[linux-audio-user] APIC is bad?

[Malcolm Baldridge]

> Slight side issue, while you guys are on the subject.
> 
> I have my soundcard (an onboard i8x0) sharing an interrupt (IRQ 11) with
> eth0 and usb-uhci. Would this be likely to give rise to xruns in a 
> similar way? 

I think motherboard audio bugs/latency issues will be more of a problem than
shared IRQs.  Turning off the PnP Setting in the BIOS and then "Reset
Configuration Data" may cause a re-assignment to occur during the next time
you go through BIOS POST.

> or is it just a question of physically moving the ethernet card? 

Moving the ethernet card should get you another IRQ, though keep in mind,
it's a bit stranger with PCI than ISA.  To make it even spicier, some PCI
slots are not capable of bus-mastering DMA.  But the answer to your question
is yes: moving the card will get you a different IRQ.

As for the onboard-USB, well, that might be harder to "move".  The problem
is that the IRQs are "mapped" to PCI INT-levels, and it seems that many
system hardware designers get very lazy and slopping with how they use them.

Shared IRQs have been with us for a few years now, and I doubt it's the
source of most xruns people see on their systems these days.  We are talking
about microseconds of additional time to determine the interrupt source
here.  If your xruns are in the hundreds of milliseconds, this is not your
problem.  If you're on the borderlines, THEN it might be something worth
looking into.

This brings up a point about technical diagnostics and troubleshooting: try
to assess the magnitude of your xruns to give you valuable hints as to where
to look for what might be wrong.  If they're in the hundreds of
milliseconds, your problem is most likely a
big-kernel-lock/preemptible-kernel related fault, or just really bad
hardware.  File system choices affect this as well.

Good luck,

=MB=

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