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assigning irq's in bios

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by mithrandir

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You cannot manually assign irq resources to pci cards in windows. I have learned that you can set plug and play os to disabled in the bios and attempt to assign irq recorces to different pci bus slots in the bios. I have found this to be difficultat best, the goal being a seperate irq for each pci device. Sometimes it seems the only solution is to switch cards and slots manually to achieve the desired results. Some slots seem to share irq resources no matter what. I would like to have some basic guidelines given that bios are different on different motherboards.

3 replies

by d_v ant

You are right when you say that some slots share IRQ resources. There is no way around this with those boards. It is nearly impossible to find a board that does not have shared slots. I don't know of any personally, but I haven't looked either. Nowadays, with IRQ Steering, sharing IRQs isn't as much of a problem as it used to be. The PC can normally keep things running smooth even with a few devices sharing IRQs. I simply try to keep my Video card and Network card on seperate IRQs as their performance can degrade when they are shared. Other than that, I let the BIOS make the decisions about everything else.

by mithrandir

Unacceptable is too strong, I appreciated the answer. But I am specifically looking for guidance in assigning the irqs from system setup, it is confusing to me. The problems arise for my gamer customers, usually between the video and sound card.

by thechas

The BIOS assigned IRQs only work for DOS style operating systems.

Any Plug-and-Play OS will assign IRQs as it deams proper for the hardware and software configuration.

In fact, XP assigns almost all plug-in cards to a single IRQ!!!

There isno "supported" way to change IRQ assigments in XP.

For W98 and W95, you can disable IRQ steering, and force Windows to re-evaluate the shared IRQs.

Check out this link for more details on how Windows assigns IRQs.
http://members.bellatlantic.net/~mrscary/devenum.htm

Remove any spaces from the pasted link.

Here is a Microsoft article.

http://support.microsoft.com/support/kb/articles/q182/6/04.asp

There is another on disabling IRQ steering, but I misplaced the link.

Chas

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