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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.

-hpa


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