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SpeedStep is a technology from Intel to throttle the CPU's clock speed when it is not fully utilized in order to save power. This is especially useful for mobile devices and servers.

On a PureDarwin system, you can use the VoodooPower kernel extension in order to use SpeedStep.

On Intel Atom systems, PureDarwin 9 is known to work well with the VoodooPowerMini.kext (Leopard version) that. (On PureDarwin 10, you'll use the Snow Leopard version instead.)

You can download it from

After downloading VoodooPowerMini.kext, you can install it on your PureDarwin 9 system:

sudo chown root:wheel 755 VoodooPowerMini.kext
sudo chmod -R 755 VoodooPowerMini.kext
mv VoodooPowerMini.kext /System/Library/Extensions/
kextload /System/Library/Extensions/VoodooPowerMini.kext
# Rebuild kext cache with kextload

Now, you can verify that it is working:

toor@PureDarwin:~% sysctl -a | grep cpufrequency
hw.cpufrequency = 800015400
hw.cpufrequency_max: 1600030800
hw.cpufrequency_min: 800015400

If hw.cpufrequency is lower than hw.cpufrequency_max in low-CPU usage situations, then SpeedStep is working correctly.