From: Dave Jones <davej@codemonkey.org.uk>
To: "Grover, Andrew" <andrew.grover@intel.com>
Cc: Valdis.Kletnieks@vt.edu, John Bradford <john@grabjohn.com>,
Seamus <assembly@gofree.indigo.ie>,
linux-kernel@vger.kernel.org
Subject: Re: CPU throttling??
Date: Mon, 3 Feb 2003 21:18:06 +0000 [thread overview]
Message-ID: <20030203211806.GA21312@codemonkey.org.uk> (raw)
In-Reply-To: <F760B14C9561B941B89469F59BA3A84725A14A@orsmsx401.jf.intel.com>
On Mon, Feb 03, 2003 at 01:14:18PM -0800, Grover, Andrew wrote:
> You save the most power when the CPU is at the lowest voltage level, and
> in the deepest CPU sleep state (aka CPU C state).
>
> 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 ?
Dave
[1] Unsure about the crusoe.
--
| Dave Jones. http://www.codemonkey.org.uk
next prev parent reply other threads:[~2003-02-03 21:13 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-03 21:14 CPU throttling?? Grover, Andrew
2003-02-03 21:18 ` Dave Jones [this message]
2003-02-03 21:41 ` John Bradford
2003-02-03 22:14 ` H. Peter Anvin
2003-02-03 22:31 ` Ville Herva
2003-02-04 10:22 ` Seamus
2003-02-04 10:31 ` John Bradford
2003-02-04 11:01 ` Seamus
-- strict thread matches above, loose matches on Subject: below --
2003-02-03 21:51 Grover, Andrew
2003-02-03 15:47 Joeri Belis
2003-02-03 16:55 ` CPU throttling?? Seamus
2003-02-03 17:00 ` Dave Jones
2003-02-03 17:04 ` Martin Hermanowski
2003-02-03 17:13 ` John Bradford
2003-02-03 18:57 ` Valdis.Kletnieks
2003-02-03 19:02 ` Dave Jones
2003-02-03 19:09 ` Martin Hermanowski
2003-02-03 19:20 ` John Bradford
2003-02-04 14:12 ` Erik Mouw
2003-02-03 19:14 ` Matt Reppert
2003-02-03 19:24 ` Valdis.Kletnieks
2003-02-04 14:34 ` Daniel Egger
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