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    SubjectRe: CPU throttling??
    On Mon, Feb 03, 2003 at 01:14:18PM -0800, Grover, Andrew wrote:

    > You save the most power when the CPU is at the lowest voltage level, and
    > in the deepest CPU sleep state (aka CPU C state).
    > Throttling offers a linear power/perf tradeoff if your system doesn't
    > have C state support (or if you aren't using it) but really it is
    > preferable to keep the CPU at its nominal speed, get the work done
    > sooner, and start sleeping right away. The quote above makes it sound
    > like the voltage is scaled when throttling, and that isn't accurate -
    > voltage is scaled when sleeping (to counteract leakage current), at
    > least on modern Intel mobile processors.

    Most (all?[1]) other modern x86 mobile processors behave the way I mentioned.
    AMD Powernow (K6 and K7), VIA longhaul/powersaver all have optimal voltages
    they can be run at when clocked to different speeds. By way of example, a table from
    my mobile athlon..

    FID: 0x12 (4.0x [532MHz]) VID: 0x13 (1.200V)
    FID: 0x4 (5.0x [665MHz]) VID: 0x13 (1.200V)
    FID: 0x6 (6.0x [798MHz]) VID: 0x13 (1.200V)
    FID: 0xa (8.0x [1064MHz]) VID: 0xd (1.350V)
    FID: 0xf (10.5x [1396MHz]) VID: 0x9 (1.550V)

    Sure I *could* run that at 523MHz and still pump 1.550V into it,
    but why would I want to do that ?


    [1] Unsure about the crusoe.

    | Dave Jones.
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