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

[Rick Taylor]

On Thu, 09 Oct 2003 07:49:02 -0500
"wes schreiner" <wes at infosink.com> wrote:

>Robert Jonsson wrote:
>
>>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

http://www.ibiblio.org/mdw/HOWTO/Serial-HOWTO-8.html#ss8.1

>>>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. 
>>  
>>
>
>I'd like to see what you read.  In my experience it either works or it 
>doesn't.  One can't avoid using APIC interrupts in a dual-processor 
>system. 
>
>>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
>>
>>  
>>
>
>Yes, that HOWTO has good info, as far as it goes.  One thing I would add 
>though, is that when using non-APIC interrupts the interrupt priority is 
>not fixed in stone (or silicon, as it were).  Using the program 
>"irqtune" one can change interrupt priorities (see 
>http://www.best.com/~cae/irqtune ).  I havn't used irqtune in a while, 
>not since kernel 2.2 days, so I'm not altogether sure that it works 
>correctly with 2.4.x kernels.  On Debian it is in the "hwtools" 
>package.  Hmm, I just tried it on a box with a 2.4.21+lowlatency kernel 
>and it seems that it worked, though it gave some warnings.  I can't 
>really test if the IRQ priorities have changed though.   YMMV.
>
>wes
>
>
>