Using CHUD and enabling Nap Mode

Need to cool down a hot processor?
Are the fans of your MDD driving you crazy?
Is your machine freezing due to high CPU temperatures?

An excellent way to cool a hot machine is to throttle down the processors by using CHUD Nap mode.

CHUD is available in the XCode Developer tools.
This is available to all, but must be installed from your OS X Install disc.
For single processor machines, the 4.x versions of CHUD work fine.

For Dual processor machines, CHUD 3.5.2 is considered as the last version to support nap in dual processor MDDs.
However, I have received reports of nap enabled successfully in a dual 1.25GHz MDD running Leopard and CHUD 4.4.4

“What exactly is nap mode doing that allows the processor temp to drop so much? Am I losing performance by doing this, or is it just making the CPU run that much more efficiently? “

You can liken it to the accelerator pedal on a car engine. Push the pedal, and the engine speeds up. Take your foot off the pedal, and the engine slows down.

Nap Mode simply allows the CPU's to slow down when they can, rather than run at full speed all the time.
The slow down, or nap, reduces the power consumption, thereby the heat produced.

There isn't any performance hit by using nap mode. CPU response is instantaneous.
In fact, because the CPU's operate at lower temperatures, on average, performance is most probably helped by using nap mode. Hot processors don't work as well...... 

“How do I install CHUD?”

Run the Deinstaller first, just to be sure there are no previous versions on your machine. Then, run the installer. After installation you´ll get a preference pane in your System Preferences/Hardware/Processor, where you can easily toggle on/off the NAP feature.

This shows Nap mode enabled for my PowerLogix processor in Leopard, 10.5.6, using CHUD v4.2.0

Scripts to enable Nap mode automatically

OS X Tiger
Install Apple CHUD
This Applescript enables nap mode.

do shell script "hwprefs cpu_nap=1"

Save the AppleScript as an application and add it to the list of login items for your Mac OS X user account.

Here are scripts that one can install in Startup items:

Courtesy of Nick and Mike of

i blog, therefore i am.
Sunday, August 16, 2009