[maemo-developers] Frequencies scaling with OS2008

[From: Krischan Keitsch]

Hi,

I read an interesting thread about overclocking the n800 [1]. Based on that I 
started experimenting with the n800 running OS2008. The OS scales the cpu 
frequency nicely from 165MHz up to 400MHz.

The current cpu scaling can be checked with

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

So far so good. I noticed that during playback of mp3 files the cpu is scaled 
to 330MHz. Stressing the cpu during mp3 playback will not change the 
scaling - the cpu will not scale up to 400MHz. 
According to a presentation "Nokia Internet Tablet Power Managemen" [2] the 
dsp runs at 220MHz when the cpu is set to 330MHz.
(This is the default setting in OS2007, by the way.) 

I was wondering if the device really needs to run at 300MHz (220MHz dsp) for 
mp3 playback? Is the max dsp power needed for such a task? Or would 220MHz 
(177MHz dsp) or 165MHz (85MHz dsp) be sufficient? Would a lower dsp scaling 
save even more battery?

Has anyone managed to successfully change the settings manually? 

Best regards 
Krischan

[1] 
http://internettablettalk.com/forums/showthread.php?t=10681&highlight=overclocking

[2] http://maemo.org/news/announcements/view/1184097560.html
Nokia Internet Tablet Power Management by Klaus K Pedersen, Igor Stoppa