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Re: Searching Tool for CPU stepping down

On Thu, Jul 27, 2006 at 07:14:00PM +0200, Hans-J. Ullrich wrote:
> today I have an unusual thouhgt: I am looking for a tool, which I want to 
> start on the notebook, when doing nothing. I do NOT mean powernowd, cpufreqd 
> or similar, which use the pins on the cpu to switch it down (on my AMD-Turion 
> to 800MHz) I am looking for a tool like those on windows in the early 486er 
> days: they were called "waterfall" or "raindrop" and could change the 
> cycle-rate from i.e. 100 MHz to 10 MHz. 
> Does somebody know such a tool for linux ? Or is this on modern cpus not more 
> needed !

You just described cpufreq. Just use a kernel with cpufreq support and
use the "ondemand" or "conservative" governor to let the CPU switch to
various frequencies.

Note that you can't decrease the clock frequency on a 486 without
extensive hardware support on the motherboard. Some 486 notebooks had
such hardware (my old Digital notebook, for example), but the
programming interface was non-standard: the Digital tools certainly
didn't work on Compaq notebooks.

> I imagine, with these tools, power would last much longer, when I can bring my 
> processor down to 100MHz.
> Or do I think wrong ????

Yes and no. Subtle detail: you don't want to save power, you want to
save *energy*. See my OLS 2002 CPUfreq paper:



+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands

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