Forcing IRQs to PCI slots under Windows XP

By The Best Alias
Nov 8, 2004
  1. This is more of a discussion than a question:

    I have a particular piece of audio hardware that doesn't work properly unless it has it's own IRQ. I discovered that WinXP pretty much tends to put all the PCI slots, and most everything else on a shared IRQ10. Oh man I was doing cartwheels when the hardware manufacturer suggested I go back to Win98. They said there was a way to force IRQs in XP but they couldn't tell me how to do it because it was a modification to the operating system and they didn't want to be liable. So anyway, here's what I figured out after like 10 tries and it does work.

    During the initial stages of XP setup, there is a prompt to press F5 if you need to install SCSI or Raid drivers. At this point, you press F7. This allows you to change the hardware abstraction layer to that of a standard PC and IRQs can now be assigned in BIOS. There is a cost, you lose all ACPI features. Fortunately for me, all this means is when I shut down, I physically have to switch the machine off. I don't really rely on ACPI for anything. I have notice no other ill effects from this OS mod. Note: If you ever do a dual processor board, you'll need to hit F7 during OS install. Kinda how I figured this out by trial and error.

    I will throw out a question. Does anybody know another way to force IRQs under Windows XP?

    So anyway.... now my sound device and my video card each have their own interrupts and my machine is big dumb and happy. The sound card in question is a Terratec EWS88MT which is an 8 channel multi-track card. Not exactly top of the line, but it does what it's supposed to as long as it isn't sharing an IRQ.
  2. Mictlantecuhtli

    Mictlantecuhtli TS Evangelist Posts: 4,345   +11

    As far as I know, that's the only way. And you can get the machine to turn itself off if you enable APM from BIOS and from XP's power management settings. I don't really know what the point was in the whole ACPI thing, seems to me it just has more problems than benefits.
  3. MMH

    MMH TS Rookie

    Im havin some vid probs, so I tried doin it but it asks for f6 not f5.
  4. Blakhart

    Blakhart TS Rookie Posts: 353

    Acpi is for power savings, what you're looking for is apic. Apic controls the interupts. Acpi runs fine without apic. You need to disable apic in bios, if your bios allows. I suppose sound card problems stem from latency more than lack of a dedicated irq, and disabling apic can indeed reduce latency.
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