Subject: Re: [linux-audio-user] APIC is bad?
From: Jan Depner (eviltwin69_AT_cableone.net)
Date: Sat Jul 17 2004 - 15:26:34 EEST
On Sat, 2004-07-17 at 06:33, Malcolm Baldridge wrote:
> > 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.
>
It may take a few tries to get everything where you want it though.
> 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.
>
In addition to the time to determine interrupt source there is another
problem with shared interrupts - don't use any USB devices or run your
network while trying to record.
Jan
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