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[ The PC Guide | Systems and Components Reference Guide | Motherboard and System Devices | System Resources | System Configuration ]

Assigning Resources to Devices

Many devices have fixed resource assignments that cannot be changed. Most system devices are like this. In addition, it is generally best not to change (or try to change) the resource settings for standard devices like IDE hard disk controllers unless you both really know what you are doing and there is a compelling reason to change them. The following devices usually have hard-coded resource settings that cannot be changed: system devices, keyboard, PS/2 mouse, floppy disk controller, primary IDE controller, video card. Others can generally be changed, although it makes more sense for some devices than for others.

There are several different ways that are generally used to set or change resource settings for devices:

  • Hardware Settings: Resource assignments on some cards, especially older ones, is done by hardware on the device itself. This involves changing the settings of jumpers and switches, usually on the circuit board of the device, to tell it what resources to use. This is similar to the way most motherboards are configured. Hardware configuration has the great disadvantage of being a pain if you ever want to change the resources: you have to open the box and usually pull out the card to get to the jumpers. It has one great advantage however: certainty. You always know that if you put the jumper on say IRQ7, the card will try to use IRQ7 (if it isn't busted of course. :^) ) You can always open the box and look at the card and get visual confirmation of how it is set up. You cannot do this with software-based configuration.
  • Software Configuration Programs: Many newer cards are configured using special software config programs that come with them. You run the program and select the resources you want to use, and the program writes the information into a special rewriteable EEPROM placed on the device for that purpose. This is similar to the way a flash BIOS is used to upgrade the system BIOS using software, on a smaller scale.
    Devices that use configuration programs like these are much more convenient than those that use hardware settings, because you can change the resources without opening the box. However, they have the disadvantage of being dependent on the configuration program; if you lose the disk you'll need to get another copy of the program to change the settings. You also can't tell what the settings are with the power off, and you run the slight risk of scrambling the card's settings if you say, lose power while it writes new settings to the card.
  • Plug and Play: Newer devices that subscribe to the Plug and Play standards can be automatically configured under certain conditions when used in a machine that supports Plug and Play, with an operating system that supports it. Plug and Play is an attempt to eliminate the large amount of work in assigning resources to devices and resolving conflicts. When it works properly, resources are dynamically and automatically assigned and reassigned and you don't have to worry about making everything work together.
    In addition, the use of a PnP operating system like Windows 95 will normally allow you to change device resource settings using the built-in Device Manager, giving you override control if you don't like what PnP chose for your device, and eliminating the need for special configuration utilities. However, often problems result from the system making poor resource choices or having difficulties dealing with devices in the system that are not themselves PnP-compatible.

Tip: It is always a good idea, once you have your system configured in a way that makes sense and works for you, to record the system configuration for future reference.

Next: Problems With Changing Default Resource Assignments

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