Bài giảng Computer - Chapter 08

Chapter Overview Understanding Expansion BusesConfiguring Expansion CardsCables and Connectors 1Understanding 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) 2Industry Standard Architecture (ISA)Standard established by IBMProblems with ISA design Lack of speedCompatibility problems 3Micro Channel Architecture (MCA)Was proprietary architecture designed by IBM to defend its market positionWas able to “self configure” devicesWas not backward compatible with ISA Had a 32-bit data pathHas been discontinued 4Extended ISA 5VESA Local Bus (VLB)6Peripheral Component Interconnect (PCI)Overcomes limitations of ISA, EISA, MCA, and VLBHas become an unofficial industry standardHas significant differences from VLB Are also differences in PCI versionsIs an evolving technology 7Accelerated Graphics Port (AGP)8IEEE 1394 (FireWire) Interface originally developed by AppleHigh-speed interface that allows up to 62 devices on a chainAdvantages: hot swap, inexpensive connectors, simple cable designDirect path to system memoryNot presently a widely used standard 9Universal Serial Bus (USB) Connects peripherals outside the computerSupports speeds of 1.5 Mbps for asynchronous transfer and 12 Mbps for isochronous transferOffers the following advantages: Hot swapRecognition of new device by operating system (OS)Ease of adding new devices 10The Most Common I/O Addresses 11Setting 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. 12Interrupt Request (IRQ) 13Cascading the 8259 Chip 14Setting IRQs Set IRQs during installation.Use hardware, software, or a combination of both to set IRQs.Document all IRQ settings. 15Direct 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. 16Setting and Managing DMA Channels ECP = Extended Capabilities PortSCSI = Small Computer System Interface17COM and Ports 18COM 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. 19LPT 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. 20Installing Expansion Cards Read the documentation.Document addresses and DMA and IRQ settings.Keep settings unique, and document them. 21Parallel Printer Cables 22IEEE 1284 Printer Modes It is important to configure the correct mode for each printer.Each pin assignment corresponds to a specific function. 23Serial Port Cables 24Null Modem and SCSI Cables Null modem cable: used to directly connect two computersSCSI cable: used to connect a variety of internal and external devices 25Keyboard Cables 26Identifying Cables and Connectors CommunicationPrinterMonitorGame portKeyboard 27Troubleshooting 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. 28Summary of Connectors DB-9, DB-25: used for serial and parallel port communications, respectivelyRJ-11, RJ-12: standard telephone connectorsRJ-45: network connectorPS/2 (mini-DIN): supports mouse, scanners, and some keyboardsCentronics: supports printersUSB: supports a variety of peripheral devices 29Chapter 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. 30