Fixing That IRQ Conflict

By groovewerx
Mar 25, 2002
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  1. From time to time, particularly when reinstalling Windows, we all get the occasional (or not so occasional) IRQ problem. Windows is notorious for not allowing you to directly change which IRQ's are assigned to which device so we must use a rather convoluted method to change the IRQ which involves uninstalling devices and reserving IRQ's. Seasoned veterans often reserve an IRQ for a particular device before installing anything, this is the best method but sometimes, a reinstall is not preferable to your time constraints or indeed your sanity so here's a pretty fail-safe method of changing a devices IRQ assignment: (these instructions are for Windows 98/ME).

    Please also note that windows 2000/XP may well put a large number of devices on IRQ 11. This is a virtual IRQ which means that they are all sharing IRQ 11. It shouldn't be a problem but if it is, this method should still work...

    Make sure you have the device drivers for all your devices to hand

    1. The first job is to uninstall all but one of the devices which are conflicting from windows from Device Manager ('Start'>'Settings'>'Control Panel'>'System' then click on 'Device Manager tab') double-click on a device then click on it's properties tab and choose 'Disable this device (do not use)').

    2. Now you need to reserve an IRQ for the device you left installed so that when Windows is restarted and reinstalls the other device(s) it cannot use the IRQ you have reserved which will leave it free for your intended device. You can reserve an IRQ from Device Manager by double-clicking on the 'Computer' icon and choosing 'Reserve Resources' then clicking on the IRQ radio button. You will now be able to choose an IRQ number to reserve - it may be wise to reserve the original IRQ that the device was on as it is likely to function correctly on that IRQ.

    3. Now you need to simply restart your system and supply the necessary drivers Windows asks for and it should automatically redefine the IRQ's such that the device you did not uninstall has a unique (i.e. it's own) IRQ.



    This method is perfectly valid too for just assigning a unique IRQ to a device in your system if it requires one or you would prefer it to have one. Please note however that some IRQ numbers are pre-reserved for particular devices - usually:

    0 - System timer

    1 - Keyboard

    3 - COM port 2 (serial)

    4 - COM port 1 (serial)

    6 - Floppy drive controller

    8 - System CMOS (BIOS) clock

    12 - Mouse

    13 - Numeric data processor

    14 - IDE controller channel 1

    15 - IDE controller channel 2

    This may seem like a lot of IRQ's to be unavailable but infact most of them can be shared quite happily by 2 or more devices. Please also note that Souncards usually work best on or may even require IRQ 5.
  2. uncleel

    uncleel Newcomer, in training Posts: 1,145

    :wave:Welcome & Hello:wave:
    Excellent post ! This is good info to add to the archive of 3DS information.
    previous info:
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