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From
SubjectRe: rdtsc to mili secs?
Date
Followup to:  <20001110154254.A33@bug.ucw.cz>
By author: Pavel Machek <pavel@suse.cz>
In newsgroup: linux.dev.kernel
> >
> > Sensibly configured power saving/speed throttle systems do not change the
> > frequency at all. The duty cycle is changed and this controls the cpu
> > performance but the tsc is constant
>
> Do you have an example of notebook that does powersaving like that?
> I have 2 examples of notebooks with changing TSC speed...
>

Intel PIIX-based systems will do duty-cycle throttling, for example.
However, there are definitely notebooks that will mess with the
frequency. At Transmeta, we went through some considerable pain to
make sure RDTSC would count walltime even across Longrun transitions.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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