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Re: ACPI on IBM Thinkpad T30

Am 2003.11.19 09:48 schrieb(en) Serge Gebhardt:
 > On Wed, 19 Nov 2003 00:18:22 -0500
 > Mike Phillips <phillim2@comcast.net> wrote:
 > > Non ACPI just gives you two speeds to work with, full 1.8 and slow
 > > 1.2.
 > >
 > > echo "1200000:1800000:powersave" > /proc/cpufreq.
 > > echo "1200000:1800000:performance" > /proc/cpufreq to restore.
 > awesome. It seems I can even get it down to 250 MHz. The system would
 > get really slow and /proc/cpuinfo would show the right frequency. But
 > when measured with specific tools (eg x86info), they all find the
 > CPU running at 2GHz (I have a 2GHz T30). These tools do not just read
 > the identifier, they actually _measure_ the frequency.

Yes, but I noticed, that this measuring is sometimes not that effective.
For example I use the gkrellm-gkx86info - plugin and even on a non-cpu- scaling kernel it shows frequencies that can't be true (e.g. 1200 instead of 1800MHz on my Athlon mobile)

 > > You can actually tweak the cpu through the acpi interface too:
 > >
 > > echo "N" > /proc/acpi/processor/CPU/throttling where 0 <= N <= 7.
 > >
 > > This really does work, try it with "7" and watch the system crawl,
 > not
 > > sure if this saves any power though.
 > This seems to just throttle the CPU by putting load on it. After
 > `echo 7 > /proc/acpi/processor/CPU/throttling` the system becomes
 > really slow because of CPU load. It is certainly not the best way to
 > save power :)

No, it's no cpu-load but only cpu-time that is "wasted" with doing nothing - so it feels slower and don't get that hot.

> But are there some daemons around, which switch the frequency depending > on CPU load? That's what I need in the first place. Compiling should be
 > really fast (2GHz) but I don't mind having the CPU at 250MHz while
 > working. The switch should automatically be done in background.

Yes, powernowd does it in a great fashion. It's now avaiable in unstable! - it also supports speedstep :)

But you have to compile in the "userspace-governor". (Power Management -> CPU Frequency -> Frequency Scaling -> userspace governor
And to be sure also the old 2.4 /proc/sys interface...

Than cpudyn works as well and you also get /sys/.../scaling_avail_freq


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