[linux-audio-user] audiophile 2496 - spdif in

Robert Jonsson linux-audio-user@music.columbia.edu
Thu Oct 9 07:17:00 2003


Thursday 09 October 2003 12.26 skrev wes schreiner:
> jordan muscott wrote:
> > Ok to be honest I'm not gonna switch distros...... but are you saying
> > that Redhat offers you extra software that allows you to change the
> > IRQs that your pci cards are on?
>
> There is no such software on any distro. Your motherboard's BIOS decides
> which PCI slots get which IRQs. In a few motherboards the BIOS lets one
> select which IRQs get assigned to certain slots, but most don't. So with
> most motherboards all one can do is move cards around to different slots
> and then see what IRQ gets assigned. If your sound card and your
> ethernet card are sharing an IRQ, that's because those PCI slots used
> both have the same IRQ assignment. If you swap just those two cards
> slot-for-slot they will end up with the same IRQ again. Try moving just
> one of the cards to another slot. If all of your slots are full then
> move multiple cards.
>
> On some motherboards with some processors you can turn on Local APIC
> support in your kernel config and get more IRQs to work with. Dual
> processor motherboards, even if they have only one CPU installed, can do
> this to get more IRQs. If you have dual CPUs you should already be
> running a SMP kernel and you probably don't have IRQ assignment
> problems. If you do, it's back to juggling cards.
>
> wes

Hi,

I'm pretty sure I've read that APIC is a no no and should be avoided. 

Here's a link to some interesting info about "normal" IRQs in a PC. There is 
more to it than just having an "OWN" IRQ, they have different priorities.

http://myweb.cableone.net/eviltwin69/Arcana.html#IRQs

See also (the source)
http://www.djcj.org/LAU/guide/Low_latency-Mini-HOWTO.php3


/Robert