[plug] agp/pci interrupt problems

[Simon Scott (SSC)]

Just for interest:

I found a site that explains a little more than the motherboard manual.
Basically PCI devices *should* be able to share interrupts, altho obviously
some cheaper or less well designed cards have a little problem. The spec
doesnt recommend it, it insists upon it.

AGP cards are notoriously bad at sharing interrupts, which has nothing to do
with the AGP spec but rather the manufacturers.

In particular you should never share an IRQ between a Soundblaster Live and
anything else, and also alot of NICs dont like it much.

Basically I have to disable any devices Im not using if possible (eg USB,
COM ports) to free up interrupts. Each PCI (and AGP) port is connected to
one of four 'Int Pins' which can have an IRQ assigned to them. Obviously you
have to shift devices around so the more sensitive ones are on their own
pin. For example, it appears that on my board it works as follows:

Int Pin #1 - AGP Slot and PCI Slot 1 (closest to AGP)
Int Pin #2 - PCI Slot 2, PCI Slot 3 and ACPI (what the hell is ACPI?)
Int Pin #3 - PCI Slot 5 (and if you have the version of the K7T with onboard
RAID it uses this)
Int Pin #4 - PCI Slot 4, PCI Slot 6 and USB.

So if a disable USB and ACPI (and maybe COM ports) in the bios, and shuffle
a few cards around, I should get each device to have its own IRQ, which
negates the need to track down my sensitive card that causes the crash.

They also recommend disabling 'PCI Delay Transitions' in the BIOS.

This doesnt really solve my 'AGP card doesnt have an IRQ' problem, but I was
interested to see that on a motherboard review site the guy had taken a
screen dump of the IRQs in Windows and no graphics card appeared either.

Can someone on a AGP machine do a quick cat /proc/interrupts or have a look
in the control panel and let me know if this is a common thing?

Thanks fellas

	

-----------------------------------------
Simon Scott
Developer
FlexiPlan Australia Ltd
Level 16/216 St Georges Terrace
Perth Western Australia 6000
Work : (08) 9215 5574
Mobile : 0409 113 359
E-mail: simon.scott at flexiplan.com
-----------------------------------------


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