Subject: [linux-audio-dev] P4 kernel patch/option against denormals
From: derek holzer (derek_AT_x-i.net)
Date: Sun Sep 19 2004 - 16:07:56 EEST
Hi all,
I have had non-stop CPU spikes and freezes related to denormal numbers
on my Pentium 4 1.6GHz laptop ever since I switch to Linux, going from
kernel 2.4.18 up to 2.6.4.
The main applications which seem to be affected are Freqtweak, Jamin and
Pure Data, along with a handful of LADSPA plugins, which can sometimes
make my Ardour sessions a real PITA. Does everyone develop on Celerons
or AMDs these days?!? ;-)
I have pursued the problem in particular with Pure Data, but have been
assured that there is already denormal handling in the program... It has
gotten to the point where either I find a kernel-level solution for the
problem or I buy a new laptop!
Tim Blechman reported on the PD list that his denormal problems only
started when he switched from SuSE to Gentoo. My suspicion is that the
SuSE kernel developers either cooked up a very good patch against
denormals, or they are using a proprietary Intel compiler for their
kernels which somehow alleviates the problem. For my own purposes, the
former is more attractive than the latter, of course.
Tim also mentioned that some P4s have a Denormals-As-Zero switch to
handle the problem [although I suspect that my CPU might be too old for
this feature...]. Can anyone explain how such a DAZ switch can be tested
for and toggled?
Can anybody shed some light on the situation? I would hate to have to
ditch a decent computer over this issue.
best wishes,
Derek
-- derek holzer ::: http://www.umatic.nl ---Oblique Strategy # 127: "Openly resist change"
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