Comment 31 for bug 344252

For comment #27, #28 - I have an Optiplex GX270 and a laptop which can't be set to ondemand or conservative. It seems to be a problem with any computers I have which use p4_clockmod - try:
$lsmod | grep p4_clockmod
The only workaround I've found is to install and start powernowd with the system, and set the governor to userspace. This is set in arch in the /etc/conf/cpufreq.conf file (sorry, don't have the details for Ubuntu). I think you could put "cpufreq-selector -g userspace" in /etc/rc.local or a runlevel script in ubuntu.