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SubjectRe: a question about p4_clockmod module on Xeon quad core processors
[please don't top-post]

On Wed, Jan 28, 2009 at 06:06:37PM -0800, Xiaoning Ding wrote:

> > > I have tried the p4-clockmod module in Linux kernel
> > 2.6.29 on Xeon 5355 quad-core CPUs with no luck. It seems
> > current p4-clockmod driver still cannot support Intel Quad
> > core processors, right?
> > >
> > > I know I can also use acpi-cpufreq. It can only scale
> > down the frequence from 2.67GHz to 2GHz. But I need some
> > lower frequencies for some experiments.
> >
> > p4-clockmod doesn't change the processor frequency.
> > Because of common misconceptions like this, the user
> > interface has been removed.
> >
> > In 2.6.29, the clock modulation code is called directly
> > from ACPI
> > whenever thermal events indicate that throttling is
> > necessary.
> >
> Thanks for the correction.
> My experiments need to reduce CPU speed. However, I can only reduce the speed by about 30% (from 2.67GHz to 2GHz) with ACPI. That is not enough for the experiments.

The ACPI P-states are nearly always correct, so you won't be
able to go below 2GHz on this system.

> p4-clockmod has not been removed from 2.6.29. It is under the same directory as acpi-cpufreq (arch/x86/kernel/cpu/cpufreq). So I thought it was an alternative approach. But I could not get it loaded.

The driver is present, the _user interface_ has been removed.

Dave

--
http://www.codemonkey.org.uk


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