Bus

A bus is an interface between a generic computer and a specific adapter that you install.

Interacting with the Host System

Adapters, as well as other hardware and applications, must communicate with the host system in an orderly and established way.

Communication must be orderly to avoid setting conflicts when configuring adapters to gain the attention of the host processor.

Conflicts are a main cause of problems in communication between adapter and host systems.

Hardware Resource

A hardware resource is a uniquely assigned communications path that enables a device to exchange information with the CPU and operating system.

IRQ 8-bit Defaults 16-bit Defaults

0 System timer System timer

1 Keyboard Keyboard

2 Available Cascade to IRQ9

3 COM2 COM2 & COM4

4 COM1 COM1 & COM3

5 Hard disk controller LPT2

6 Floppy disk drive controller Floppy disk drive controller

7 LPT1 LPT1

8 Real Time Clock (RTC)

9 Cascade to IRQ2

10 Available

11 Available

12 Bus mouse port

13 Math coprocessor

14 Hard disk controller

15 Available

IRQ Assignments

I/O Addresses

Base Memory Addresses

Direct Memory Addresses

Configuring System Parameters

You configure cards with jumper pins by using the jumpers, which are plastic-coated metal clips, to close a circuit represented by a bank or group of jumper pins. If a jumper goes bad, the circuit will not be completed until the jumper is replaced. One way to save jumpers so that they are available for replacement is to place them over only one of the jumper pins in a pair.

Switches are usually found in even-numbered banks or groups. You configure cards with switches by using a small object such as a mini-screwdriver, pen pint, or bent paper clip to set the switches to ON or OFF. Do not use a pencil to set switches—the graphite can get into and foul the switch mechanism.

Viewing Resource Settings in Device Manager

Plug and Play

You connect a piece of hardware to a PnP-compatible system running a PnP-aware operating system.

All PnP cards enter Configuration mode by enabling PnP code built into the card.

One at a time, PnP cards are isolated and a handle is assigned to the card. The handle is used to identify that card.

Resources are allocated to each card that don’t conflict with resources allocated to any other card.

All PnP cards are activated and exit Configuration mode.

An 8 bit Expansion Card

ISA

16-bit ISA card

8-bit ISA card

ISA slotsISA slots

ISA edge connectorsISA edge

connectors

EISA Card

Extra notches for alignmentExtra notches for alignment Double row of edge connectorsDouble row of edge connectors

Notch matches ISA notchNotch matches ISA notch

The 32-Bit Microchannel Bus Connection with a Video Extension

Videoextension

Videoextension

PCI

PCI slotsPCI slots

PCI edge connectorPCI edge connector

VL-Bus Connection on an Adapter

AGP

AGP video cardAGP video cardAGP slotAGP slot

Symptom Possible Problem Solution

Adapter seems to work fine until you replace the system case.

Adapter card is grounded against the case.

Visually inspect card and case for bent or damaged areas. If the card is in contact with the case, it can cause electrical shorts or other faults.

Card works fine in another slot, but when any card is inserted in this particular slot, it doesn’t work.

Bus slot damaged.

Visually inspect the bus slot. Test the bus slot with a multimeter; voltages should be within prescribed ranges for the slot and adapter card.

Card tests fine and slot tests fine, but services are unavailable.

Cables not connected, loose, or damaged.

Visually inspect cards and cables and reconnect if necessary.

Services provided by the adapter or a device connection to the adapter work intermittently.

Adapter card (or cards) not seated properly.Hardware resource conflict.Adapter card physically damaged.Adapter card electronically damaged.

Replace any adapter card that is physically damaged.Replace any adapter card that is electronically damaged.

Common Problems with Adapter Cards