Copyright © 2007 Heathkit Company, Inc. All Rights Reserved

PC Fundamentals

Presentation 17 Presentation 17 –– Buses Buses

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ObjectivesObjectives

At the end of this presentation, you will be able to:

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Define computer bus and explain its purpose.

Define the following terms: ISA, MCA, EISA, VL-Bus, PCI, PCI Express, and AGP.

Discuss the characteristics of the PCI, PCI Express, and AGP buses.

Recognize the connector (or slot) of an ISA, PCI, PCI Express, and VGA bus.

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CPUCPU

MemoryMemoryKeyboard ControllerKeyboard Controller

Parallel PortParallel Port

System ControllerSystem Controller

Video AdapterVideo

Adapter The Data BusThe Data Bus

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Keyboard ControllerKeyboard Controller

System ControllerSystem Controller

Video AdapterVideo

Adapter

CPUCPU

MemoryMemory

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MemoryMemory

Video AdapterVideo

Adapter

CPUCPU

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CPU Socket (Slot 1)

CPU Socket (Slot 1)

System Controller

System Controller

Bus Wires

Bus Wires

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What is a Bus?What is a Bus?

Signal Pathways

A way of passing information between components inside and outside the computer.

A modular way of expanding the functions or capabilities of the computer.

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PC Bus ArchitecturesPC Bus Architectures

ISA MCA EISA VL-Bus PCI AGP PCI Express

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The Original IBM PC BusThe Original IBM PC Bus

Introduced on the original IBM PC

8-bit data path

4.77-MHz clock

8 Interrupts – Only one of which was available for expansion boards.

4 DMA Channels – Only one of which was available for expansion boards.

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8-Bit Card8-Bit Card

8-Bit Slot8-Bit Slot

The Original IBM PC BusThe Original IBM PC Bus

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Industry Standard Architecture Industry Standard Architecture (ISA) Bus(ISA) Bus

Introduced on the IBM AT Computer 16-bit data path Backward compatible with IBM-PC Bus 8-MHz clock 15 Interrupts 7 DMA Channels

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16-Bit Card16-Bit Card

16-Bit Slot16-Bit Slot

Industry Standard Architecture (ISA) Bus

8-Bit Section Added Pins

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16-Bit Slot16-Bit Slot

Industry Standard Architecture (ISA) Bus

8-Bit Card8-Bit Card

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Micro-Channel Architecture (MCA) Micro-Channel Architecture (MCA) Bus Bus

Introduced on the IBM PS/2 16-bit or 32-bit data path 10-MHz clock Configured by software rather than by

jumpers or switches Not compatible with the ISA bus Bus Mastering

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Bus MasteringBus Mastering

Allows data to be passed from one device to another without CPU intervention.

Allows a controller card to take control of the bus, leaving the CPU free to concentrate on other tasks.

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Bus Mastering vs. DMABus Mastering vs. DMA

DMA can send data from peripheral to RAM or from RAM to peripheral, without the intervention of the CPU.

Bus Mastering can send data from peripheral to peripheral, without the intervention of the CPU.

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Extended ISA Bus (EISA)Extended ISA Bus (EISA)

The industry’s answer to the MCA bus

Backward compatible with ISA

16-bit or 32-bit data path

8-MHz Clock

Configured by software, not jumpers or switches

Bus Mastering

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CPUCPU

BUSController

BUSController

ISA BusSlots

ISA BusSlots

High SpeedCPU Bus

High SpeedCPU Bus

Low SpeedI/O BusLow SpeedI/O Bus

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CPUCPU

BUSController

BUSController

ISA BusSlots

ISA BusSlots

Local BusSlots

Local BusSlots

High SpeedCPU Bus

High SpeedCPU Bus

Low SpeedI/O Bus

Low SpeedI/O Bus

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VESA Local Bus (VL-Bus)VESA Local Bus (VL-Bus)

Clock speed same as the processor

32-bit data path

Regular ISA slot with local bus connector added

Bus Mastering

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Peripheral Component Interconnect Peripheral Component Interconnect (PCI)(PCI)

Developed for Pentium-class processors

32-bit and 64-bit data path versions

33-MHz Clock

Processor Independent

Plug and Play with Bus Mastering

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Peripheral Component InterconnectPeripheral Component Interconnect(PCI) Bus(PCI) Bus

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PCI EvolutionPCI Evolution

32-bit, 33 MHz 64-bit, 33 MHz 32-bit, 66 MHz 64-bit, 66 MHz

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PCI-X PCI-X

PCI-X 66 64-bit 66 MHz PCI-X 133 64-bit 133 MHz PCI-X 266 64-bit 266 MHz PCI-X 533 64-bit 533 MHz

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PCI ExpressPCI Express

The next generation of PCI. Serial data paths. Very high speed (2500 MHz) Scales easily as additional serial data

paths are added. X1 has one serial path, X4 four serial

paths, etc.

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PCI-Express @ 2500 MHzPCI-Express @ 2500 MHz

PCI Express x1 1 250 Mbps PCI Express x4 4 1000 Mbps PCI Express x8 8 2000 Mbps PCI Express x1616 4000 Mbps PCI Express x3232 8000 Mbps

Lanes Bandwidth

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PCI and PCI Express Slots PCI and PCI Express Slots

Conventional PCIConventional PCI

Conventional PCIConventional PCI

PCI Express X 16PCI Express X 16

PCI Express X 1PCI Express X 1

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Accelerated Graphics Port (AGP)Accelerated Graphics Port (AGP)

Developed for high speed graphics cards

Frees the PCI bus from making video transfers

Used only for video cards

Considered a port rather than a bus

66 MHz, 32-Bit

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Accelerated Graphics Port Accelerated Graphics Port (AGP)(AGP)

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AGP ModesAGP Modes32-bits @ 66 MHz32-bits @ 66 MHz

AGP 1 266 Mbps AGP 2X 2 533 Mbps AGP 4X 4 1066 Mbps AGP 8X 8 2133 Mbps

BandwidthData CyclesPer Clock

Copyright © 2007 Heathkit Company, Inc. All Rights Reserved

PC Fundamentals

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