Double-check that CPU frequency scaling is enabled and set to OnDemand.
The following directories should exist:
If they don't exist, enter modprobe powernow-k8
as root to enable CPU frequency scaling on your AMD CPU.
Each time, the output should be "ondemand." If it's not, enter:
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
Put the echo commands, and the modprobe command if needed, in your startup files.