Re: freq. scaling vs power consumption

[michalwd1979]

Hello,
Finally I get all measurements done:
server PE 2850, 2x 3GHz XEON, 3xHDD, water cooling, 1 PSU, with P4-clockmod driver:

IDLE at 375MHz - 199-207W
IDLE at 3GHz - 203-209W (no difference)
F.Load at 375MHz - 210W (you were close Kuba!)
F.Load at 3GHz - 255W-262W

So P4-clockmod can save a few watts with loaded server, however I am not sure if it will save energy (the same task will take much longer to complete). As I thought before it is rather useless for me but maybe someone will benefit from it in specific situation. 
Does anyone has experience with other ways of freq. scaling then P4-clockmod? I assume that "power efficient" servers should have some better way of doing this, but I never used such machine.

Regrads,
Michael W.

Dnia 27 listopada 2007 15:15 Kuba Ober <kuba at mareimbrium.org> napisał(a):

> On Tuesday 20 November 2007, michalwd1979 wrote:
> > I did not make test with fully loaded procs and 375MHz (I forgot) but this
> > situation is rather unusual. With load I want full speed I hoped to save a
> > few wats with no loaded server. Anyway: Server not loaded 3000MHz - 207W
> >  Server not loaded 375MHz - 207W
> >  Server fully loaded (compilation) 3000MHz - 262W
> 
> An unloaded CPU already conserves its power and reducing the clock speed may 
> well not change a thing, which is what you saw.
> 
> You *will* see a big difference in full load power between 3000 and 375 MHz. I 
> expect your full load 375MHz power consumption to be around 217W. Let's see 
> how close (or not!) I got :)
> 
> > I will confirm this tomorrow, I left the sheet with results at home. Keep
> > in mind that this is heavily modified 2850 with water cooling, so I saved
> > 50-100W (low-high speed) on fans.
> 
> Just imagine the worldwide power savings if Dell offered it as a standard 
> accessory. How many PEs are there our there?
> 
> Cheers, Kuba
> 
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