Messages in this thread | | | Date | Wed, 28 Jan 2009 21:45:39 -0500 | From | Dave Jones <> | Subject | Re: a question about p4_clockmod module on Xeon quad core processors |
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[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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