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SubjectRe: rdtsc to mili secs?
H. Peter Anvin wrote:
> Followup to: <>
> By author: Pavel Machek <>
> In newsgroup:
> > >
> > > 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.

What's this "duty cycle throtteling"? Some people seem to think this
refers to changing the duty cycle on the clock, and thereby saving
power. I think it doesn't save any power if you do it that way. You
are referring to the duty cycle on a "stpclk" signal, right?


> 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.

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