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Chapter Overview

Chapter Overview. Understanding Expansion Buses Configuring Expansion Cards Cables and Connectors. Understanding Expansion Buses. A system bus is the series of connections between the CPU and the system memory. An expansion bus connects add-on devices to the computer system.

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Chapter Overview

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  1. Chapter Overview • Understanding Expansion Buses • Configuring Expansion Cards • Cables and Connectors

  2. Understanding Expansion Buses • A system bus is the series of connections between the CPU and the system memory. • An expansion bus connects add-on devices to the computer system. • Expansion buses include the following types: • Industry Standard Architecture (ISA), Micro Channel Architecture (MCA), Extended Industry Standard Architecture (EISA) • VESA local bus (VLB), Peripheral Component Interconnect (PCI), Accelerated Graphics Port (AGP) • Institute of Electrical and Electronics Engineers (IEEE) 1394 (FireWire), universal serial bus (USB)

  3. Industry Standard Architecture (ISA) • Standard established by IBM • Problems with ISA design • Lack of speed • Compatibility problems

  4. Micro Channel Architecture (MCA) • Was proprietary architecture designed by IBM to defend its market position • Was able to “self configure” devices • Was not backward compatible with ISA • Had a 32-bit data path • Has been discontinued

  5. Extended ISA

  6. VESA Local Bus (VLB)

  7. Peripheral Component Interconnect (PCI) • Overcomes limitations of ISA, EISA, MCA, and VLB • Has become an unofficial industry standard • Has significant differences from VLB • Are also differences in PCI versions • Is an evolving technology

  8. Accelerated Graphics Port (AGP)

  9. IEEE 1394 (FireWire) • Interface originally developed by Apple • High-speed interface that allows up to 62 devices on a chain • Advantages: hot swap, inexpensive connectors, simple cable design • Direct path to system memory • Not presently a widely used standard

  10. Universal Serial Bus (USB) • Connects peripherals outside the computer • Supports speeds of 1.5 Mbps for asynchronous transfer and 12 Mbps for isochronous transfer • Offers the following advantages: • Hot swap • Recognition of new device by operating system (OS) • Ease of adding new devices

  11. The Most Common I/O Addresses

  12. Setting and Managing I/O Addresses • Non–Plug and Play I/O addresses are set with jumpers, dual inline package (DIP) switches, and software drivers. • Plug and Play devices are self-configuring and can conflict with older non–Plug and Play cards. • Devices with overlapping I/O addresses will not respond to commands.

  13. Interrupt Request (IRQ)

  14. Cascading the 8259 Chip

  15. Setting IRQs • Set IRQs during installation. • Use hardware, software, or a combination of both to set IRQs. • Document all IRQ settings.

  16. Direct Memory Access • The direct memory access (DMA) chip (8237) offloads work from the CPU. • Each 8237 chip supports four devices. • Two DMA chips are cascaded to provide eight DMA channels.

  17. Setting and Managing DMA Channels ECP = Extended Capabilities Port SCSI = Small Computer System Interface

  18. COM and Ports

  19. COM Ports • COM1 and COM3 share IRQ4. • COM2 and COM4 share IRQ3. • COM3 uses I/O port 3E8–3EF and COM1 uses 3F8–3FF. • COM4 uses I/O port 2E8–2EF and COM2 uses 2F8–2FF.

  20. LPT Ports • You should use IRQ7 for LPT1 and IRQ5 for LPT2. • IRQ5 is typically used by sound cards. • Devices other than printers can use LPT ports. • The USB is taking over many of the parallel designs.

  21. Installing Expansion Cards • Read the documentation. • Document addresses and DMA and IRQ settings. • Keep settings unique, and document them.

  22. Parallel Printer Cables

  23. IEEE 1284 Printer Modes • It is important to configure the correct mode for each printer. • Each pin assignment corresponds to a specific function.

  24. Serial Port Cables

  25. Null Modem and SCSI Cables • Null modem cable: used to directly connect two computers • SCSI cable: used to connect a variety of internal and external devices

  26. Keyboard Cables

  27. Identifying Cables and Connectors • Communication • Printer • Monitor • Game port • Keyboard

  28. Troubleshooting Cables • Always check the cable first. • Always check for loose connections. • Check for bent or broken pins. • Do not use force. • Check for worn or frayed cables. • Ensure that you are using the correct cable. • Avoid “homemade” cables.

  29. Summary of Connectors • DB-9, DB-25: used for serial and parallel port communications, respectively • RJ-11, RJ-12: standard telephone connectors • RJ-45: network connector • PS/2 (mini-DIN): supports mouse, scanners, and some keyboards • Centronics: supports printers • USB: supports a variety of peripheral devices

  30. Chapter Summary • Expansion buses are standardized connections for installing devices. • Expansion buses have several architecture types. • All devices require unique I/O addresses, IRQs, and DMA channels. • IRQ conflicts cause most problems during installation of a new device. • COM ports are used for serial devices, and LPT ports are used for parallel devices. • It is important to identify cables and connectors. • Loose or poorly connected cables often cause computer problems.

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