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SubjectRE: CPU throttling??
Date
> From: Dave Jones [mailto:davej@codemonkey.org.uk] 
> > Throttling offers a linear power/perf tradeoff if your
> system doesn't
> > have C state support (or if you aren't using it) but really it is
> > preferable to keep the CPU at its nominal speed, get the work done
> > sooner, and start sleeping right away. The quote above
> makes it sound
> > like the voltage is scaled when throttling, and that isn't
> accurate -
> > voltage is scaled when sleeping (to counteract leakage current), at
> > least on modern Intel mobile processors.
>
> Most (all?[1]) other modern x86 mobile processors behave the
> way I mentioned.
> AMD Powernow (K6 and K7), VIA longhaul/powersaver all have
> optimal voltages
> they can be run at when clocked to different speeds. By way
> of example, a table from
> my mobile athlon..
>
> FID: 0x12 (4.0x [532MHz]) VID: 0x13 (1.200V)
> FID: 0x4 (5.0x [665MHz]) VID: 0x13 (1.200V)
> FID: 0x6 (6.0x [798MHz]) VID: 0x13 (1.200V)
> FID: 0xa (8.0x [1064MHz]) VID: 0xd (1.350V)
> FID: 0xf (10.5x [1396MHz]) VID: 0x9 (1.550V)
>
> Sure I *could* run that at 523MHz and still pump 1.550V into it,
> but why would I want to do that ?

Voltage scaling. Yes, it's widespread. I was referring to an additional
capability to lower voltage while the CPU is sleeping. But I digress.

But this whole thread didn't start as a discussion of voltage scaling,
it started as a discussion of throttling - e.g. keeping your system at
1400MHz 1.550V and simulating a slower processor by toggling the STPCLK#
pin. And you're exactly right that no you *wouldn't* want to do that.

I think we are in agreement. ;-)

Regards -- Andy
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