Messages in this thread | | | Date | Thu, 29 Jan 2009 14:47:05 -0600 | From | Wes Felter <> | Subject | Re: a question about p4_clockmod module on Xeon quad core processors |
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This will give you an effective speed of 250 MHz:
for cpu in 0 1 2 3; do cpufreq-set -c $cpu -g userspace cpufreq-set -c $cpu -u 2.0GHz wrmsr -p $cpu 0x19A 0x12 done
0x19A is the IA32_CLOCK_MODULATION MSR and 0x12 is calculated from the Intel 64 and IA-32 Architectures Software Developer’s Manual section 13.5.3. Legal MSR values are 0x12 (12.5% duty cycle) - 0x1E (87.5%) or 0x00 for 100%. I tested it on a quad-core Xeon and it works.
This is somewhat reckless, so use it with caution.
Wes Felter - wesley@felter.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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