After installing Apple's CHUD tools (explained in the middle of
this page), users have discovered the "Nap" preference setting in the Hardware preference panel. Enabling this setting can lower operating temperatures and heat in your system by cycling down the CPU during idle time. However, rebooting the computer resets this setting. By adding this little AppleScript to your login items, you can create a permanent setting for this.
-- Install Apple CHUD
-- This script enables processor NAP mode for power savings
--
do shell script "hwprefs cpu_nap=1"
[
robg adds: I haven't tested this by restarting, but I do seem to recall that the Nap setting was lost after the 10.3.4 update reboot...]