RAID 1, and RAID 5.

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SCSI types and termination 1. SCSI specifications The small computer system interface (SCSI) is a hardware interface standard that enables you to connect multiple peripheral devices to a single board called a SCSI host adapter. The SCSI host adapter plugs into the motherboard, usually using a Peripheral Component Interconnect (PCI) slot. The advantage of SCSI is that you can daisy-chain multiple peripheral devices to one host adapter, using a single slot in the bus. Each SCSI device has a second port to connect the next device in line. The original SCSI interface allows 8-bit parallel data transmission. SCSI devices can be  

internal external

internal Internal SCSI devices – such as hard disks or tape drives – don't have their own power supplies. So you need to connect these devices to one of the system's power connectors. A ribbon cable connects these devices to the host adapter. external External SCSI devices – such as CD-ROMs or scanners – have built-in or plug-in power supplies that you need to connect to a commercial AC outlet.

You can implement the SCSI standard using different types of cables and connectors. For example, you can use an A-cable format, in which external connections use a 50-pin shielded cable with Centronics-type connectors, and internal connections use a 50-pin flat ribbon cable. The 68-pin P-cable format – using D-shell connectors – allows 16-bit transmission. And the 68-pin Q-cable format allows 32-bit transmission. For 32bit transfers, you need to use the P and Q cables in parallel. The maximum recommended length of a standard SCSI chain is 6 meters. But to minimize induced noise, the maximum recommended length of individual SCSI segments is less than 1 meter. However, you need to consider the length of internal cabling when you deal with SCSI cable distances. Because the length of internal cabling is about 0.9 to 1.5 meters, you need to reduce the maximum total length of the chain to about 4.5 meters. Updated SCSI specifications include   

Wide SCSI-2 Fast SCSI-2 Wide Fast SCSI-2

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 

Ultra SCSI Ultra 320 SCSI

Wide SCSI-2 The American National Standards Institute (ANSI) developed the Wide SCSI-2 specification to double the number of data lines available in the standard interface. The specification adds balanced, dual-line drivers for faster data transfer speeds. The maximum synchronous data transfer speed for this standard is 5 MegaBytes per second. It also provides an 8/16-bit bus standard and increases the standard cable and connector specification to 68 pins. It can support up to 15 devices. Fast SCSI-2 The Fast SCSI-2 specification increases the synchronous data transfer speed for the interface from 5 MegaBytes per second to 10 MegaBytes per second. It provides an 8/16-bit bus standard, and supports up to 7 devices. Under this specification, the system and the I/O device perform non-data message, command, and status operations in 8-bit asynchronous mode. After they've agreed on a bigger – or faster – file format, they perform transfers using the agreed word size and transmission mode. Fast SCSI-2 connections use 50-pin connectors. The higher speed of the specification reduces the maximum length of a SCSI chain to approximately 3 meters. Wide Fast SCSI-2 The Wide Fast SCSI-2 specification combines the improvements of Wide SCSI-2 and Fast SCSI2. It provides a maximum synchronous data transfer speed of 20 MegaBytes per second, and doubles the bus size of the original SCSI to 16 bits. It supports a chain of up to 15 additional devices. Ultra SCSI The Ultra SCSI specification provides a special high-speed serial transfer mode and special communications media, such as fiber-optic cabling. This update includes the following specifications – Ultra2 SCSI, Wide Ultra SCSI, Wide Ultra2 SCSI, and Wide Ultra3 SCSI. The Ultra SCSI specification provides a maximum synchronous data transfer speed of 20 MegaBytes per second and a bus size of 8 bits. It supports a chain of up to 7 devices. Ultra 320 SCSI The newest SCSI specification is Ultra 320 SCSI. It provides a maximum bus speed of 320 MegaBytes per second, uses a 16-bit bus, and supports up to 15 external devices. The Ultra 320 SCSI connection uses an 80-pin Single Contact Attachment (SCA) connector.

You can implement redundant array of independent disks (RAID) with Integrated Drive Electronics (IDE) or SCSI hard drives, depending on which type of RAID controller you select. Small business servers can often save money by using an IDE RAID solution. Generally, high-end servers use a SCSI RAID solution. SCSI RAID levels include RAID 0, 1, and 5.

2. Characteristics of SE, HVD, and LVD SCSI

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There are three types of SCSI signaling:   

single-ended (SE) High Voltage Differential (HVD) Low Voltage Differential (LVD)

single-ended (SE) All SCSI-1 devices are SE devices. This means that they communicate through one wire only per bit of data. SE SCSI devices can't differentiate between valid data and noise that invades the data stream from electrical power cables or other data cables nearby. The longer a SCSI cable, the more susceptible to noise interference it is. This limits the total length of an SE SCSI chain to about 6 meters. High Voltage Differential (HVD) SCSI-2 provides HVD signaling. HVD SCSI devices use two wires per bit of data – one for data and one for the inverse signal of this data. The SCSI device can reject noise in the data stream by calculating the difference between the two signals. This enables you to use a SCSI chain of up to 25 meters. Low Voltage Differential (LVD) Ultra2 SCSI introduced LVD signaling. In LVD devices, the signaling uses lower voltages on a twowire pair. LVD SCSI needs less power and is less costly than HVD. And LVD signaling supports cable lengths up to 12 meters.

LVD devices are compatible with existing SE devices. So if you plug an LVD device into an SE chain, it acts as an SE device. You should never use HVD devices with SE/LVD devices, because doing so may damage the devices. Because the cabling and connectors of SE and HVD devices seem so similar, you need to take care not to connect SE and HVD devices on the same SCSI chain.

3. Termination of SCSI devices SCSI host adapters can support up to seven internal or external devices. To increase the number of devices a system can support, you can use multiple SCSI host adapters in a single system. If you want to connect multiple SCSI devices to a SCSI host, every device, except the last one, must have two SCSI connectors – one for SCSI-In and one for SCSI-Out. It doesn't matter which connector you use for which function. However, if a SCSI device has a single SCSI connector only, you need to connect it to the end of the chain. Each SCSI device in a chain requires a unique ID number. If two SCSI devices are set to the same ID number, the system will fail to detect either one or both

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devices. The ID number of a SCSI device determines its priority level – the highest numbered device receives the highest priority. Although there are eight possible SCSI ID numbers for every controller, only seven are available for use with internal or external devices. The default for most SCSI host adapter cards is SCSI-7. In older SCSI devices, SCSI ID numbers were configured using jumpers on the host adapter card. In a block of configuration jumpers, you can count an open jumper pair as a binary 0, whereas a shorted pair represents a binary 1. With a three-pair jumper block, you can represent eight numbers – 0 through 7. In Plug-and-Play (PnP) systems, the basic input/output system (BIOS) configures the addresses of SCSI devices during the boot-up process by using information from the SCSI host adapter. Before the development of PnP technology, SCSI hard drives weren't configured as part of the system's CMOS setup function. Older operating systems such as DOS, Windows 3.x, and Windows 95 didn't support SCSI devices. So you had to load SCSI drivers during the boot process before the system could communicate with the drive. Windows 9x and Windows 2000 support SCSI devices. Because SCSI drives use a system level interface, no low-level formatting is necessary. So the second step involved in the installation of a SCSI drive is to partition it. When you transmit a signal down a wire, some of the signal reflects back up the wire and creates an echo which may interfere with legitimate signals coming down the wire. To prevent this problem, SCSI chains use termination at the end of the wire to absorb the signal and prevent the echo. You terminate only the ends of a SCSI chain. This means that you need to terminate only the two devices at the ends of the cable. Some devices can detect that they are on the end of a SCSI chain and can selfterminate. In most cases, however, you enable termination by setting a jumper or switch, or by plugging a resistor module into the open port. Types of terminators include   

passive terminators active terminators forced perfect terminators (FPTs)

passive terminators SCSI-1 devices that function at low speed and over short distances use passive terminators. Passive terminators use simple resistors only and are not very reliable.

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You should use passive termination with narrow SCSI only. active terminators Currently, most SE SCSI cables use active termination, recommended with SCSI-2. Active terminators include voltage regulators, as well as the simple resistors used in passive termination. Wide SCSI and Fast SCSI both use active termination. Active termination works better over long distances than passive termination. forced perfect terminators (FPTs) FPTs improve on active terminators by including a mechanism to force signal termination to the correct voltage. This eliminates most signal echoes and interference. FPTs are the most expensive and reliable terminators.

SE SCSI cables use passive terminators, active terminators, and FPTs. However, differential cables use either HVD or LVD terminators.

Summary Small Computer System Interface (SCSI) enables you to connect multiple devices to a single SCSI host adapter. Internal SCSI devices don't have their own power supply, whereas external SCSI devices have built-in or plug-in power supplies. Updated SCSI specifications include Wide SCSI-2, Fast SCSI-2, Wide Fast SCSI-2, Ultra SCSI, and Ultra 320 SCSI. Types of SCSI signaling include single-ended (SE), High Voltage Differential (HVD), and Low Voltage Differential (LVD) signaling. SE devices use one wire only per bit of data, whereas HVD devices use two wires per bit of data to minimize noise interference. LVD devices require less power than HVD and are compatible with SE devices. Each device requires a unique ID number, which determines its priority level. To prevent echo problems, you terminate the ends of a SCSI chain. Types of terminators include passive, active, and forced perfect terminators (FPTs).

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INSTALLING, CONFIGURING AND OPTIMIZING COMPUTERS

Installing printers, monitors, and UPSs 1. Installing a local printer A local printer connects to a computer via a port at the back of the system unit. You can connect more than one printer to a computer, but Windows automatically assigns one as the default printer. To install a local printer, you   

physically attach the printer install the printer drivers test the printer

Printers use two kinds of port technologies to communicate with computers:  

cable wireless

cable The standard port for a printer that communicates with a computer via cable is the LPT1 parallel port, but you can also connect a local printer to the computer's serial port or a PC card. Faster port standards include the small computer system interface (SCSI), universal serial bus (USB), and Institute of Electrical and Electronics Engineers (IEEE) ports – for example the IEEE 1284 and IEEE 1394 port. wireless Wireless printers communicate with computers via infrared signals or radio frequencies. To use a wireless printer, you need to install the drivers for the wireless port and enable the port.

Once you've attached the printer to the computer, you need to install the printer drivers. There are two ways to install the printer drivers for a local printer:  

the manufacturer's installation using the Add Printer Wizard

the manufacturer's installation Unless you have a number of printers of the same make, it's usually best to install printers using the printer driver provided by the manufacturer. To do this, you insert the printer driver CD to launch the manufacturer's installation program and follow the onscreen directions. using the Add Printer Wizard

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To avoid conflicts between similar printers, you use the Windows Add Printer Wizard. This utility allows you to install several printers that use the same drivers without overwriting the installed files.

To install a printer using the Add Printer Wizard in Windows XP, you   

access the Printers and Faxes window launch the Add Printer Wizard configure the printer

You begin by accessing the Printers and Faxes window. You select Start - Settings - Printers and Faxes. Alternatively, you press Ctrl+Esc and Shift+S+P. The Printers and Faxes window displays a list of all the available printers. In this case, no printers are currently installed. Next you launch the Add Printer Wizard. You select Add a printer. Alternatively, you press Alt+F+A. To complete the Add Printer Wizard in Windows XP, you     

choose to install a local printer manually select a printer port select the printer's make and model number name the printer print a test page

If you've used the manufacturer's installation program, you may need to test the printer manually. To do this in Windows XP, you   

access the Printers and Faxes window access the settings for the printer print a test page

Suppose that you have installed the HP2000 using the manufacturer's install disc and you want to test the printer. First you need to access the printer's settings. You select the HP2000 icon and select File - Properties from the menu bar. Alternatively, you select HP2000 and press Alt+F+R. Now you need to print a test page. You click the Print Test Page button. Alternatively, you press Alt+T. A message box asks you if the test page printed correctly. You click OK to return to the Properties dialog box for the printer.

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If the test page prints correctly, the printer drivers were installed successfully. If the test page fails to print or if the image is distorted, you can visit the manufacturer's web site to download a replacement driver. From the Printers and Faxes window in Windows XP, you can delete print jobs and change the default printer. You can also delete, troubleshoot, or share printers.

2. Installing video cards and monitors Versions of Windows after Windows 95 all support Plug and Play (PnP). Most monitors support PnP and are relatively easy to install. The monitor communicates with the system via a video cable that plugs into a video adapter card mounted on the motherboard. Older video cards connect to Industry Standard Architecture (ISA) or Peripheral Component Interconnect (PCI) slots on the motherboard, but newer cards use an Accelerated Graphics Port (AGP) video chip. The 16-bit ISA data bus runs at 8 or 8.33 MHz. It has a 62-pin connecter and a 36-pin auxiliary connecter. The PCI bus consists of a host bridge and a 32-bit, 124-pin connector or a 64bit, 184-pin connector. The 64-bit version runs at a maximum of 66 MHz and has a transfer rate of 132 MBps. For the monitor to function correctly, you need to install the video card on the appropriate slot on the motherboard. The 32-bit AGP bus is designed for data intensive graphics cards. It has 132 pins arranged in a single-slot, with a maximum transfer rate of 1,070 MBps. The video signal cable plugs into the 3-row, 15-pin female D-shell port mounted on a backing plate at the back of the computer. The monitor's power cable connects to the power socket on the back of the monitor and to a commercial power outlet. To install a PnP monitor, you need to complete the following steps:     

turn off the computer physically connect the monitor to the computer connect the monitor's power cord reconnect the computer to the power turn on the computer and the monitor

turn off the computer You turn off and unplug the computer before making the physical connections. physically connect the monitor to the computer To physically connect the monitor to the computer, you connect the signal cable to the video port. connect the monitor's power cord You connect the monitor's power cable to the monitor and a commercial power outlet. reconnect the computer to the power

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You reconnect the computer's power cable to the power port on the back of the computer and the power outlet on the wall. turn on the computer and the monitor Finally, you turn on the monitor and computer. If the monitor displays an image, the installation is complete.

The default resolution for a PCI-compatible VGA adapter is 640 by 480, with 16bit color and a 60 Hz refresh rate. However, you can change the display settings. To do this, you double-click the Display icon in the Control Panel window. When the Display Properties dialog box opens, you select the Settings tab. The Settings tabbed page in Windows 2000 allows you to change the color, resolution, and refresh settings:   

Colors drop-down list Screen area slider Advanced button

Colors drop-down list The Colors drop-down list allows you to change the number of colors that are available by selecting a different bit depth. The minimum number of colors is 256, but most cards allow 16-bit color. A 24-bit video card has approximately 16.7 million colors, but because bit depth increases exponentially, a 36-bit video card allows more than 68.7 trillion colors. Screen area slider You can optimize the screen resolution by adjusting the Screen area slider. Increasing the default setting will make the onscreen elements appear smaller. Higher screen resolutions include 800 by 600, 848 by 480, and 1024 by 768 pixels. Advanced button You click the Advanced button to open the video card's Properties dialog box. The keyboard alternative for this is Alt+D. On the Adapter tabbed page of this dialog box, you can select a different refresh rate from the Refresh Frequency drop-down list. The refresh rate should usually be as high as possible. Advanced video cards include a setting that automatically optimizes the refresh rate for the resolution and monitor chosen.

3. Uninterruptible power supplies An uninterruptible power supply (UPS) protects computers and peripheral devices – like monitors, modems, and tape drives – from data loss or data corruption caused by power failures or fluctuations in the AC current. During blackouts, brownouts, or spikes, the UPS battery provides a backup power source for all the computer equipment connected to it. This is known as transferring loads. An intelligent UPS allows you to control it using software. You can use the software to analyze the UPS, check for a weak battery, schedule maintenance tests, monitor the quality of electricity and the percentage of load during a blackout.

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You can also notify workstations about impending shutdowns, send pager notifications to managers in case of power failures, and automatically shut down servers. When buying a UPS you need to consider the rating – how much power the UPS will be required to provide, the runtime – the length of time the UPS will be required to provide power for and the price – how much you can afford to pay. The UPS power rating should be at least 125 percent of the wattage required by the load or all the equipment that it needs to support In addition to the power rating, runtime and price you should consider the amount of protection that the UPS provides. To do this, you check how much line conditioning the UPS provides and read the service policies, the warranty for the UPS, and the manufacturer's guarantee for the equipment connected to the UPS. Before installing the UPS, you should read all the safety instructions to ensure that you follow the correct installation procedures. A typical installation includes the following steps:    

check the intended load connect the UPS's power cord connect the PC's power cord to the UPS power up the system

check the intended load Before you install a UPS, you need to ensure that it can support the intended load. connect the UPS's power cord Once you've ensured that the UPS can support the load, you plug the UPS's power cord into the electrical outlet. connect the PC's power cord to the UPS Once you've connected the UPS to the power outlet, you disconnect the PC's power cord from the wall socket and plug it into the UPS's power outlet. power up the system Finally, you turn on the UPS and then turn on the PC.

Summary Local printers can be connected to a computer using cable, infrared signals, or radio waves. To install a local printer, you attach the printer to the LPT port or a faster port. Then you install the printer's drivers using the Add Printer Wizard or the manufacturer's driver CD, and print a test page. A monitor's adapter card plugs into an Industry Standard Architecture (ISA), Peripheral Component Interconnect (PCI), or Accelerated Graphics Port (AGP) slot on the motherboard. The monitor's signal cable uses the 3-row, 15-pin port on the adapter card. The default resolution for a PCI adapter is 640 by 480, 16bit color, and a 60 Hz refresh rate, but you can optimize these settings using the Display icon in Windows 2000.

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An uninterruptible power supply (UPS) protects electronic equipment from data loss or data corruption caused by power failures or fluctuations by transferring loads. An intelligent UPS has software that lets you perform various tasks. When buying a UPS, the power rating should be at least 125 percent of the wattage required by its intended load, and you should consider the amount of protection that the UPS provides.

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Analog dial-up, DSL, and cable modems 1. Installing analog dial-up modems Analog dial-up modems can be internal or external. Internal modems are adapter cards that fit into slots on the motherboard, while external modems plug into the standard modem or universal serial bus (USB) port. Although internal and external modems are installed differently, the general steps are similar. When installing an internal modem, you need to know if it is a Peripheral Component Interconnect (PCI) or an Industry Standard Architecture (ISA) card. PCI modems have a 124 pin edge connector. ISA modems have an edge connector featuring either a single 62-pin connector for an 8-bit card or a pair of connectors with 62 pins and 36 pins for a 16-bit card. You should also check the PC to find out which slots are free before purchasing the modem. Most older modems are legacy devices, so you have to configure them manually. To install an internal legacy modem, you need to     

prepare the system for installation configure the modem's IRQ and COM settings install the modem card in the system finish the hardware installation disable any competing COM ports

prepare the system for installation To prepare the system for installation, you turn off the computer, remove the cover from the system unit, and check if an appropriate expansion slot is available. Then you remove the relevant expansion slot cover from the back of the system unit. configure the modem's IRQ and COM settings Before configuring the modem's IRQ and COM settings, you need to check the user's manual to find out which jumper settings to use. Usually, the jumpers should be set to Plug and Play (PnP) by placing the jumper cover over the appropriate pins. install the modem card in the system To install the modem card, you plug the card into the appropriate expansion slot on the motherboard, secure the card, and screw in the slot cover on the back of the computer. You connect one end of the phone line to the modem's port, and the other end to the commercial phone jack. finish the hardware installation To finish the hardware installation, you replace the cover of the system unit. disable any competing COM ports To prevent hardware conflicts, you need to disable any competing COM ports in the complementary metal-oxide semiconductor (CMOS) Configuration utility. For example, you may need to disable COM2 on the motherboard.

Before installing an external legacy modem, you need to check the back of the machine to find out if a COM port is available. If not, you may need to buy a

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serial modem card. The standard COM ports are a 9-pin male and a 25-pin male D-shell connector. To install an external modem, you   

connect the modem to the system connect the modem to the power supply access CMOS to enable the appropriate COM port

You plug one end of the modem's data cable into the modem's 25-pin RS-232 port, and the other end into the computer's 25-pin serial port. Then you connect the phone line to the phone jack – known as the Line socket – on the computer and on the modem. You can also connect a telephone handset to the modem using the Phone socket. Before plugging the modem into the power outlet, you should ensure that the modem is switched off. To access the CMOS setup utility, you need to reboot your computer and press Delete before Windows launches. On the ports page of the CMOS Setup utility, you need to enable the appropriate serial port – for example COM2 Most newer modems are PnP, so Windows will automatically detect and install a new modem the next time the computer starts up. The steps for installing an internal or external modem using this method are the same. To install a PnP modem, first you physically connect the modem and turn on the computer. When you start the computer, the Detect New Hardware Wizard launches automatically and you follow the onscreen instructions.

Note Some modems may require you to reboot the PC a second time to complete installation. Once you have physically connected the modem to the PC, you need to configure it. You begin by accessing the Control Panel window. You select Start - Settings - Control Panel. Alternatively, you press Ctrl+Esc and Shift+S+C. The Control Panel allows you to configure the computer's software and hardware components. You need to access the modem settings, so you double-click Modems. In the Modems Properties window, you select the modem that you want to configure – in this case Sportster Flash V.90 Voice PnP.

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You click the Properties button. Alternatively, you press Alt+R. On the General page of the Properties dialog box for the modem, you can change the speed settings for the modem. You should always check that the maximum speed is as fast as possible. In this case, the maximum speed is 115200. To check the port protocol settings, you click the Connection tab. In this case, the port protocol is set to 8 bits, no parity, and 1 stop bit, which is the recommended configuration. Next, you need to check that hardware flow control is enabled. On the Connection tabbed page, you click Advanced. Alternatively, you press Alt+V. To enable hardware flow control, you ensure that the Use flow control checkbox is selected on the Advanced Connections Settings dialog box. You can set up the modem to make calls without using other software. To do this in Windows 98, you need to   

access My Computer access the dial-up networking settings create and configure a new connection

You double-click the My Computer icon on the desktop to access the contents of the local computer. To access the dial-up networking settings, you double-click the Dial-up Networking icon in the My Computer window. From the Dial-Up Networking window, you can launch the Make New Connection utility to create a new connection. You double-click the Make New Connection icon. To complete the wizard, you need to  

name the connection provide a phone number

You can now configure a modem in Windows 98. To configure a modem in Windows XP, you  

access the phone and modem settings configure the modem properties

You can use the HyperTerminal application to test the modem. To do this in Windows XP, you   

launch the HyperTerminal utility provide a description and phone number select a modem

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

make the call

To launch the HyperTerminal application, you select Start - Programs Accessories - Communications - HyperTerminal. In the Connection Description dialog box, you type a name for the connection – for example Analog dial-up modem connection – in the Name text box and click OK. In the Connect To dialog box, you type the phone number in the Phone number text box and click OK. In the Connect dialog box, you click Dial to make the call.

1. Installing analog dial-up modems Analog dial-up modems can be internal or external. Internal modems are adapter cards that fit into slots on the motherboard, while external modems plug into the standard modem or universal serial bus (USB) port. Although internal and external modems are installed differently, the general steps are similar. When installing an internal modem, you need to know if it is a Peripheral Component Interconnect (PCI) or an Industry Standard Architecture (ISA) card. PCI modems have a 124 pin edge connector. ISA modems have an edge connector featuring either a single 62-pin connector for an 8-bit card or a pair of connectors with 62 pins and 36 pins for a 16-bit card. You should also check the PC to find out which slots are free before purchasing the modem. Most older modems are legacy devices, so you have to configure them manually. To install an internal legacy modem, you need to     

prepare the system for installation configure the modem's IRQ and COM settings install the modem card in the system finish the hardware installation disable any competing COM ports

prepare the system for installation To prepare the system for installation, you turn off the computer, remove the cover from the system unit, and check if an appropriate expansion slot is available. Then you remove the relevant expansion slot cover from the back of the system unit. configure the modem's IRQ and COM settings Before configuring the modem's IRQ and COM settings, you need to check the user's manual to find out which jumper settings to use. Usually, the jumpers should be set to Plug and Play (PnP) by placing the jumper cover over the appropriate pins. install the modem card in the system To install the modem card, you plug the card into the appropriate expansion slot on the motherboard, secure the card, and screw in the slot cover on the back of the computer. You connect one end of the phone line to the modem's port, and the other end to the commercial phone jack.

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finish the hardware installation To finish the hardware installation, you replace the cover of the system unit. disable any competing COM ports To prevent hardware conflicts, you need to disable any competing COM ports in the complementary metal-oxide semiconductor (CMOS) Configuration utility. For example, you may need to disable COM2 on the motherboard.

Before installing an external legacy modem, you need to check the back of the machine to find out if a COM port is available. If not, you may need to buy a serial modem card. The standard COM ports are a 9-pin male and a 25-pin male D-shell connector. To install an external modem, you   

connect the modem to the system connect the modem to the power supply access CMOS to enable the appropriate COM port

You plug one end of the modem's data cable into the modem's 25-pin RS-232 port, and the other end into the computer's 25-pin serial port. Then you connect the phone line to the phone jack – known as the Line socket – on the computer and on the modem. You can also connect a telephone handset to the modem using the Phone socket. Before plugging the modem into the power outlet, you should ensure that the modem is switched off. To access the CMOS setup utility, you need to reboot your computer and press Delete before Windows launches. On the ports page of the CMOS Setup utility, you need to enable the appropriate serial port – for example COM2 Most newer modems are PnP, so Windows will automatically detect and install a new modem the next time the computer starts up. The steps for installing an internal or external modem using this method are the same. To install a PnP modem, first you physically connect the modem and turn on the computer. When you start the computer, the Detect New Hardware Wizard launches automatically and you follow the onscreen instructions.

Note Some modems may require you to reboot the PC a second time to complete installation. Once you have physically connected the modem to the PC, you need to configure it. You begin by accessing the Control Panel window. You select Start - Settings - Control Panel. Alternatively, you press Ctrl+Esc and Shift+S+C.

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The Control Panel allows you to configure the computer's software and hardware components. You need to access the modem settings, so you double-click Modems. In the Modems Properties window, you select the modem that you want to configure – in this case Sportster Flash V.90 Voice PnP. You click the Properties button. Alternatively, you press Alt+R. On the General page of the Properties dialog box for the modem, you can change the speed settings for the modem. You should always check that the maximum speed is as fast as possible. In this case, the maximum speed is 115200. To check the port protocol settings, you click the Connection tab. In this case, the port protocol is set to 8 bits, no parity, and 1 stop bit, which is the recommended configuration. Next, you need to check that hardware flow control is enabled. On the Connection tabbed page, you click Advanced. Alternatively, you press Alt+V. To enable hardware flow control, you ensure that the Use flow control checkbox is selected on the Advanced Connections Settings dialog box. You can set up the modem to make calls without using other software. To do this in Windows 98, you need to   

access My Computer access the dial-up networking settings create and configure a new connection

You double-click the My Computer icon on the desktop to access the contents of the local computer. To access the dial-up networking settings, you double-click the Dial-up Networking icon in the My Computer window. From the Dial-Up Networking window, you can launch the Make New Connection utility to create a new connection. You double-click the Make New Connection icon. To complete the wizard, you need to  

name the connection provide a phone number

You can now configure a modem in Windows 98. To configure a modem in Windows XP, you  

access the phone and modem settings configure the modem properties

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You can use the HyperTerminal application to test the modem. To do this in Windows XP, you    

launch the HyperTerminal utility provide a description and phone number select a modem make the call

To launch the HyperTerminal application, you select Start - Programs Accessories - Communications - HyperTerminal. In the Connection Description dialog box, you type a name for the connection – for example Analog dial-up modem connection – in the Name text box and click OK. In the Connect To dialog box, you type the phone number in the Phone number text box and click OK. In the Connect dialog box, you click Dial to make the call.

2. DSL and cable modems Broadband technologies – like digital subscriber lines (DSL) and cable – can transmit several types of data at the same time, including audio, video, and text. Most broadband connections use network interface cards (NICs) and cable connections. If you use a cable modem to connect to the Internet, the network cable connects to the network port on the NIC and the port on the cable modem. The cable modem connects to the cable television outlet via a TV cable. It also has a power cable that connects to the electrical power outlet. Broadband connections use the Point-to-Point over Ethernet (PPPoE) protocol, which is included in Windows XP. For a DSL connection, the phone line plugs into the DSL box. Telephone companies provide DSL and Integrated Services Digital Network (ISDN) lines. Users can use these lines via a DSL/ISDN converter connected to the computer by a NIC and a network cable. The DSL/ISDN converter can include a router, so that users can share the same telephone line. Once you have installed and connected the cable modem, you connect to the relevant Internet service provider (ISP). The first time you connect to the ISP, it assigns your computer an IP address, subnet mask, and default gateway address, and provides the IP address for the domain name server. To install a broadband connection, you    

install the NIC and its drivers connect the computer to the cable modem or DSL box install and configure TCP/IP install the physical connections

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

install the software for the connection

Suppose that you want to install a cable modem. You begin by installing the NIC on the motherboard and loading its drivers. Then you install TCP/IP and bind it to the NIC. This means that you configure the protocol to use the NIC. Once you've installed and configured TCP/IP, you shut down the computer and install the physical connections. To do this, you connect the computer and the cable modem using a network cable. You plug in and turn on the modem and connect it to the cable television's outlet via the TV cable. To finish the installation, you restart the computer to check the Internet connection. You should automatically connect to the Internet. In Windows 98, you can use the Winipcfg utility to troubleshoot the connection. To do this, you   

launch the Winipcfg utility release all the addresses renew the addresses

To begin troubleshooting the connection, you click Start - Run. You type winipcfg in the Open text box of the Run dialog box and click OK. In the IP Configuration window, you select the cable modem from the drop-down list and you click Release All. Then you click Renew. To check an Internet connection in Windows 2000, you use the ipconfig command. To do this, you  

access the MS-DOS prompt use the /release switch



use the /renew switch

To troubleshoot a malfunctioning cable connection, you can turn off the computer and modem, wait five minutes, and then restore power. If the problem persists, you should ask the manufacturer's help desk to release and restore the connection.

Summary To install an internal legacy modem, you turn off the computer, configure the jumper settings, install the modem card, and disable competing COM ports. To install an external legacy modem, you connect the data cable, the phone line, and the power cable. Windows automatically detects and installs Plug and Play modems. You should check that the modem uses the highest speed possible, that hardware flow control is enabled, and test the modem. You can also set up the modem to make calls without using other software.

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Broadband modems, like digital subscriber lines (DSL) and cable modems, can transmit different types of data simultaneously. To install a broadband connection, you install the network interface card (NIC) on the motherboard and install its drivers. You connect the computer to the cable modem or DSL box, install and configure TCP/IP, install the physical connections, and install the software for the connection. You can release and renew the IP address assigned to the connection using the Winipcfg or Ipconfig utilities.

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Digital, infrared, and wireless devices and PDAs 1. Retrieving data from a digital camera Like scanners, digital cameras record images in a digital format by translating light signals into digital values. This allows you to store, transmit, manipulate, and print photo-quality images using software, including the image-editing applications bundled with your camera. Digital cameras transfer images to computer using TWAIN technology, an interface standard originally designed for scanners. Most digital cameras are bundled with TWAIN-compatible driver software. You can transfer data from a digital camera to a computer using   

cable technology wireless technology external storage devices

cable technology Newer digital cameras use universal serial bus (USB) or FireWire cables to upload images from a digital camera, but you can connect the cable to a serial port or a parallel port. The cable attaches to the camera or to its cradle. wireless technology You can use wireless technologies – for example an infrared connection – to transfer images to a computer. external storage devices Flash RAM cards are portable devices used to store various kinds of data, including photos from digital cameras. You connect the flash card to the computer using a USB cable. Depending on your printer, you can also print images directly from the flash card.

Many people use the Joint Photographic Experts Group (JPEG) standard to store and transfer photos, because it has a built-in compression function for large images. Having transferred the images to the PC, you can use image editing software to re-touch or add effects to the image. You can print out the final image, show it on-screen, or send it by e-mail.

2. Installing infrared transceivers Infrared devices, like wireless keyboards, mouse devices, and printers, communicate with a computer via a transceiver that plugs into a serial port on the PC. Computers can also use infrared transceivers to connect to a network. This means that the serial port will not be available for other devices.

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The transceiver relays the information from the network or infrared device to the computer via the serial port's resources. In order to communicate with the computer, the transceiver creates virtual serial and parallel ports for the infrared devices that are installed. A transceiver connected to COM1 may use COM3 as the default virtual serial port, and LPT2 as the virtual parallel port. The infrared system uses the COM1 port's Interrupt Request (IRQ) settings and I/O address. Some motherboards include a built-in 5-pin connector for infrared transceivers. However, this connector is usually only compatible with certain transceivers. Motherboards with built-in infrared connectors use the universal asynchronous receiver-transmitter (UART) to control the serial ports. You need to enable UART in the complementary metal-oxide semiconductor (CMOS) setup utility. The main disadvantage of infrared devices is the line-of-sight issue. This means that the infrared device must be in a direct line with the transceiver. As soon as the line of sight is obstructed, the connection will terminate and the device will stop functioning until the connection is restored. Newer infrared devices are Plug and Play (PnP). Windows automatically installs PnP devices when the computer boots up. Non-PnP devices are known as legacy devices. To install a transceiver, you   

connect the transceiver set the virtual ports start the transceiver

You begin by connecting the device and turning on the computer. Depending on your configuration, you may need to complete the Add New Hardware Wizard to configure the virtual ports for the infrared device – for example if you're using a legacy transceiver. You double-click the Add New Hardware icon in Control Panel. Instead of running the Add New Hardware Wizard, you can also run the driver setup program provided by the manufacturer. To start the PnP or legacy transceiver, you double-click the Infrared icon in the Control Panel window.

3. PDAs and wireless LAN standards Personal digital assistants (PDAs) are hand-held computers that combine phone, fax, desktop computer, and networking functions, for example word processing, e-mail, and web browsing. You can connect a PDA to a PC or a notebook using a universal PDA cradle. To do this, you connect the cradle's cable to the computer's serial or USB port. The PDA coordinates the transfer of information between the PDA and the computer in a process known as synchronization. For a faster connection speed than cable, you can connect a PDA to a computer via wireless technology.

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To do this, you need to ensure that both devices have wireless transceivers installed and use the same wireless standard, for example Bluetooth.

Note You may need to install an add-on transceiver on the PDA. To set up a connection between the PDA and a PC, you    

read the PDA's manual to find out if you need to install additional synchronization software install the synchronization software on the PC connect the PDA to the PC synchronize the data

Once the software is installed and the PDA is connected to the PC it should now be possible to synchronize the data. If synchronization fails, you should check the physical connections. If you're using a USB port, you should also check the Device Manager to ensure that there are no hardware conflicts with other ports. You should also ensure that the ports are enabled in CMOS and that the PDA is powered up. You can also reinstall the PDA driver. If this doesn't work, consult the PDA manual or the manufacturer's website. A PDA or laptop can connect to a wireless local area network (WLAN) via a wireless access point (AP). A WLAN connects computers and devices via radio or infrared signals using wireless network interface cards (NICs). Wireless standards include  

Bluetooth Institute of Electrical and Electronics Engineers (IEEE) 802.11

Bluetooth Bluetooth wireless connections have a range of 10 metres, use the 2.4 GHz radio band, and are easy to configure. For example, a PDA can use a Bluetooth connection to connect to a cellphone and dial into a remote network. Institute of Electrical and Electronics Engineers (IEEE) 802.11 The most common WLAN standard is IEEE 802.11b, also known as Wi-Fi or Airport. It uses the 2.4GHz radio band and has a range of 100 metres. 802.11a uses the 5.0 GHz band and has a range of 50 meters, but it's more resistant to interference. Like 802.11a, 802.11g is much faster than Wi-Fi, but it uses the same frequency range.

The main disadvantages of a WLAN are 

speed

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

security

speed WLANs are usually slower than cable networks, and tend to get slower if a lot of users are logged on. security An unauthorized user can intercept wireless transmissions, so WLANs need additional security measures. For example, you can specify which NICs are allowed access to the AP, and use encryption software to protect sensitive data.

Summary Digital cameras record images in a digital format so that you can transmit, store, manipulate, and print photo-quality images using TWAIN technology. You can transfer data from a digital camera to a computer using infrared or cable technology, for example serial, parallel, universal serial bus (USB), or FireWire. You can also store and transfer images using a flash RAM card. Infrared devices use transceivers to connect to a computer or a network. However, the infrared device must be in a direct line of sight with the transceiver. The transceiver plugs into the computer's serial port or a built-in, infrared, 5-pin connector. To install a transceiver, you connect the device, and turn on the computer. You may need to complete the Add New Hardware Wizard to configure the virtual ports of the infrared device. You connect a personal digital assistant (PDA) to a PC or a notebook using a universal PDA cradle connected to the computer's serial or USB port. To connect a PDA to a computer using wireless technology, you need to ensure that both devices use the same wireless standard, for example Bluetooth, Institute of Electrical and Electronics Engineers (IEEE) 802.11, IEEE 802.11a, 802.11g, or Wi-Fi. Wireless PDAs use wireless access points (APs) to connect to wireless local area networks (WLANs).

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Upgrading the system board Introduction As new computer components that offer improved performance become available, it's important to upgrade a computer system so that it doesn't become obsolete. You can choose to upgrade a system by replacing the entire motherboard or to upgrade certain components only.

Upgrading a motherboard Upgrading to a new motherboard generally provides greater performance benefits than upgrading individual components only. This is because a new motherboard provides faster microprocessors and memory units, newer chipsets, and faster frontside buses and I/O connections. However, this is generally more expensive than upgrading individual components. It may also mean that you'll need to purchase new adapters, software, and peripheral devices that are compatible with the new board.

Upgrading components Components on the motherboard that you can upgrade include the    

microprocessor ROM basic input/output system (BIOS) integrated circuit (IC) RAM modules and cache memory complementary metal-oxide semiconductor (CMOS) backup battery

The microprocessor, ROM BIOS, and RAM modules are components known as field replaceable units (FRU) that you can replace individually to improve a system's performance.

Microprocessor upgrades Almost every type of microprocessor has an upgrade version or a clone microprocessor that is pin-for-pin compatible with older designs. This makes it easy to upgrade an existing microprocessor. To replace an existing microprocessor with an upgrade, you should   

ensure that the upgrade is compatible with the current hardware – pin configuration, socket, or slot – on the motherboard ensure that you are able to upgrade the existing BIOS to support the specifications of the new microprocessor remove the existing microprocessor and insert the new microprocessor in the socket or slot so that pin 1 on the microprocessor matches pin 1 of the socket

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

configure the motherboard – automatically or manually – for the upgrade

Most new systems include an auto-detect function that detects a new microprocessor and determines the appropriate configuration settings for it. During the configuration phase of the boot procedure, the new microprocessor exchanges information with the system's Plug and Play (PnP) BIOS to configure these settings. For older systems, you need manually to configure the core voltage, bus speed, and bus frequency ratio configuration jumpers to the settings specified in the installation manual for the microprocessor. If these settings are incorrect, it may    

burn the upgraded microprocessor prevent the computer system or the operating system from starting cause random errors during functioning cause the system to identify an incorrect processor type or speed during the power-on self test (POST) routine

Upgrade paths are available for certain microprocessors used in PCs. The upgrade path shows what microprocessor types are compatible with which socket configurations. So, for example, if you have a Slot 1 type socket on the motherboard, you can fit a Celeron, Pentium II, or Pentium III processor. So you can upgrade to a Pentium II or III processor.

Microprocessor upgrade paths Itanium/Intel – 733 megahertz (MHz) to 800 MHz)

418 Intel - pin grid array (INT-PGA)

Socket 418

Voltage regulator module (VRM) – 1.7 volts (V)

Pentium IV Xeon – 1.4 gigahertz (GHz) to 2.2 GHz

603 INT-PGA

Socket 603

VRM – 1.5 V to1.7 V

Pentium IV – 1.4 GHz to 2.2 GHz

478 flip chip pin grid array (FC-PGA)

Socket 478

VRM – 1.5 V to1.7 V

Pentium IV – 1.3 GHz to 2.0 GHz

423 FC-PGA

Socket 423

VRM – 1.7 V

Advanced Micro Devices (AMD) Athlon

242 Slot A

Slot A

VRM – 1,2 V to 2.2 V

AMD Athlon, Duron

462 staggered pin grid array (SPGA)

Socket A VRM –1.2 V to 2.2 V

Cyrix III, Celeron, Pentium III

370 SPGA

Socket 370

VRM – 1.1 V to 2.5 V

AMD K6-2, K6-2+, K6-III, K6-III+, Pentium MMX, Pentium Pro

321 SPGA

Super socket 7

VRM – 2.0 V to 3.5 V

Celeron, Pentium II, Pentium III

242 single edge contact cartridge (SECC)/ single edge processor package

Slot 1

VRM – 1.5 V to 2.5 V

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Microprocessor upgrade paths Itanium/Intel – 733 megahertz (MHz) to 800 MHz)

418 Intel - pin grid array (INT-PGA)

Socket 418

Voltage regulator module (VRM) – 1.7 volts (V)

Slot 2

VRM – 1.5 V to 2.5 V

Pentium – 75 MHz to 200 321 SPGA MHz

Socket 7

VRM – 2.5 v to 3.6 V

Pentium Pro

Socket 8

VRM – 2.2 V to 3.5 V

(SEPP) Xeon

330 SECC-2

387 SPGA

BIOS upgrades If you upgrade the microprocessor, you should also upgrade the BIOS so that it can support the new microprocessor. For newer motherboards, you do this by flashing – electrically altering – information stored in the BIOS with the latest compatibility firmware. To do this, you run an executable file – from the hard disk drive (HDD) or floppy disk drive (FDD), or downloaded from the manufacturer's web site. This file transfers the new BIOS information into the BIOS integrated circuit (IC), where it is stored until it is rewritten –even when no power is supplied to the IC. If the system BIOS doesn't have a flash option and doesn't support a new microprocessor, you should update the BIOS IC so that it is compatible with the new processor and the motherboard's chip set. You can obtain an upgraded BIOS IC from the motherboard manufacturer. It's a good idea to make a floppy disk backup copy of the BIOS settings before you flash the BIOS so that you can recover the existing settings if necessary. You should also record the complementary metal-oxide semiconductor (CMOS) configuration information before flashing so that you can reinstall these settings on the updated BIOS.

Memory upgrades Upgrading RAM significantly increases the operating speed of a computer system. It does this by enabling the system to access more data from memory, rather than from the HDD. To upgrade memory, you need to install new memory modules in empty single inline memory modules (SIMM) or dual inline memory modules (DIMM) slots. RAM and other memory devices are rated in access time rather than clock speed. For example, a 50-nanosecond (ns) RAM device is faster than a 60-ns device. Before you upgrade the memory in newer PCs, you should check 

the memory types that can be installed on the motherboard

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  



the number and type of ICs of the new memory modules, to ensure that they are compatible with existing modules and with each other the speed of the new modules, to ensure their compatibility with the motherboard the arrangements of memory modules – whether memory modules must be configured in banks of the same type – that you can use with the existing memory board, as specified in the user manual any memory configuration settings that you need to make to accept the new memory capacity, if a system doesn't configure these automatically

On older systems – pre Pentium and pre DIMM modules – you had to install 30 or 72-pin SIMMs in banks of the same type, with either two or four modules to a bank. Although different memory modules are physically compatible, you should avoid mixing memory types when upgrading RAM. Incorrectly matching memory speeds and memory styles – for example, registered/unregistered and buffered/unbuffered – can prevent a system from booting and cause soft memory errors. Cache memory is a special type of RAM accessed by the CPU. It can be accessed much faster than ordinary RAM – but the cache is a lot smaller. For very old CPUs and the classic Pentium, the cache memory was outside the CPU, with an integrated circuit (IC) of its own. With the Pentium II, the cache was moved into the CPU housing. If the motherboard has cache memory installed in sockets, you can increase system performance by adding memory to the cache. This usually requires the additional installation of cache ICs in vacant sockets. If the sockets are already full, you can remove existing cache chips and replace them with faster, highercapacity ones.

CMOS backup battery The CMOS backup battery maintains basic configuration settings while your PC is off. Frequent CMOS errors are a sign of a dead battery. You should replace the CMOS battery every two years, especially if you usually upgrade instead of replacing your PC. To replace the backup battery, you boot your PC and enter Setup mode to record the settings in the BIOS menus so that you can re-enter these once you've replaced the battery. However, if the battery has failed completely and you're receiving a CMOS checksum error message, you'll need to enter new settings once you've installed the replacement battery. You switch off your PC, open the computer case, and locate the battery on the motherboard. You can consult the user manual for the specifications and exact location of the battery. You then remove the old battery and replace it with the new one, replace the case, switch on your computer, and enter the appropriate settings in Setup mode. It's a good idea to record the date on which you replace the battery so that you know when it's due for another replacement.

Power supply upgrades

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If a system experiences intermittent errors or unexpected reboots, it may be because the power supply unit needs to supply a higher wattage to the system. In this case, you need to upgrade the power supply unit. You need to check which type of power supply unit your system uses before purchasing a replacement. Common types are the newer ATX power supply, which uses a dual-row motherboard power connector, and the older AT power supply, which uses two single-row power connectors. When purchasing the upgrade, be sure to choose one that matches or slightly exceeds the power needs of your PC. Most systems can operate effectively with a 250-watt or 300-watt supply. However, the general guideline for determining your computer's power supply needs is to add up the power requirements of each component and then add another 30 percent.

Component power requirements Component

Power requirement (watts)

Motherboard

15 to 30 W

700-megahertz (MHz) Celeron chip

21

1-gigahertz (GHz) Pentium III chip

33

1.2-GHz Athlon chip

70

RAM

7 W per 123 megabytes (MB)

PCI add-in card

5

Network card

4

Graphics card

20 to 50 W

Floppy drive

5

CD-ROM, CD/RW, or DVD-ROM drive

10 to 25 W

IDE hard drive

5 to 15 W

Standard Small Computer System Interface (SCSI)

10 to 25 W

10K- or 15K-revolutions per minute (rpm) SCSI hard drive 10 to 45 W

To replace a power supply unit, you first disconnect your system from any power connectors. For ATX power supplies, you remove the connectors from the motherboard and drives. For AT power supplies, you remove the power switch and grounding wire. You then remove the old power supply by extracting the screws that hold it in place and carefully lifting the unit out of the case. You secure the new power supply with screws and reconnect all power connectors, reconnect the system to the commercial power supply, and switch on the system. If the computer seems dead, check all connections and then try again.

Summary To improve system performance, you can choose to upgrade a system by replacing the motherboard or by replacing individual components on the

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motherboard only. Components you can upgrade include the microprocessor, the basic input/output system (BIOS), RAM modules, and cache memory. Before you replace a microprocessor with an upgraded one, you should ensure that the upgrade is compatible with the current hardware and BIOS. You then remove the existing microprocessor from its socket and insert the new one. Newer systems that support Plug and Play (PnP) configure settings for the upgrade automatically, whereas older systems may require you to adjust settings manually. Once you upgrade a microprocessor, you should also upgrade the BIOS. For newer system boards, this entails flashing – electrically altering – information stored in the BIOS with the latest compatibility firmware. In case the new BIOS information does not work with your system, it is a good idea to make a floppy disk backup copy of the BIOS settings before you flash the BIOS. You should also record the CMOS configuration information before flashing so that you can reinstall these settings on the updated BIOS. Increasing or upgrading RAM significantly increases the operating speed of a computer system. To upgrade RAM, you install new memory modules in empty single inline memory module (SIMM) or dual inline memory module (DIMM) slots. It is important to avoid mixing memory types on a motherboard, and to check that memory configuration settings are appropriate for the new memory modules you install. If the power supply unit for a system provides too low a wattage, the system may experience intermittent errors or unexpected reboots. In this case, you need to upgrade the power supply unit with one that has a higher capacity.

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Upgrading adapter cards, hard drives, and laptops 1. Upgrading portable computers Portable computers – laptops and notebooks – use specialized peripheral devices.    

Portable drives PC cards Batteries Portable memory PC cards

Portable drives Originally, portable computers included a floppy disk drive (FDD) and a hard disk drive (HDD) as standard equipment. Newer portable computers often have a CD-ROM drive and an HDD as standard internal units. To address the portable computer market's need for compact devices, manufacturers developed smaller drives. These include, for example, a 2.5 inch form-factor HDD, a low-profile 3.5 inch FDD, and a combination FDD/CD-ROM drive. Many newer portable computers include swappable drive bays that allow you to change the combination of the unit's internal drives. In some cases, you can even remove a disk drive that's not needed and replace it with another component – for example, an extra battery. Before purchasing a new disk drive, you should check its physical size and layout to ensure that it will fit inside the laptop. You check its power consumption to assess whether the laptop can supply the necessary power and how it will impact on the battery life. You also need to check that the basic input/output system (BIOS) of the computer supports the new drive, to ensure that it's compatible with the laptop. To replace an internal disk drive, you need to disassemble the computer case. Some newer portable computers allow hot swapping of drives – their replacement while the computer is still on. For older systems, you generally need to turn off the computer, install a new drive, and then reboot. PC cards Portable computers use Personal Computer Memory Card International Association (PCMCIA) cards – or PC Cards – to allow you to attach peripheral devices. PC cards support hot swapping – so you can install or replace them while a portable computer is on. A PC card is 5.38 by 8.56 centimeters – about the size of a credit card. Each type of card, however, has a different thickness. PC cards use a 68-pin, slide-in pin and socket arrangement. They can be used with 8-bit or 16-bit data bus machines and operate on 3.3 volts (V) or 5 V power supplies. Types of PC cards include Type I, Type II and Type III. Type I PC cards were introduced in 1990. They are 3.3 mm thick and function as memory-expansion units. Type II cards were introduced in 1991 and are 5 mm thick. They support almost all original expansion functions – for example, modems or local area network (LAN) cards – except removable HDD units. Type II slots are backward compatible, so you can use Type I cards in them. Type III cards were most recently introduced and are 10.5 mm thick. They were developed for use with removable HDDs. Type III slots are backward compatible, so you can attach Type I and Type II cards to them.

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Most portable computers include two Type II slots. Type III cards use only one of the two slots but take up the entire opening. So you can use two Type I cards, two Type II cards, or one Type III card on these computers. The PCMCIA standard provides for up to 255 adapters – such as hard drives, small computer system interface (SCSI) adapters, and network adapters, which can each support up to 16 cards. As a result, it allows a PC to support more than 4000 PC cards. Batteries You can connect portable computers, like desktop computers, directly to a wall power outlet. However, they depend on batteries to allow portable use. Portable computers use one of three types of batteries – nickel-cadmium (Ni-Cad), nickel metalhydride (NiMH), or lithium-ion (Li-ion) batteries. Older portable computers used rows of Nickel-Cadmium (Ni-Cad) batteries, wired together to form an external, detachable device that could provide the required voltage and current. Ni-Cad batteries have an operating time of up to two hours and take a long time – up to 24 hours – to recharge. In addition, battery packs using Ni-Cad batteries often suffer from a charge/discharge cycle "memory effect" problem. This problem occurs when a battery is repeatedly charged and not fully discharged between charges. Its capacity to hold charge then diminishes, and the battery life becomes shorter. For these reasons, Ni-Cad battery packs are rarely used in newer computers. Newer portable computers use NiMH batteries, which are housed in a plastic case and are usually installed internally. These batteries have an operating time of up to two or three hours and take between two to three hours to recharge. As with NiMH batteries, Li-ion batteries are housed in a plastic case and are usually installed internally. They have an operating time of two to three hours and a recharge time of four to five hours. To maintain the performance of a portable computer, it is best to recharge a battery pack as soon as the system produces a "Battery low" warning. You should use an AC adapter for a portable computer whenever possible. This helps to conserve the battery – or keep it in a fully charged state – by applying a constant trickle charge to it. Portable memory PC cards Portable computers don't use standard memory modules or memory-expansion hardware. Some portable computers use single inline memory modules (SIMM) or dual inline memory modules (DIMM) for RAM. Other portable computers use small outline DIMMs (SODIMMs), proprietary memory modules, or PCMCIA memory-card modules for additional RAM. You should install only memory modules that the manufacturer of a portable computer recommends. Installing other types of memory may result in the system failing to recognize the RAM, resulting in short memory counts during the power-on self test (POST) routines. Short memory counts are when the POST does not recognize all the memory, and only counts or checks a part of it. It may also cause system failure, beep-coded error messages, soft memory errors – when the POST identifies errors with the new memory, and reports them – and failure of the operating system to boot. You need to ensure an appropriate voltage supply to memory devices in a portable computer. If the power supply to a memory device is insufficient, memory errors are likely to occur. To upgrade the memory in a portable PC, you need to disassemble its case and then replace the existing memory modules or add new ones.

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The position of the memory modules depends on the model of the computer, so you may need to check the manufacturer's instructions to locate them.

2. Upgrading HDDs If a system error message alerts you that the HDD is full, you should first use software disk utilities to optimize the organization of the space on the HDD. If this fails to free sufficient space, you should then remove any unnecessary programs and files from the HDD. You can store these programs and files on archival media, such as removable disks. For example, in Windows 2000, you use the Disk Cleanup utility to free space on the HDD. This utility first searches the HDD and then allows you to choose to delete unnecessary files, such as temporary files, Internet files, and unnecessary program files. Once unused disk space falls below 20 percent or the system is constantly waiting because the HDD is too slow, you need to upgrade the HDD or add a new HDD to the system. When you upgrade, you should ensure that the new HDD has a capacity that suits the needs of a system. For example, a system that has to support multimedia – intensive applications or to store large files requires a high- capacity HDD. When you install a new Enhanced Integrated Drive Electronics (EIDE) device with an older Integrated Drive Electronics (IDE) signal cable, the drive's operation is degraded to the level of the older drive. When you upgrade a drive from an IDE drive to an EIDE drive, you should check the capabilities of the system's ROM BIOS. If the system can't support large logical block addressing (LBA) or enhanced cylinders heads sector (ECHS) enhancements, the drive capacity of any hard drive will be limited to 504 megabytes (MB). HDD specifications that have a significant effect on system performance include   

access time data transfer rate track seek time

access time Access time – measured in milliseconds (ms) – is the average time that an HDD takes to position the read/write (R/W) heads over a track on a hard disk to locate a specific track sector. data transfer rate The data transfer rate – measured in megabytes per second (MBps) – is the speed at which information is transferred between the system and the HDD. track seek time Track seek time is the time that the HDD's read/write (R/W) heads take to move between the cylinders of a hard disk to locate the particular track that a seek command issued by the system identifies.

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3. Upgrading adapters and cooling systems To increase the speed of an Ethernet network, you can upgrade the Ethernet specification it uses. This involves upgrading the network interface cards (NICs) on PCs and installing the appropriate type of cable. The original Ethernet specification operates at 10 Mbps using coaxial cable, unshielded twisted pair (UTP) cable, or shielded twisted pair (STP) cable. By using UTP cabling in the network infrastructure, you can replace the 10 Mbps Ethernet NICs with 100 Mbps – Fast Ethernet – NICs.

Note 100 Mbps Ethernet is the most popular version of Ethernet in use today. It gives significant improvements in speed over the 10 Mbps Standard. The development of the graphic accelerator was an important advance in video card technology. This type of video card has its own processor, which significantly improves the speed of video-intensive applications, such as computer-aided design (CAD) or computer-aided manufacturing (CAM). A modem video card uses the Accelerated Graphics Port (AGP) slot for fast data transfer on the main system board. Three types of CPU cooling systems are   

heat sinks and cooling fans water coolers refrigeration

heat sinks and cooling fans A heat sink is a clip on device that pulls the heat away from the CPU, using fingers or fins that extend out from the base. A cooling fan maintains a temperature that will not damage the CPU. Heat sinks and cooling fans are generally the most common way of keeping a CPU cool. However, these methods don't provide sufficient cooling in all cases – if you need to overclock a CPU to its maximum, for instance. water coolers In a system that uses water cooling, a water pump sits inside the case and tubes move distilled water over the CPU to keep it cool. refrigeration With the refrigeration method of cooling, a refrigeration compressor sits inside the case of a CPU and reduces the temperature to around zero. For example, if the CPU runs at a speed that is higher than its recommended speed, it becomes hotter and needs more cooling than is available with conventional fans and heat sinks.

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Summary Portable computers use specialized peripheral devices that allow them to be small and lightweight. These devices include portable drives, PC cards, batteries, and portable memory PC cards. You should consider upgrading a hard disk drive (HDD) if available space on the disk falls below 20 percent or a system constantly waits to access information on it. HDD specifications that affect system performance include access time, data transfer rate, and track seek time. You can upgrade a 10 Mbps Ethernet network to use 100 Mbps or gigabit Ethernet by using an upgraded network interface card (NIC) and the appropriate type of cable. To improve the performance of video-intensive applications, you can install a specialized video card – the graphic accelerator – that has its own processor. It is also important to upgrade the cooling system for a PC in accordance with the heat it generates. Types of cooling systems include heat sinks and fans, water coolers, and refrigeration.

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