On Mon, 10 Mar 2008 11:00:08 +0100
Pavel Machek <pavel@xxxxxx> wrote:
> On Sun 2008-03-09 15:16:59, Pierre Ossman wrote:
> > 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.
>
I figured that was the case. But I did not see any difference in powertop.
> > 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.
I guess the only way to find out is to disassemble the DSDT. Exposing myself to such concentrations of ACPI is not an appealing project. :/
--
-- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org
PulseAudio, core developer http://pulseaudio.org
rdesktop, core developer http://www.rdesktop.org
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