On Sun 2008-03-09 15:16:59, Pierre Ossman wrote: > I'm beginning to think this is a lost cause. I've tried several variants, all without satisfactory results. > > In case anyone else has any more ideas, I'll detail what I've found influences the noise: > > 1. C state > > This is the big one. There is no noise as long as C3 is avoided (processor.max_cstate). > > 2. uhci_hcd driver > > USB is somehow involved in this problem. Unloading the uhci_hcd driver almost entirely kills the noise on a 1000 HZ NO_HZ kernel. On a 100 HZ, no NO_HZ kernel, the effect is very small, but still there. USB keeps processor out of C3 in many cases. > 4. Battery and AC > > The noise increases with the battery present and also when the AC supply is removed. > On battery, some machines swap C3 for "secret" C4, which is slower but saves power. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
