powerd effectiveness

Mike Jakubik mikej at rogers.com
Wed Jan 11 19:21:39 PST 2006

Daniel O'Connor wrote:
> On Thu, 12 Jan 2006 10:57, Mike Jakubik wrote:
>> It seems that powerd does very little in terms of reducing heat, and
>> sacrifices performance while doing so. Am i wrong to assume that
>> lowering the cpu's frequency should reduce consumed power, and therefore
>> reduce the amount of heat produced? I have tested with mbmon and i see
>> no difference between an idle system running with powerd at 75mhz, and
>> at full rate without. Also, while testing the speed of a php script, i
> If you want to test how much heat your system draws for a given clock speed 
> you should dispense with powerd and just set the frequency by hand, ie..
> sysctl dev.cpu.0.freq=XXX
> powerd won't run your CPU at a specific clock frequency - it varies the CPU 
> frequency based on current load conditions.

The load was 0, only thing that was running was mbmon.

> Do you have thermally controlled fans? If so I wouldn't expect the temperature 
> to vary with clock speed very much at all.

No, i do not.

> The powerd defaults do not change frequency that quickly - every 500ms by 
> default. I run it with '-p 200' and it seems fine although you do notice it 
> 'stick' sometimes (where the CPU change doesn't happen quickly enough).
> You could try what I do but there are some systems which are very slow to 
> change clock speed so this could be an impediment.

What was part of my question, is it the hardware or the software thats 
at fault here. I.e. would a cool n quiet system be better.

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