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    SubjectRe: [RFT] Port 0x80 I/O speed
    El Wed, 12 Dec 2007 00:31:18 +0100
    Rene Herman <> escribió:

    > Good day.
    > Would some people on x86 (both 32 and 64) be kind enough to compile and run
    > the attached program? This is about testing how long I/O port access to port
    > 0x80 takes. It measures in CPU cycles so CPU speed is crucial in reporting.
    > Posted a previous incarnation of this before, buried in the outb 0x80 thread
    > which had a serialising problem. This one should as far as I can see measure
    > the right thing though. Please yell if you disagree...
    > For me, on a Duron 1300 (AMD756 chipset) I have a constant:
    > rene@7ixe4:~/src/port80$ su -c ./port80
    > cycles: out 2400, in 2400
    > and on a PII 400 (Intel 440BX chipset) a constant:
    > rene@6bap:~/src/port80$ su -c ./port80
    > cycles: out 553, in 251
    > Results are (mostly) independent of compiler optimisation, but testing with
    > an -O2 compile should be most useful. Thanks!
    > Rene.

    On my AMD 3800 X2 (2000MHz) ULi M1697 2.6.24-rc5 i get:

    cycles: out 1844674407370808, in 1844674407369087

    It is not constant but variations are not significant afaics

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