Messages in this thread | | | Date | Sun, 01 Jun 2008 21:36:58 -0500 | From | Roger Heflin <> | Subject | Re: 2.6.25.x: Wrong CPU frequency (cpufreq table) with p4-clockmod |
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Arjan van de Ven wrote: > On Sun, 1 Jun 2008 23:57:14 +0200 > Guntsche Michael <mike@it-loops.com> wrote: > >> On May 30, 2008, at 16:07, Guntsche Michael wrote: >> >>> I am most interested in keeping the temperature of my CPU down, >>> which means slower fans, which means less noise. >>> The main "problem" I have is that I do not know if this is a >>> simple display issue or if I am having a more fundamental problem >>> here. >> Just FYI I found out the cause of my problem. >> >> Reverting >> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=ed9cbcd40004904dbe61ccc16d6106a7de38c998 >> this patch resultsin the correct numbers for me. >> >> <cpuinfo snip> >> processor : 0 >> vendor_id : GenuineIntel >> cpu family : 15 >> model : 1 >> model name : Intel(R) Pentium(R) 4 CPU 1.70GHz >> stepping : 2 >> cpu MHz : 637.500 >> <snip> >> >> This patch was reverted because other people seem to have problems >> with it, reverting the revert does not look like a good idea either. >> But since I know now, that this is just a "display" problem and >> everything is working otherwise, I'll just patch this locally for my >> machine here. >> > > just as a side note.. you do realize that with p4-clockmod, your cpu is > still running at 1.7 GHz right? (it's just doing less work '-)
From my testing, I believe the only thing that p4-clockmod does is forces an idle call when it could otherwise do work on an active process, so fullspeed and idle uses *EXACTLY* the same amount of power as p4-clockmod slower speed and idle (and therefore generates exactly the same amount of heat), the only power difference would be that if you were using p4-clockmod to slow down the cpu when it had an active running process (force the cpu to be idle a lot of the time even though it has work). Arjan's point is that if you are using p4-clockmod to slow down an idle cpu in hopes of saving power when the cpu is not being used, then it is not going to make *ANY* difference in the power usage at all.
I tried it on my p4 here, and cannot see any power difference in idle/fullspeed and idle/slowspeed, this is unlike the later power saving stuff that actually does slow down the cpu frequency, and you can measure a different amount of power usage with the different clock speeds and an idle cpu.
Roger
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