Comment 77 for bug 36014

I had this problem with a Dell Inspiron 9200 (pentium m 1.7 GHz) with Edgy (kernel 2.6.17-10-generic). But now everything works fine.

I had scaling_max_freq = scaling_min_freq = 600000 and I was unable to change i :

nacim@nacim-laptop:~$ sudo -i
root@nacim-laptop:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
600000
root@nacim-laptop:~# echo 1700000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
root@nacim-laptop:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
600000

As a consequence the scaling didn't work like it used to, about one month ago. I noticed that under Windows everything worked fine but when I played games the GPU was hotter than usual (65°C instead of 40°C). And in fact, the GPU fan didn't work at all. The CPU was also slightly hotter (45°C vs 40°C).

I cleaned my laptop and got rid of the dust that was preventing the GPU fan from spinning. Now, temperatures while gaming are normal. With Ubuntu, scaling_max_freq = 1700000, and the frequency scaling works correctly.

I'm not skilled enough to explain why an abnormally hot temperature of the GPU, or the fact that its fan doesn't spin, makes the CPU run at the lowest available frequency using Ubuntu (scaling worked with Windows). I can only suppose that some hardware device, or the BIOS, gives a wrong scaling_max_freq to the kernel to prevent parts of the hardware from being overheated. But it doesn't explain why, when something goes wrong with the GPU, the CPU is affected.

I hope this will help understanding this bug and the fact that it seems to appear randomly.