Non-ACPI and IRQ changes

[Stephen Fleece]

Is there any way to change IRQ assignments on a "Standard
PC" (non-ACPI) XP system using device manager? In device
manager, the devices I want to change all have "use
automatic settings" checked and greyed out, so I can't
change it. I have disabled IRQ steering and rebooted.

I'm have image quality problems with a PVR card
(Hauppauge Win-PVR 350) that does MPEG encoding and
decoding. An expert on a PVR card told me to change the
IRQ so that it is not shared with my display adapter
since the PVR card uses overlay video functions.

 

[Paul]

It is not an ACPI verses Standard PC issue as far as IRQ assignment goes. My
ACPI system won't allow me to change any IRQ resources for my TV card either.

As far as IRQ assignments of PCI devices go, the architecture was designed so
that devices could share IRQ's. The original design only allow for 4 IRQ's to be
"grabbed" from the pool of 16 available IRQ's so if your board came with 6 PCI
expansion slots, then at 3 cards would have the same IRQ's. As the motherboards
started to add more and more controllers onboard which were PCI based, then
there became fewer and fewer slots which did NOT share IRQ's. My motherboard
has 5 PCI and 1 AGP slot but only has one slot which does not share an IRQ.

If your ultimate desire is to isolate the TV card from any other device so the
IRQ's are not shared, you will need to move the card to a different slot (you
might check the motherboards documentation to see if they list a chart of IRQ
assignments, this might speed up the process).

BOL

Paul