lkml.org 
[lkml]   [2009]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    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
    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/

    \
     
     \ /
      Last update: 2009-01-29 21:51    [W:0.030 / U:29.588 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site