Re: Thin high-pitched noise on Inspiron 510m with the ACPI "processor" module

[Stuart Prescott <debian@nanonanonano.net>]

Hi JB,

I can confirm this one with my HP nx7010 (Centrino processor).

it seems to be something to do with the processor going into sleep modes
to save power. There has been significant discussion on kerneltrap,org
about this recently related to the proposals to change the HZ value in
the kernel. The suggestion has been made that it has to do with poor
quality components (capacitors were blamed, IIRC) in the power supplies
that tend to buzz as the power consumption goes up and down.

One thing that I have found is that if I increase the load on the
processor or plug in some USB devices (which presumably does the same
thing) then it goes away...

So if you're feeling like some further experimenting.... does it buzz
under 2.4 kernels? (HZ=100 in 2.4 series). If you feel like recompiling
your kernel, try changing the value for HZ in the headers back to 100
and see what that does for you.

I'd quite like to nail this one down too, but I think we need a number
of people with different machines (and lots of time for recompiling
kernels...) to be able to come up with some definitive empirical
understanding of what's going on. (and it seems that kernel hackers
don't use laptops so they've never noticed this)

cheers
Stuart