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    SubjectRe: a question about p4_clockmod module on Xeon quad core processors
    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

    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 -
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      Last update: 2009-01-29 21:51    [W:0.023 / U:4.992 seconds]
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