Identifying and fixing IRQ sharing conflicts
Written by: pcAudioLabs.com

IRQ sharing conflicts can cause numerous problems with digital audio playback such as Pops, Clicks, Stutters, Freezes, and Error Messages. IRQ stands for Interupt Request. For each CPU in a computer, there are 15 IRQs. Each device is assigned an IRQ by the Motherboard and/or Windows. In Windows 98/ME/2000/XP there is a utility called msinfo32.exe that is used to identify if your computer has an IRQ sharing conflict. Click on the START button and select RUN. Type in the word msinfo32.exe (You can also access msinfo32.exe by clicking on the START > PROGRAMS > ACCESSORIES > SYSTEM TOOLS > SYSTEM INFORMATION). In the left side of the msinfo32.exe window, Click on the + sign next to Hardware Resources. Below Hardware Resources, select IRQs. In the left side of the screen find your Sound Card in the list. Just to the left of the Sound Card is the IRQ number. Your computer has an IRQ sharing conflict If the same number appears with another device such as the Graphics Card, Network Card, or SCSI controller card. If there is IRQ sharing with something called 'ACPI holder for PCI steering', this is not considered a conflict.


Above you can see that the Creative SB Live! Value (WDM) is using IRQ 3 and has no sharing conflict. However, 3dfx Voodoo3 on IRQ 11 has a sharing conflict with the Adaptec AIC-7895 Dual Ultra SCSI device.



There are 3 ways to fix an IRQ sharing conflict.
-1. Turn off the computer and unplug the power cable. Open up the computer case and physically remove the card from the motherboard and place it into a different PCI slot. Check msinfo32.exe for changes.
-2. Enter the Motherboard BIOS setup (Refer to your Computer or Motherboard's User Manual for specific instructions on how to enter the Motherboard BIOS). Select PnP/PCI configuration in the BIOS setup. In the following screen, there should be selections to switch to a Non PnP OS and to manually assign IRQ to PCI slots. Refer to the Motherboard manual regarding the assignment of IRQ per PCI slot.
-3. In the Motherboard BIOS, you can disable any Devices or Ports on your computer that you do not use. Some examples include COM ports 1 & 2, Built in Audio, and even USB. By disabling these devices or ports, you free up IRQs for other more important devices such as your Sound Card.

For Windows 2000/XP please click here for information regarding fixing IRQ sharing conflicts and special optimizations.

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