linux-kernel - Re: [linux-pm] Power Management framework proposal

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Date:	Fri, 27 Jul 2007 12:04:54 +0000
From:	Pavel Machek <pavel@....cz>
To:	Ondrej Zajicek <santiago@...reenet.org>
Cc:	Arjan van de Ven <arjan@...radead.org>, david@...g.hm,
	Igor Stoppa <igor.stoppa@...ia.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] Power Management framework proposal

Hi!

> > let me give you a real world example then, and the numbers I'm using are
> > ballpark the same as you'll find in a (mobile) core 2 duo datasheet, I
> > just rounded them a little so that the math works out nice.
> > 
> > power at full speed: 34W
> > power at half speed: 24W
> > power at idle: 1W
> 
> I have usually seen different numbers, for example:
> 
> http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/30430.pdf

Trust Arjan, modern cpus work as he describes.

> Although this paper speaks about thermal design power instead of power
> consumption, i suppose that it should be roughly equal.
> 
> For example Athlon 64 3700 (ADA3700AEP5AR):
> 
> 2.4 GHz, 1.5 V -> 89 W
> 2.2 GHz, 1.4 V -> 72 W
> 2.0 GHz, 1.3 V -> 53 W
> 1.8 GHz, 1.2 V -> 39 W
> 1.0 GHz, 1.1 V -> 22 W

I guess that means athlon 64 is 'old'.

> Even my measurement on PC (Athlon X2, VIA K8T890) of complete PC power
> consumption shows that it is more efficient to be busy for 2 time units
> on 1 GHz than be busy for 1 time unit and be idle for 1 time unit
> on 2 GHz.
> 
> 1 GHz:
> both cores idle:	48 W
> one core busy:		57 W
> two cores busy:		66 W

2 sec decoding video at both cores: 132J

> 2 GHz:
> both cores idle:	54 W
> one core busy:		78 W
> two cores busy:		95 W

1 sec decode @ 2GHz + 1 sec idle @ 1GHz: 143J

So even on your hw difference is not too big... and take a look at
numbers from core2duo.

Actually...

4 sec decode @ 1 core @ 1GHz: 57*4=228J
1 sec decode @ 2 cores @ 2GHz, then idle: 95 + 48*3 = 142+95 = 235J...

Ok, so it is still 	 win, but even smaller one..
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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