Resolving Resource Conflicts

The resources in a system are limited. Unfortunately, the demands on those resources seem to be unlimited. As you add more and more adapter cards to your system, you will find that the potential for resource conflicts increases. If your system is fully PnP-compatible, potential conflicts should be resolved automatically, but often are not.

How do you know whether you have a resource conflict? Typically, one of the devices in your system stops working. Resource conflicts can exhibit themselves in other ways, though. Any of the following events could be diagnosed as a resource conflict:

  • A device transfers data inaccurately.

  • Your system frequently locks up.

  • Your sound card doesn't sound quite right.

  • Your mouse doesn't work.

  • Garbage appears on your video screen for no apparent reason.

  • Your printer prints gibberish.

  • You can't format a floppy disk.

  • The PC starts in Safe mode (Windows 9x/Me) or can start only in Last Known Good Configuration (Windows 2000/XP).

Windows 9x/Me and Windows 2000/XP also show conflicts by highlighting a device in yellow or red in the Device Manager representation. By using the Windows Device Manager, you can usually spot the conflicts quickly. One way to resolve conflicts is to help prevent them in the first place.

Especially if you are building up a new system, you can take several steps to avoid problems. One is to avoid using older ISA devices. By definition, they cannot share IRQs, and that is the resource most in demand. PCI (and AGP) cards can share IRQs with IRQ Steering and as such are a much better choice.

Another way you can help is to install cards in a particular sequence, and not all at once. Modifying the installation sequence often helps because many cards can use only one or two out of a predefined selection of IRQs that is specific to each brand or model of card.

By installing the cards in a controlled sequence, the plug-and-play software can more easily work around IRQ conflicts caused by the default configurations of different cards. The first time you start up a new system you have assembled or done major upgrades on, the first thing you should check is the BIOS Setup.

If you have a setting for PnP Operating System in your BIOS, be sure it is enabled if you are running an operating system with plug-and-play support, such as Windows 9x/Me/2000/XP. Otherwise, make sure it's disabled if you are running an OS that is not plug-and-play, such as Windows NT.

On initial startup I recommend a minimum configuration with only the graphics card, memory, and storage drives (floppy, hard disk, CD-ROM, and DVD). This allows for the least possibility of system conflicts in the initial configuration.

If your motherboard came with a CD including drivers specific to the chipset or other built-in features of the board, now is the time to load or install them. Complete the configuration of all built-in devices before installing any other cards or external devices.

After the basic system has been configured (and after you have successfully loaded your operating system and any updates or patches), you can then begin adding one device at a time in a specific order. So, you will power down, install the new device, power up, and proceed to install any necessary drivers and configure the device.

You'll probably have to restart your system after you are done to fully complete the configuration. Here's the loading sequence for additional cards:

  1. Sound card

  2. Internal or external modem

  3. Network card

  4. Auxiliary video devices, such as MPEG decoders, 3D accelerators, and so on

  5. SCSI adapter

  6. Anything else

Normally, using this controlled sequence of configuring or building up your system results in easier integration with less conflicts and configuration hassles.