High Pitched Whine

Julian Elischer julian at elischer.org
Tue Jun 6 14:18:08 UTC 2006

Paul Lipps wrote:

> On Jun 6, 2006, at 1:10 AM, Joseph Koshy wrote:
>> The only thing that I can think of that could think of that
>> could whine is a flaky magnetic component.
>> Does the frequency of the whine change if you change HZ?
>> Does the whine reduce if the processor is fully compute
>> bound?
> Yes, the whine actually goes away under a full load. It is  
> intermittent when the CPU is being stressed intermittently, and of  
> course constant when the CPU is idle.
> I am going to try compiling a new kernel with a reduced HZ setting as  
> suggested. Is the output of this command:
> sysctl kern.clockrate
> displaying the current HZ setting? If so it's 1000 at the moment. I  
> will compile a new kernel using the GENERIC configuration file with  
> only the HZ option changed to 100 rather then 1000 and report my  
> findings.
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The whine is probably coming from an element in the power supply.
The hlt systctl that you mention allows the processor to halt when not 
in use
and only wake up when busy or at interrupts (minimum of 'hz' times per 

A halt state uses a lot less power  so the current load
goes up and down with a 1kHz  base and some random variance.
When loaded this can not be heard because the current is more ccontinuous.

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