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Old 04-18-2006, 10:05 PM   #1
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cpufreq and acpi thermal zones

I have a sony vaio laptop with an Intel P4 processor.
I have been playing with the kernel modules and userspace tools for cpufreq, but have become quite discouraged as everything I seem to do with cpufreq seems to be overridden by thermal controls elsewhere (I assume ACPI thermal zones). This is pretty annoying when my 2.4GHz processor gets knocked down to 900MHz to cool it off 1 or 2 degrees.

Basically what is happening is that the processor will get throttled down if it hits 72deg Celcius. If I compile the ACPI/Thermal as a module, and unload it, I can use cpufreq to keep the processor at full speed (2.4 GHz) and it seems to peak at about 74deg Celcius (I can tell by quickly inserting the thermal module and checking temp)

What I am wondering is if there is anywhere on the system that I can change the thermal zones. I have looked through the module src for thermal.c as well as all of the cpufreq modules and cant seem to understand it enough to actually change the way the modules work. I tried using CPUfreqd, but it just gets overridden too.

Haven't found any similar questions in threads...
Any ideas?

Oh, and yes... I know there is a reason for the thermal zones being the way that they are, but I have done my research and I pretty confident that the zones can be safely changed by a small margin.
Old 04-19-2006, 10:42 PM   #2
Registered: Jun 2004
Location: Lawrence, KS
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Sony P4

Greetings Nic+Tux+Duke

I too have a Sony P4 (GRZ530)laptop. On it, I am using sonypi to control frequency stepping, as well as other things.

With this setup, I have watched temperatures go up and down when comipling a kernal, and it never changes the CPU speed to reduce CPU temp. As the temp goes up, the fan runs faster, and the temp never goes too high.

With a room temp of 71F the laptop runs at 46C to 55C.

Old 04-20-2006, 12:30 AM   #3
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Mine is a PCG-GRZ660 which is apparently notorious for getting hot. The heat-sink was upgraded by sony when the previous owner had it, so it doesnt get as hot as others do, but it is still pretty hot. I have found though that if I set cpufreq with a maximum speed of 1.4GHz then it doesn't hit the thermal trip that would kick it was down in speed. The thermal trip is 72deg Celcius, but this is only the boundary between "OK" and "PASSIVE", and "CRITICAL" isn't until 95deg. I would like to have it not trip until 75deg, as it appears to top out at 74deg if maintaining 2.4GHz.

Oh well, I guess a steady 1.4GHz laptop is better than a 2.4GHz/900MHz laptop.
Old 05-04-2006, 08:32 PM   #4
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ok, so after much experimentation, i have discovered the "solution" for this. since cpufreq seems to be more careful about the temp of the computer than trying to maximize speed, i have come up with the following for those of us who want the maximum speed, but also want to be able to take advantage of cpufreq scaling...

make your cpufreq scaling driver a module instead of built-in. (your specific processor driver, not the cpufreq capability).
when your module is not loaded, the processor will stay in it's current freq. if you insert the module into your running kernel, then you can set use cpufreq scaling.

if you really want, you can also insert the module, set the processor to a specific lower speed, and then rmmod the module and stay clocked at that speed too.

i.e. modprobe p4_clockmod && cpufreq-set -f 1.2GHz && rmmod p4_clockmod

hope this helps someone else too :-D


acpi, cpufreq, kernel, throttling

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