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SubjectRe: [RFT] Port 0x80 I/O speed
El Wed, 12 Dec 2007 00:31:18 +0100
Rene Herman <rene.herman@gmail.com> 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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