powerd effectiveness

Daniel O'Connor doconnor at gsoft.com.au
Wed Jan 11 18:56:29 PST 2006


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.

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

> found myself refreshing it quickly in the browser to see the results of
> the timers. I was getting sporadic results, on an otherwise idle system.
> I noticed that if anything cpu intensive ran in the background, my
> script would execute quicker. I disabled powerd and restored the
> frequency, at this point i got more consistent results, and the script
> would execute over 100msec faster. It seems like its not adjusting the

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.

> clock fast enough. Are these problems with powerd or just my hardware?
> It is an old athlon system, running on the via133 chipset .

I'm suprised a system this old even supports a clock speed as low as 75Mhz.

-- 
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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