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List:       linux-kernel
Subject:    Re: SMP cpu deep sleep
From:       Benjamin Herrenschmidt <benh () kernel ! crashing ! org>
Date:       2004-08-21 0:53:45
Message-ID: 1093049624.9932.262.camel () gaston
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On Sat, 2004-08-21 at 02:44, Wes Felter wrote:

> The CPU hotplug patch is the way to go, but the hardware is the problem. I
> talked to an Intel CPU architect at MICRO last year and he confirmed that
> SMP Intel systems don't support any low-power modes besides HLT. AMD's
> documentation says that Opterons support voltage/frequency scaling (aka
> Cool 'n' Quiet), but AFAICT the documentation is wrong. In summary, you
> are doomed.

Well, with intel CPUs maybe ;) On PPC we can put some CPUs (at least the
desktop ones and the 970, I don't know about POWER3/4/5) into SLEEP mode
after flushing all caches & masking all IRQs to them, and get them out
via an IPI, or we can mask EE as well and get them out via a soft reset
if we have access to it.

Ben.


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