PC Hardware

Installing Expansion Cards

The rules for installing expansion cards are simple:

  • First read the manual.

  • Document addresses and DMA and IRQ settings for any non-Plug and Play device.

  • Keep the IRQs, DMAs, and I/O addresses unique.

Windows 95, Windows 98, and Windows 2000 support Plug and Play. In most cases, you can insert a Plug and Play card into the proper type of expansion slot and turn on the computer. Windows will find the card and guide you through the setup. The savvy computer professional documents and keeps track of the IRQ, DMA, and I/O addresses, in case a conflict arises with a Plug and Play device on the system.

Windows 95 and Windows 98 use Hardware Properties, under the System Information/Device Manager option in the Control Panel, which does a good job of identifying (and allowing) changes to these settings.

A good way to document a computer is to print a complete list of the computer's hardware settings from this Hardware Properties dialog box.
For Plug and Play to work, the computer must have a Plug and Play BIOS, and the operating system and the device card must be Plug and Play-compliant.

Lesson Summary

The following points summarize the main elements of this lesson:

  • Every device in a computer needs a unique name and address.

  • In order for the CPU to identify which devices need to use the data bus, it monitors the IRQs.

  • Generally, no two devices can use the same IRQ or DMA channel.

  • Most conflicts during an installation of a new device are caused by IRQ conflicts.

  • BIOS routines or device drivers can use I/O addresses to initiate "conversations" over the external data bus by means of an interrupt request (IRQ).

  • DMA handles all the data passing from peripherals to RAM and vice versa.

  • COM ports are for serial devices; LPT ports are for parallel devices.

  • The computer technician should document addresses and DMA and IRQ settings for any non-Plug and Play device installed in a computer.