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Re: CPU power management



On Fri, Feb 16, 2007 at 06:22:29PM +0100, Mattia Dongili wrote:
> On Thu, Feb 15, 2007 at 11:26:24PM +0200, Eddy Petri??or wrote:
> [...]
> > I have installed Debian GNU/kFreeBSD and indeed, the levels are many
> > more than on Linux:
> > 
> > sysctl dev.cpu.0.freq_levels
> > 
> > Results in a list of frequencies down to 31 MHz. I tried some script I
> > found on the freebsd lists[1] to test the speed of blowfish at various
> > speeds and observed that on my Core 2 Duo that:
> [...]
> > In conclusion, it would be nice if this code would be ported to Linux, too.
> 
> AFAICT they are mixing freq scaling and throttling.
> See /proc/acpi/processor/CPU[01]/throttling, I have:
> 
> state count:             8
> active state:            T0
> states:
>    *T0:                  00%
>     T1:                  12%
>     T2:                  25%
>     T3:                  37%
>     T4:                  50%
>     T5:                  62%
>     T6:                  75%
>     T7:                  87%
> 
> and the available frequency steps here are 1.83 GHz, 1.33 GHz, 1000 MHz
> This is a Core2 Duo T5600.
> 
> so eg. at 1GHz I can throttle at 880, 750, 630, 500, 380, 250 and
> 130 MHz.

Oh, and let me add (even if probably aready mentioned): throttling
doesn't save any power, it just idles your cpu. Ok, less heat (no fans,
etc) but the real saving is probably unnoticeable.

-- 
mattia
:wq!



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