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Bus structures

Unit objectives Describe the primary types of buses Define interrupt, IRQ, I/O address,

DMA, and base memory address Describe the features and functions of

the PCI bus, and install and configure a PCI adapter card

Describe the features and functions of the various video buses, and install and configure an AGP adapter card

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Topic A

Topic A: Buses Topic B: Host system interaction Topic C: The PCI bus Topic D: Video buses

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Buses

Communication pathway Four types

– Address– Data– Expansion– Video

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PCI bus slots

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An AGP video bus slot

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The riser bus

Brings the basic wiring and control of a function to a motherboard

Decreases cost Three riser standards:

– Advanced Communication Riser (ACR) – Audio/Modem Riser (AMR) – Communication and Networking Riser

(CMR)

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Activity A-1

Examining buses

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Topic B

Topic A: Buses Topic B: Host system interaction Topic C: The PCI bus Topic D: Video buses

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System interaction

Gain the attention of the CPU Access shared memory locations Extend the system BIOS Transfer data across the bus

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Interrupts

Signal CPU that attention is needed– CPU stops what it was doing– Services the device request– Returns to its previous task

Polling– Inefficient alternative to interrupts

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Running processes

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IRQs

Numerical addresses Help CPU identify interrupt source Enforce priority of interrupts Common IRQs

– IRQ 1: Keyboard– IRQ2: Cascade IRQs 9-15– IRQ4: COM1– IRQ6: Floppy– IRQ12: PS/2 mouse– IRQ14: Primary IDE hard drive

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Assigning IRQs

Manually assign for older PC designs– DIP switches– Jumpers– Proprietary software

Common for conflicts Plug and Play (PnP) in new PC

designs

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Device Manager - IRQs

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Activity B-1

Examining running processes and IRQ assignments

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I/O addresses

Identify section of shared memory Range of memory addresses Hexadecimal

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Device Manager–I/O addresses

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Activity B-2

Viewing your computer’s I/O address assignments

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DMA channels

DMA controller relieves CPU DMA channels Largely replaced by other techniques

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Device Manager–DMA channels

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Activity B-3

Viewing your computer’sDMA channel assignments

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Base memory addresses

Starting memory address of BIOS extensions– Display adapters– SCSI controllers– IDE controllers

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Device Manager–Base memory

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Activity B-4

Viewing your computer’s base memory address assignments

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Topic C

Topic A: Buses Topic B: Host system interaction Topic C: The PCI bus Topic D: Video buses

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PC/XT bus

8-bit bus– IBM PC and IBM XT

4.77 MHz clock speed 1.6 Mbps maximum data transfer rate

(0.4 MBps) Supported IRQs 0-8 Configured with DIP switches or

jumpers

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PC/XT card

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DIP switches and jumpers

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PC/AT and ISA bus

16-bit bus– IBM AT, clones, 80386/486, current PCs

8 MHz clock speed 8 MBps maximum data transfer rate

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ISA adapter

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ISA expansion bus slot

ISA slot

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PCI bus

32- or 64-bit bus– Pentium PCs

33 or 66 MHz clock speed 133-533 MBps maximum data transfer

rate Up to 8 functions on a single card Up to 5 card/slots per system Requires PnP

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PCI adapter

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PCI slots

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PCIe

Newer standard Uses serial communication Link Lanes x1 (by-one) x1, x2, x4, x8, x12, x16, and x32 bus

widths Can up-plug Can’t down-plug

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Activity C-1

Installing a PCI card

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Topic D

Topic A: Buses Topic B: Host system interaction Topic C: The PCI bus Topic D: Video buses

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Need for video buses

Older PC designs just used expansion bus

Graphical interfaces involve massive amounts of graphics data

Specialized buses developed to be fast enough

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VESA local bus

32- or 64-bit bus– Pentium PCs

33 or 66 MHz clock speed Popular on 80486-based PCs Generally software configurable No longer used

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VLB adapter

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AGP adapter

Note the hook

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AGP

Technically a port, not a bus 32-bit bus 33 or 66 MHz clock speed Speed “pumped” to as much as 533

MHz DIrect Memory Execute (DIME) 266-2133 MBps maximum data

transfer rate PnP configurable

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Activity D-1

Installing an AGP adapter

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Unit summary

Described the primary types of buses Defined interrupt, IRQ, I/O address,

DMA, and base memory address Described the features and functions

of the PCI bus, and installed and configure a PCI adapter card

Described the features and functions of the various video buses, and installed and configure an AGP adapter card