I have an 8400GS graphic card, and as I've seen, it has 3 levels of power. Moreover it has a mechanism called powermizer to manage these power states. It automatically switches the card to a lower power state, when it is idle for a few seconds. The problem is that it takes too much time to "warm up", that is, to switch to a performance power state. This makes compiz and other desktop effects unusable. I didn't find a working way to force a fixed power state yet. I also find this card too slow when it comes of any 3d application or effect under linux. I would appreciate any help in tweaking this card for better performance. I am using Ubuntu Hardy on a Dell Vostro 1400.
I have tried options nvidia NVreg_RegistryDwords="PerfLevelSrc=0x2222" in /etc/modprobe.d/nvidia-kernel-nkc. I have also tried to manually load the module and pass this argument. I even tried to set RegistryDwords option in xorg.conf (as some other posts indicate). The X log shows that the driver recognized this option, but with no effect; automatic clock adjusting is still turned on.