Evil Home Stereo

Since I upgraded my workstation and my notebook to a 2.6 kernel, both emitted an annoying hissing sound from the speakers. Judging from the posting on several mailinglists and forums am I not the only one who hears this. But nobody has a clue what it could be. Except the guys on the LKML of course.

A Google query I hadn’t tried yet (because I didn’t notice until now that it’s depending on the CPU load) led me to this posting by Aaron Burt which explains my problem perfectly. And the solution posted by Prakash K. Cheemplavam does the trick.

The sound goes away if you disable the Athlon Powersave mode via athcool. Doh. That’s bad. Ok, it’s really a relieve for my ears but I need that Powersave mode.

Prakash mentions that this is a known problem for the VIA KT133 chipset under Windows (my machines are one KT133 and a KT266). And athcool even offers an “fixup” mode which should fix some “VIA audio problems”. Which doesn’t help.

As I neither want to do without the Powersave mode nor can stand that sound, I’ve got to find another solution. One question is why it didn’t happen with a 2.4 kernel. Maybe Frank v. Waveren points into the right direction and the to 1000 Hz increased timer interrupt is the culprit. When I find the time I’ve got to check if the variable interrupt patch posted by Jean-Marc Valin or the ones by the High Resolution Timers project helps.