Re: AMD's PowerNow?
From: "Alan Shutko" <ats@acm.org>
> Derek Broughton <derek_broughton@hotmail.com> writes:
>
> > As I understand it, speed-step is not supported because it's a typical
> > kludge for Windows. Linux doesn't need it because it idles when not
busy
> > instead of using busy loops.
>
> No, Speedstep is not supported because Intel won't release
> documentation on it (specifically, how to know when it's turned on or
> off so the kernel can adjust timing loops). It _does_ give a power
> benefit when used on my machine.
I have a real problem buying into that explanation. Why would Intel create
Speed-step cpus and then not let you know how to use it? It's no benefit to
Intel unless Microsoft specifically paid them to add the functionality and
keep it exclusive to them. But Microsoft couldn't care less about energy
saving. Seems way too much like a conspiracy theory for me.
As for power benefits on your machine, my understanding is that the kernel
idles when it can but some applications can still keep the cpu busy.
Obviously you'll save power over a limited period of time if you slow down
the machine - but where's the benefit? It makes the application run longer,
and your battery will probably still run out at the same point in your
processing - just after a longer elapsed time.
derek
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