Subject: Re: [linux-audio-user] Latency issues with laptops
From: Lee Revell (rlrevell_AT_joe-job.com)
Date: Tue Oct 12 2004 - 04:06:23 EEST
On Mon, 2004-10-11 at 20:51, Mark Knecht wrote:
> On Mon, 11 Oct 2004 21:02:03 -0400, Peter Lutek <plutek_AT_infinity.net> wrote:
> > On Mon, 2004-10-11 at 19:01, Lee Revell wrote:
> > --snip--
> > > But we can at least identify the problematic laptops,
> > > complain to the manufacturers, and warn people not to buy them.
> >
> > has anyone yet compiled such a list?
> >
> I suppose my laptop (also a Compaq - an R3070us) could be considered a
> 'problematic' laptop also, but my thought is that I don't really care
> about ACPI when I'm doing audio anyway. I'm not running on batteries
> or doing any of that sort of stuff when I'm recording and mixing. I
> want ACPI and every other distraction to the machine turned off. For
> instance, I'm seeing far fewer xruns still with fluxbox. I see one or
> two under Gnome. I see bunches of them under KDE. So, at least with
> ACPI off, I think it's not so certain that ACPI is the *only* problem
> here.
>
The LKML poster's main point was that if your laptop implements ACPI
with SMM you WILL get xruns because SMM disables interrupts. Even
disabling ACPI in the kernel will not eliminate the problem 100% because
the hardware sensors will cause the machine to go to SMM mode to enable
the fan for example.
So this _is_ definitely a problem IF your laptop uses SMM to implement
ACPI. It remains to be seen how widespread the issue is, and whether
there is a way to tell whether a given machine has the problem other
than trial and error.
Lee
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