Recipe 3.8. Resolving Device Conflicts


Problem

A device stops functioning after a new device is connected, or a newly connected device fails to function.

Solution

Using Device Manager

  1. To determine which devices have conflicts, click Start then right-click My Computer and select Properties.

  2. Select the Hardware tab, then click Device Manager.

  3. Review the list of device types for any expanded entries, and specifically individual devices marked with an exclamation point surrounded by a yellow dot. This indicates either a nonfunctioning device or a device with resources in conflict with another device.

  4. Double-click the device with the yellow exclamation point to access its properties.

  5. Select the Resources tab and note the entries under Resource Settings and the Conflicting Device List for details on the specific nature of the conflict. Most likely you will find a conflict between two COM ports, two LPT ports, or with a sound, video, or network card conflicting with another such device.

  6. You have the ability to change resource assignments for some devices if the Settings Based On, Use Automatic Settings, and Change Settings controls are not grayed out. There is an important distinction here you cannot change the resources a devices uses from within Windows. Doing so would violate Plug and Play and the Hardware Abstraction Layer rules. Here you can only tell Windows what the resources for the device are or will be once you reconfigure the device outside of Windows, and most likely by changing settings on the hardware itself with the system powered off and the device removed. Instead of making changes here and now, note which devices conflict, then reconfigure or remove the conflicting device and let Plug and Play determine the new configuration.

Using BIOS settings

  1. Restart your PC and press the appropriate key(s) to access the built-in BIOS setup program. Typically, pressing the DEL or F2 key will access setup, though some systems use F1, F10, Ctrl+Alt+S, or ESC.

  2. Within the BIOS setup program, locate the menu selection and entries for configuration of peripheral or I/O devices. This varies from PC to PC, make and model to make and model consult the documentation for your PC.

  3. There are several possible items to check, reconfigure, or reset the address and IRQ settings for COM and LPT ports, built-in/internal sound cards, and MIDI ports, assign or unassign IRQ for video, USB, or other devices that may present such options. Refer to Table 3-1 below for typical resource assignments for common I/O devices.

  4. After determining and setting a new configuration or AUTO mode, save your settings, exit setup, and restart your PC. The Plug and Play BIOS will detect the changes and refresh Windows' Device Manager accordingly.

Using hardware configurations

  1. Remove the conflicting hardware device.

  2. Consult the documentation for the device for options to reconfigure I/O addresses and IRQ assignments, then reconfigure the device for proper resource settings, referring to Table 3-1 below as appropriate.

  3. Replace the device in your PC.

  4. Restart your PC, and let Plug and Play detect the changes and update Windows.

Table 3-1. Common legacy I/O device resource settings

Device

I/O address

Interrupt / IRQ

COM1

3F8-3FFh

4

COM2

2F8-2FFh

3

COM3

3E8-3EFh

4

COM4

2E8-2EFh

3

LPT1

378-37Fh

7

LPT2

278-27Fh

5

Sound

220-2FFh

5, 10, 11

IDE Interface 1

1F0-1F7h

14

IDE Interface 2

170-177h

15


Discussion

In these days of Plug and Play devices it is rare, but not impossible, to have a resource conflict between two devices. Most conflicts are the result of installing an older-style modem or COM-port expansion card, an old SCSI card, or a sound card with improper settings. Even among Plug and Play devices, not all of them play well with others, and some simply will not respect the presence and configuration of devices already in the system. If two Plug and Play devices cannot resolve their conflicts by forcing a reset of NVRAM or Plug and Play settings through the BIOS, you may have to remove one of them and replace it with another make or model of device that behaves properly.

See Also

For a very complete and detailed discussion of legacy/non-Plug and Play hardware configurations, and how Plug and Play really works, obtain a copy of IRQ, DMA & I/O by Jim Aspinwall, and refer to the Plug and Play specification at http://www.microsoft.com/whdc/system/pnppwr/pnp/default.mspx.



Windows XP Cookbook
Windows XP Cookbook (Cookbooks)
ISBN: 0596007256
EAN: 2147483647
Year: 2006
Pages: 408

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