9 Bus Architecture

BUS ARCHITECTURE A set of parallel conductors, which allow devices attached to it to communicate with the CPU is called BUS. It allows information and signals to travel between components. The bus consists of three main parts • Control Lines • Address Lines • Data Lines

Control lines •

These allow the CPU to control which operations the devices attached should perform, I.E. read or write.

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These are used to synchronize and co ordinate the operation of CPU with other devices .

Address lines •

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Allows the CPU to reference certain (Memory) locations within the device. Specifies the location of the device . The number of bits in the address bus represents the number of physical

Data lines •

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The meaningful data which is to be sent or retrieved from a device is placed on to these lines. The size of a data bus is typically 8, 16, 32, and

Microprocessor is attached to the devices with the help of three buses

• The Bus is set to run at a specified speed which is measured in MHz . • • The main differences among buses are amount of data transfer & the speeds so BUS is always differentiated or given a different name on the basis of their speed, devices with which BUS is

CPU, front side and back side bus

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The System Bus •

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The system bus is a series of high-bandwidth pathways that connect the CPU to memory, the level 2 (L2) cache and the I/O buses. The purpose of the system bus is to get information to and from the CPU at the fastest rate possible. As a result, the system bus is the fastest bus in the computer, with speeds up to 800 MHz on current motherboards.

systems bus actually • The consists of several buses, connected by several controller chips as follows: • The front side bus is actually a combination of 2 other buses: • The processor bus is the highestlevel communication pathway between the CPU and the Northbridge chip; • The memory bus is a direct pathway between the memory

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The backside bus is a special bus that connects the CPU to the level 2 (L2) cache. (Both of which are often packaged together in the same module). 

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As a result, this bus is also called the cache bus. Unlike the rest of the system bus components, the cache bus is a dedicated bus that runs at or near the CPU speed, achieving

Understanding buses

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When buses terminates on the motherboard ,a slot/port is placed to provide connectivity between bus and the card which will be attached with the slot and as a result a path will be provided from circuit to CPU with the help of BUS.

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Various developments took place in terms of speed and width of bus i.e. 16bit, 32 bit etc and accordingly they were given different name.

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The slot that is placed on the bus to provide connectivity is known as

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Data width & Cycle The data rate width and cycle rate are used to determine the bandwidth, or the total amount of data that the bus can transmit.

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An 8-bit bus (1-byte data width) that operates at a cycle rate of 1,000 MHz (1,000,000

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Device management & Type The device-management specification indicates the maximum number of supported devices and the difficulty of configuring them. There are two types of bus communications, serial and parallel. On a parallel bus, all devices have their own interface to the bus, which is the norm. Serial devices are tied together in, well, a series; the last one has to talk “through” the first one.

VARIOUS TYPES OF BUSES

Introduction with various Expansion BUS/slots

• Expansion

slots

are compartments in a PC into which you can plug Expansion Cards such as a video or sound card & connect them to the system bus.

• • Most PC's have from 3 to 8

• Expansion slots for PCs come in two basic sizes: half- and full-size. • Half-size slots are also called 8-bit slots because they can transfer 8 bits at a time. • Full-size slots are sometimes called 16-bit slots. In addition, modern PCs include PCI slots for

• An expansion card in computing is a printed circuit board that can be inserted into an expansion slot of a computer motherboard to add additional functionality to a computer system. • • One edge of the expansion card holds the contacts that fit exactly into the slot. • • They establish the electrical

ISA Expansion slots • Industry Standard Architecture (in practice almost always shortened to ISA) was a computer bus standard for IBM compatible computers. •

• introduced in 1981 with original IBM PC

ISA Slots

• Starting in the early 90s, ISA began to be replaced by the PCI local bus architecture. • Most computers made today include both an AT bus for slower devices and a PCI bus for devices that need better bus performance. • In 1993, Intel and Microsoft introduced a new version of the ISA specification called Plug and Play ISA. • Plug and Play ISA enables the operating system to configure expansion boards automatically so that users do not need to fiddle with DIP switches and jumpers.

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Micro Channel Architecture(MCA)

proprietary 16- or 32-bit parallel computer bus created by IBM in the 1980s for use on their new PS/2 computers. MCA was primarily a 32-bit bus, but the system also supported a 16-bit mode designed to lower the cost of connectors and logic in Intelbased machines like the IBM

MCA Card

EISA •

Extended Architecture

Industry

Standard

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Bus architecture designed for PCs using an Intel 80386, 80486, or Pentium microprocessor.

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EISA buses are 32 bits support multiprocessing.

wide

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The principal difference between EISA and MCA is that EISA is backward

EISA Slots

PCI Expansion Slots Peripheral Component • The Interconnect(PCI) • computer bus for attaching peripheral devices to a computer motherboard. • • Typical PCI cards used : • • network cards, sound cards, modems, extra ports such as

PCI Slots

• Many common PCI card devices are now integrated into motherboards • It can run at clock speeds of 33 or 66 MHz at 32 bits, it yields a throughput rate of 133 Mbps. • In a typical system, the firmware (or operating system) queries all PCI buses at startup time (via PCI Configuration Space) to find out what devices are present and what system resources (memory space, I/O space, interrupt lines, etc.) each needs.

PCI Express • PCI Express, officially abbreviated as PCI-E or PCIe, • computer expansion card interface format introduced by Intel in 2004. • PCI Express was designed to replace the general-purpose PCI expansion bus, the high-end PCI-X bus and the AGP graphics card interface. • In PCI 1.1 (currently the most common version) each lane sends information at a rate of 250 MB/s (250 million bytes per second) in

PCIeX4, PCIeX16, PCIeX1, PCIeX16 and PCI

• Each PCIe slot carries either one, two, four, eight, sixteen or thirty-two lanes of data between the motherboard and the card. • Lane counts are written with an x prefix e.g. x1 for a single-lane card and x16 for a sixteen-lane card. • Thirty-two lanes of 250 MB/s (PCIe 1.1) gives a maximum transfer rate of 8 GB/s (250 MB/s x 32, i.e., 8 billion bytes per second) in each direction. • However the largest size in common use for PCIe 1.1 is x16, giving a transfer rate of 4 GB/s (250 MB/s x 16) in each direction. • Single lane for PCIe 1.1 has nearly twice the data rate of normal PCI, a four-lane slot has a transfer rate

A 32- bit PCI card

AGP Expansion Slots • • • •

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Accelerated Graphics Port Interface specification developed by Intel Corporation. AGP is based on PCI, but is designed especially for the throughput demands of 3-D graphics. Rather than using the PCI bus for graphics data, AGP introduces a dedicated point-to-point channel so that the graphics controller can directly access main memory. 32 bits wide and runs at 66 MHz. This translates into a total bandwidth of 266 MBps; as opposed

An AGP Slot

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In addition, AGP allows 3-D textures to be stored in main memory rather than video memory.

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AGP has a few important system requirements as: • The chipset must support AGP. • The motherboard must be equipped with an AGP bus slot or must have an integrated AGP graphics system. • The operating system must be the OSR 2.1 version of Windows 95, Windows 98 or Windows NT 4.0. And currently, many professional •

PCMCIA • Personal Computer Memory Card International Association. • Designed to provide a way of expanding the memory in a small, handheld computer. • The PCMCIA was organized to provide a standard way of expanding portable computers. • The PCMCIA bus has been recently renamed as PC card. • Three major types of PC cards (and slots) in use today. • Type I-commonly used for memory cards,

A P C M C IA C a rd

PCMCIA Slots

Universal Serial Bus

• Any computer comes with one or more Universal Serial Bus connectors on the back. • These USB connectors let you attach everything from mice to printers to your computer quickly and easily. • The operating system supports USB • USB devices are incredibly simple. • Many USB devices are present in the market • The Universal Serial Bus gives you a single, standardized, easy-to-use

Various types of USB connectors

USB Features • The computer acts as the host. • Up to 127 devices can connect to the host, either directly or by way of USB hubs. • Individual USB cables can run as long as 5 meters; switch hubs, devices can be up to 30 meters (six cables' worth) away from the host. • With USB 2.0, the bus has a maximum data rate of 480 megabits per second. • A USB cable has two wires for power

USB Features • On the power wires, the computer can supply up to 500 milliamps of power at 5 volts. • Low-power devices (such as mice) can draw their power directly from the bus. High-power devices (such as printers) have their own power supplies and draw minimal power from the bus. Hubs can have their own power supplies to provide power to devices connected to the hub. • USB devices are hot swappable, meaning you can plug them into the bus and unplug them any time.

AMR and CNR §

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Some newer motherboards feature a special connector called an Audio Modem Riser (AMR) or a Communication and Networking Riser (CNR). These are dedicated connectors for cards that are specific to the motherboard design to offer communications and networking options. They are not designed to be general-purpose bus interfaces,

Riser slot on motherboard marked by red lines

Audio Modem Riser • Audio Modem Riser (AMR) is a specification developed by Intel for packaging the analog I/O audio functions of modem circuitry together with a CODEC chip (which converts back and forth from analog to digital) on a small board that plugs directly into a computer's motherboard. • The small board is called a riser because it rises above the motherboard rather than laying flatly on it. • Having this circuitry on a riser means that it doesn't have to be part of the motherboard itself.

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Communication and Networking Riser Communication and Networking Riser (CNR),

which was developed by Intel, is an open industry standard for a scalable riser card, which is a hardware device that plugs into a motherboard and holds chips for functions like modems and audio devices. • The CNR architecture and electrical, mechanical, and thermal requirements of the riser interface are defined in the specification. • The specification was developed for products used to implement low-cost local area network (LAN), modem, and audio subsystems and supports broadband, multichannel audio, V.90 analog modem, and Ethernet-based networking, and can be expanded upon to meet the requirements of developing technologies, such as DSL. • In addition to cost benefits, CNR has the capacity to minimize electrical noise

Riser socket

Fire wire IEEE 1394 • IEEE 1394, High Performance Serial Bus, for connecting devices to your personal computer. • FireWire provides a single plug-andsocket connection on which up to 63 devices can be attached with data transfer speeds up to 400 Mbps (megabits per second). • The standard describes a serial bus or pathway between one or more peripheral devices and your computer's microprocessor.

F ire w ire co n n e cto rs

Fire wire sockets

• FireWire and other IEEE 1394 implementations provide: • A simple common plug-in serial connector on the back of your computer and on many different types of peripheral devices A thin serial cable rather than the thicker parallel cable you now use to your printer, for example • A very high-speed rate of data transfer that will accommodate multimedia applications (100 and 200 megabits per second today; with much higher rates later) • Hot-plug and Plug and Play capability without disrupting your computer • The ability to chain devices together in a number of different ways without

• • In time, IEEE 1394 implementations are expected to replace and consolidate today's serial and parallel interfaces, including Centronics parallel, RS232C, and Small Computer System Interface (SCSI). • The first products to be introduced with FireWire include digital cameras, digital video disks (DVDs), digital video tapes, digital camcorders, and music systems. • Because IEEE 1394 is a peer-to-peer interface, one camcorder can dub to another without being plugged into a computer.

Fire wire socket in a DV camcorder

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