Re: [PATCH 2.6.18 1/1] ACPI: limit cstate on noisy thinkpad t43/p models

[Timo Hoenig <thoenig@nouse.net>]

Hi,

On Mon, 2006-09-25 at 03:06 -0400, Len Brown wrote:

> On Sunday 24 September 2006 07:38, Timo Hoenig wrote:
> 
> > I think it is a more general problem.  The systems with Intel Core Duo I
> > got my hands on all show the symptom:  Once the system is idle, the
> > second core begins to whine.  It's annoying in quiet environments.
> > 
> >       * Turning off the second core makes the whining stop.
> >       * Booting with processor.max_cstate=2 does also make the whining
> >         go away; but it's a bad idea on laptops if once wants to gain a
> >         long run on batteries.
> > 
> > Tested with HZ=250; I'll check whether HZ=100/1000 helps.
> 
> Curious, I have not noticed this on the Core Duo systems I have.
> 
> In the past this has been traced to the voltage switching on the motherboard
> causing the capacitors to vibrate and the motherboard to resonate.
> That is why changing HZ will likely have an effect on the problem.

Yes, that's what I have found to be the culprit, too.  Sorry that I do
not have yet been able to check with different HZ than 250 so far.

> Exactly what model system do you have that is making noise?

* Lenovo ThinkPad T60, several different models
* Fujitsu Siemens e8110

Also, I just got my hands on a Lenovo ThinkPad X60 and ran the same test
[1] as on the other machines but did not hear any noise.

   Timo

[1] Test with Linux 2.6.18-rc6 (with pwd /sys/devices/system/cpu/cpu1)
    while (true); do echo 0 > online; sleep 1; echo 1 > online; sleep 1; done;