I tried your command:
My processors are still running at 2900 MHz.
sudo TurionPowerControl -set core all pstate 0 frequency 2500 -fo 0
To monitor that, I am simply using Folding@Home. The time per frame is exactly the same before and after I entered the command, so I would say no modification has been made.
I can also check that it is not working by putting something like:
Which should freeze or reboot my computer since such a frequence is not possible.
sudo TurionPowerControl -set core all pstate 0 frequency 4000 -fo 0
Moreover, I gave a try to K10ctl, and I see the same problem. Everything seems to work, but the benchmark show no modification of the speed of the CPU.
I am trying to think that my motherboard is the limitation. The NorthBridge is Nvidia MCP55. Is it a problem? TPC and K10ctl are modifying the motherboard or directly the CPU?