cpu frequency scaling not supported on TC4400

[Dominik Stockinger]

Hi,

I installed various Linux distributions on my HP TC4400 tablet with T2500 dual core cpu. In all cases I could not get cpu frequency scaling to work. The distributions I tried were Ubuntu 6.10 (with linux kernel 2.6.17) and OpenSUSE 10.2 (kernel 2.6.18) and a new Fedora version.

I would greatly appreciate any information on why this problem exists and how I can solve it. Under linux my battery lasts approx 2:30 hours while under Windows XP the battery lasts approx 5 hours.

In detail, what I see is the following (the same situation for all the tried linux distributions):

- I would expect a directory
/sys/devices/system/cpu/cpu0/cpufreq/
but this directory does not exist

- lsmod lists the following modules which are related to cpufreq: cpufreq_usedspace, cpufreq_stats, freq_table, cpufreq_powersave, cpufreq_ondemand, cpufreq_conservative, speedstep-lib. modprobe on any of these does not show any error messages.


- dmesg showed the following information that might be relevant:

[17179571.852000] ACPI: Looking for DSDT ... not found!
...
[17179573.688000] CPU1: Intel(R) Core(TM) Duo CPU T2500 @ 2.00GHz stepping 0c
...
(and similar for CPU0)

- trying to run e.g. powernowd or gnome's frequency scaling monitor results in error message "cpu frequency scaling not supported".

I would be very grateful for help and of course I would be happy to provide more detailed information!

Dominik