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Subject: Re: CPU throttling??
From: Daniel Egger <degger@fhm.edu>
To: Valdis.Kletnieks@vt.edu
Cc: Matt Reppert <arashi@arashi.yi.org>, linux-kernel@vger.kernel.org
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Am Mon, 2003-02-03 um 20.24 schrieb Valdis.Kletnieks@vt.edu:

> I knew that.  The question I asked was whether halted at 700Mhz takes mor=
e
> power than halted at 400Mhz...=20

PowerPC CPUs will shut down unneeded units. There's no such things as a
"hlt" instruction. The natural way to slow down the CPU causing more
sparetime to shut down single units is to throttle the dispatching of
instructions for which there's are flags in the control register set.

I've no idea where the frequency scaling should happen but it either
needs some hardware clock control or it's the mentioned dispatch
throttling. In case of the former there'd be some powersave effects
because the power drawn by a CPU is direct proportional to the
frequency. In the latter case the difference between an automatically=20
sleeping 700Mhz and a throttled 700Mhz cpu at "400Mhz" should be pretty
small, in case the cpu is mostly idle.

--=20
Servus,
       Daniel

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