[Mactel-linux-devel] ACPI on MacBook Pro - high pitched noise

[Miguel F. <mig...@gm...>]

Hi,

On 3/26/06, Matthew Garrett <mj...@sr...> wrote:
>
> On Sun, Mar 26, 2006 at 01:10:14AM -0500, Jimmy Kaplowitz wrote:
> > can see battery output. However, whether or not I have that module
> > loaded, there is an annoying medium-high-pitched tone that continuously
> > comes from my machine when it's in Linux and I have the power cable
> > disconnected. It stops about a second after I plug in the power cable.
> > What might be wrong here? It's very irritating.
>
> Poor quality capacitors resonating when the CPU rapidly switches in and
> out of C2 and C3 powersaving states. Try poking different values into
> /sys/module/processor/parameters/max_cstate - you'll lose battery life,
> but the noise will stop. Alternatively, hacking your kernel to have a HZ
> value of 100 rather than 1000 should improve things.



More information about "high pitched" noises, that seem related to this
problem..
This URL (http://www.thinkwiki.org/wiki/Problem_with_high_pitch_noises)
contain more precise information about the problem
and ways to solve it.

Best regards,


--
Miguel Sousa Filipe