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 <email@example.com> 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,
> > 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
> on CPU load? That's what I need in the first place. Compiling should
> 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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