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    SubjectRe: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.
    David P. Reed wrote:
    > Just a thought for a way to fix the "very early" timing needed to set up
    > udelay to work in a way that works on all machines. Perhaps we haven't
    > exploited the BIOS enough: The PC BIOS since the PC AT (286) has
    > always had a standard "countdown timer" way to delay for n microseconds,
    > which as far as I know still works. This can be used to measure the
    > speed of a delay loop, without using ANY in/out instructions directly
    > (the ones in the BIOS are presumably correctly delayed...).

    If we enter from the 32-bit entrypoint, we already don't have access to
    the BIOS, though.


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      Last update: 2007-12-15 06:49    [W:0.021 / U:12.284 seconds]
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