CPU throtteling on Notebooks (where is the option gone?)

[rembrandt <rembrandt@jpberlin.de>]

I can remember that it was possible on 3.4 to throttle the hw.cpuspeed.

But on 3.5 it seams so that I'm not able to change the cpu-speed nor
using Pentium-Mobile feautures.

As root on 3.5 and my Notebook:

# sysctl -a hw.cpuspeed
hw.cpuspeed=1600
# sysctl -a hw.setperf
hw.setperf=100
# hw.setperf: 100 -> 50
ksh: hw.setperf:: not found
# hw.setperf: 100 -> 50
ksh: hw.setperf:: not found
# hw.cpuspeed = 1200
ksh: hw.cpuspeed: not found
# sysctl -w hw.setperf=50
hw.setperf: 100 -> 50
# sysctl -a hw.cpuspeed
hw.cpuspeed=1600
# 

Did something changed or did I remember the wrong commands to use that feauture?