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SubjectRe: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.
David P. Reed wrote:
> H. Peter Anvin wrote:
>> Rene Herman wrote:
>>>
>>> I do not know how universal that is, but _reading_ port 0xf0 might in
>>> fact be sensible then? And should even work on a 386/387 pair? (I
>>> have a 386/387 in fact, although I'd need to dig it up).
>>>
>>
>> No. Someone might have used 0xf0 as a readonly port for other uses.
>>
> As support: port 80 on the reporter's (my) HP dv9000z laptop clearly
> responds to reads differently than "unused" ports. In particular, an
> inb takes 1/2 the elapsed time compared to a read to "known" unused port
> 0xed - 792 tsc ticks for port 80 compared to about 1450 tsc ticks for
> port 0xed and other unused ports (tsc at 800 MHz).
>

Any timings for port 0xf0 (write zero), out of curiosity?

-hpa


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