[lkml]   [2005]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: speedstep-centrino on dothan
    On Wed, 06 Jul 2005 15:58:53 -0400
    Bill Davidsen <> wrote:

    > wrote:


    > > Moreover, I checked on Pentium M 725 and Pentium M 715 that the lowest
    > > frequency at which the CPU can be set safely is not the 600MHz given in
    > > datasheets, but 400MHz instead, with VID#A, VID#B, VID#C and VID#D (see
    > > datasheet for more details) set to 0.908V.
    > >
    > > I can provide a patch, let me know.
    > Slower is better


    Here's a quick trick for getting CPU to lower frequencies than the ones
    read from ACPI tables, while still keeping them available.

    Just add these lines in centrino_cpu_init_acpi(), in speedstep-centrino.c,
    just after (and outside) the first 'for' cycle like this:
    for (i=0; i<p.state_count; i++) { ...

    centrino_model[cpu]->op_points[p.state_count - 1].index = 0x040D;
    centrino_model[cpu]->op_points[p.state_count - 1].frequency = 400000;
    p.states[p.state_count - 1].core_frequency = 400;

    This will enable 400MHz at 908mV, which I found to be useful on Dothan
    CPUs. If you want to get values for other frequencies/voltages, just use
    something like:

    #include <stdio.h>

    int main() {
    unsigned int index, frequency, voltage

    index = (((frequency)/100) << 8) | ((voltage - 700) / 16);
    printf ("%u\n", index);

    frequency is expressed in MHz, voltage in mV, index is the value for
    centrino_model[cpu]->op_points[y].index <- remember to change this y if you
    want to add multiple frequencies besides the ACPI ones; for example, if you
    want 500MHz at 940mV, you could add:

    centrino_model[cpu]->op_points[p.state_count - 2].index = 0x1295;
    centrino_model[cpu]->op_points[p.state_count - 2].index = 500000;
    p.states[p.state_count - 2].core_frequency = 500;

    Sorry if I have been off-topic.


    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2005-07-08 00:05    [W:0.021 / U:47.824 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site