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    SubjectRe: Changing CPU Speed while running Linux
    On Wed, 13 Jun 2001, Magnus Sandberg wrote:

    > I have a brand new Dell Inspiron 8000, laptop. It can run in 700 MHz or
    > 850 MHz. The manual says that the machine/BIOS switches speed dependent on
    > CPU load. I have not installed Linux yet, but it works with Win2000.

    Intel Speedstep iirc. My Vaio also has it. My findings so far:

    On mains it runs at 700MHz, whilst on batteries it drops to ~550MHz.
    If I boot an ACPI enabled kernel, the speed changes according to CPU
    load, but with a smaller window. I've seen it go as low as 50MHz,
    but only up to a maximum of 200MHz. The fact that it only has a maximum
    of 200MHz in this mode probably explains the need for the no-idle switch
    in the current ACPI implementation.

    As there are no public documents on Speedstep, it's not clear to me
    whether this is a limitation of Speedstep, or the ACPI implementation.
    Judging by the fact that Windows seems to run at full speed, I'd
    be inclined to think the latter.



    | Dave Jones.
    | SuSE Labs

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