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    SubjectRe: Linux 2.6.29-rc6


    On Mon, 9 Mar 2009, Jesper Krogh wrote:
    >
    > First boot.
    > [ 0.000000] ref_freq: 2311825 pit_freq: 2310386
    > Second boot:
    > [ 0.000000] ref_freq: 2311803 pit_freq: 2310190
    > Third boot:
    > [ 0.000000] ref_freq: 2311824 pit_freq: 2310080
    > Fourth boot:
    > [ 0.000000] ref_freq: 2311831 pit_freq: 2310130

    It's really quite impressively stable, but the fast-PIT calibration
    frequency is reliably about 3/4 of a promille low. Or, put another way,
    the TSC difference over the pit calibration is just a _tad_ too small
    compared to the value we'd expect if that loop of pit_expect_msb() would
    really run at the expected delay of a 1.193182MHz clock divided by 256.

    And it's stable in that it really always seems to be off by a very similar
    amount. It's not moving around very much.

    I also wonder why it seems to happen mainly just to _you_. There's
    absolutely nothing odd in your system, neither a slow CPU or anything
    else that would stand out.

    Grr. Very annoyingly non-obvious.

    Linus


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