Re: [Alsa-user] Change IRQ on the soundcard

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On Friday 03 December 2004 18:57, Lee Revell wrote:
> On Fri, 2004-12-03 at 11:48 +0100, Michael Gerdau wrote:
> > > >I have an Abit SA7 motherboard with an onboard SIS7012 (C-Media 9738)
> > > >sound card. I have a Terratec Aureon 7.1 Space that is of course much
> > > >better, and I would like it to _not_ share IRQ with my S-ATA
> > > > controller and TV-card.
> > >
> > > I'm always tempted to ask "why? what problems are you seeing?"  If the
> > > hardware is happy to share interrupts, why aren't you?
> >
> > I'm always surprised to learn that many folks don't seem to know
> > the very simple reason (at least for audio):
> > Not sharing IRQs among devices does reduce latency (and thus also
> > reduces the risk of dropouts).

> Anyway if you are sharing an interrupt with a disk or network adapter
> the best way to fix it is to just try another PCI slot.  Your
> motherboard manual will often tell you which PCI slot is shared with
> which onboard device.  Try the slot that is shared with USB.

I have been following this with much interest. My system actually does have=
=20
the problem of slowing down heavily because a network adapter and sound car=
d=20
share the same IRQ 5, managed by acpi(?). I need acpi because otherwise I=20
wouldn't have sound at all because of IRQ problems. And I can't change any=
=20
pci slot because thi is a small notebook. Built in hardware.

guido@jvc:~> cat /proc/interrupts
           CPU0
  0:     858521          XT-PIC  timer
  1:       4085          XT-PIC  keyboard
  2:          0          XT-PIC  cascade
  3:        246          XT-PIC  ehci-hcd
  4:          0          XT-PIC  usb-uhci
  5:      62786          XT-PIC  eth0, usb-uhci, Ricoh Co Ltd RL5c475, Inte=
l=20
82801DB-ICH4
  7:          1          XT-PIC  ohci1394, usb-uhci
  8:          2          XT-PIC  rtc
  9:      54497          XT-PIC  acpi
 12:         15          XT-PIC  PS/2 Mouse
 14:      45226          XT-PIC  ide0
NMI:          0
LOC:          0
ERR:          0
MIS:          0

So what can I do? The idea of allowing acpi or alsa to manually set IRQs is=
=20
compelling. Another idea would be to let acpi check system speed for each=20
present IRQ setting from which it can deduce what IRQ settings would be bes=
t.=20
After a while (i.e. a couple of reboots) acpi would learn that with a certa=
in=20
setting there would be only very few system slow downs.

Anyway. Can't wait till this utopia is turned into reality. Recently there =
had=20
been an exchange about howto manually set IRQs on a german mailing list.=20
Someone came up with a few links which I haven't read through yet or even=20
tried. If you speak some german you might want to know about them:

<quote>
> in meinem Rechner sieht es mit den IRQ's recht eng aus.
>
> Wie kann ich z.B. f=FCr den Firewireport einen anderen IRQ
> festlegen?
Das habe ich auch schoneinmal gefragt und von David super Antworten=20
bekommen. Ich denke, das d=FCrfte deine Fragen auch beantworten.=20
=A0
http://lists.suse.com/archive/suse-linux/2004-Aug/3428.html
und hier gehts weiter:=20
http://lists.suse.com/archive/suse-linux/2004-Sep/0008.html
</quote>

Guido