Chapter 4b(modern Cpu)

Chapter-4B Modern CPU

Microprocessor A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations. Three basic characteristics differentiate microprocessors:

• Instruction set: The set of instructions that the microprocessor can execute. • bandwidth : The number of bits processed in a single instruction. • clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.

Microprocessor

RISC Processor Pronounced risk, acronym for reduced instruction set computer, a type of microprocessor that recognizes a relatively limited number of instructions. Until the mid1980s, the tendency among computer manufacturers was to build increasingly complex CPUs that had everlarger sets of instructions. At that time, however, a number of computer manufacturers decided to reverse this trend by building CPUs capable of executing only a very limited set of instructions. One advantage of reduced instruction set computers is that they can execute their instructions very fast because the instructions are so simple. Another, perhaps more important advantage, is that RISC chips require fewer transistors, which makes them cheaper to design and produce

CISC PROCESSOR Stands for complex instruction set computer. Most personal computers, use a CISC architecture, in which the CPU supports as many as two hundred instructions.

Parallel Processing The simultaneous use of more than one CPU to execute a program. Ideally, parallel processing makes a program run faster because there are more engines (CPUs) running it. In practice, it is often difficult to divide a program in such a way that separate CPUs can execute different portions without interfering with each other. Most computers have just one CPU, but some models have several. There are even computers with thousands of CPUs. With single-CPU computers, it is possible to perform parallel processing by connecting the computers in a network. However, this type of parallel processing requires very sophisticated software called distributed processing software.

Multitasking In multitasking, only one CPU is involved, but it switches from one program to another so quickly that it gives the appearance of executing all of the programs at the same time.

Serial port A port, or interface, that can be used for serial communication, in which only 1 bit is transmitted at a time.

9 Pin Serial Port Connector Pin No. Function Pin No. Function 1 DCD (Data Carrier Detect) 6 DSR (Data Set Ready) 2 RX (Receive Data) 7 RTS (Request To Send) 3 TX (Transmit Data) 8 CTS (Clear To Send) 4 DTR (Data Terminal Ready) 9

Parallel port An output device that lets a computer transmit data to another device using parallel data transmission-that is, several bits sent simultaneously over separate wires. PC parallel ports are usually designated LPT1, LPT2, and so on

SCSI SCSI interfaces provide for faster data transmission rates (up to 80 megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.

USB Short for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps. A single USB port can be used to connect up to 127 peripheral devices, such as mice, modems, and keyboards. USB also supports Plugand-Play installation and hot plugging.

HOT Plugging The ability to add and remove devices to a computer while the computer is running and have the operating system automatically recognize the change. Two external bus standards -- Universal Serial Bus (USB ) and IEEE 1394 -- support hot plugging. Hot plugging is also called hot swapping.

IEEE 1394 A very fast external bus standard that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b). Products supporting the 1394 standard go under different names, depending on the company. Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link and Lynx, to describe their 1394 products. A single 1394 port can be used to connect up 63 external devices

MIDI . Computers that have a MIDI interface can record sounds created by a synthesizer and then manipulate the data to produce new sounds. For example, you can change the key of a composition with a single keystroke. A number of software programs are available for composing and editing music that conforms to the MIDI standard. They offer a variety of functions: for instance, when you play a tune on a keyboard connected to a computer, a music program can translate what you play into a written score.

Expansion Slot An opening in a computer where a circuit board can be inserted to add new capabilities to the computer. Nearly all personal computers except portables contain expansion slots for adding more memory, graphics capabilities, and support for special devices. The boards inserted into the expansion slots are called expansion boards, expansion cards , card , add-ins , and add-ons.

Expansion Board A printed circuit board that you can insert into a computer to give it added capabilities

PC CARD Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices.