[linux-audio-user] latency questions

D R Holsbeck drh at niptron.com
Tue Oct 15 22:30:01 EDT 2002

On Tue, 2002-10-15 at 17:48, G. M. Bodnar wrote:
> I was running through the low-latency howto and I ran into a couple
> things that seem to be hindering process.
> First off, I'll mention that I'm using a Dell Inspiron 2650 laptop.
> I'm running debian unstable with 2.4.19.

I a,m running the same setup on an IBM A31 Thinkpad, and do not have
problems with latencies. Even while running 24chs in Ardour, using a an
RME H-DSP interface. So I would venture that your problem has more to do
with Dell than Linux.
> 1) DMA transer won't enable.  I've enabled DMA transfers in the kernel
> as suggested by the howto.  However, I'm unable to turn on dma access
> with hdparm.  I'm told the operation is not permitted.

More evidence that it is a hardware issue. Or hardeware/software
incompatibiliy to be more politicly correct.

> 2) IRQ mess.  dmesg lists that almost every device that is detected is
> on irq 10, including the onboard sound (i8x0) and video card (nVidia).
> As a result, in X, I get static and pops as the audio is delayed.
> Searching further, I noticed a message saying the APIC wasn't being used
> due to a buggy bios provided by Dell.  This could explain why everything
> is pushed to IRQ 10.

All my devices end up on 11, but APIC takes care of things nicely.

> Has anyone had these problems, and more importantly, gotten around them?
> I'm not sure if the bios problem mentioned is accurate for the 2650.
> Looking through the kernel source, it clumps a bunch of models together.
> I'm tempted to hack through that and see if it does crash...
> Thanks
> Greg
> --- -
drh at niptron.com

Great spirits have always encountered violent opposition from mediocre
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