Jason O’ Grady writes on ZDNet how you can significantly lower heat dissipation on your Core Duo powered MacBook or MacBook Pro by reducing the CPU voltage.
By lowering the voltage to the processor you can not only drastically lower the heat dissipation, but also increase the battery time significantly. There are, believe it or not, no downsides with this method, if you do it right.
However, OS X (and practically other OSes, too) don’t have built-in software to manage the CPU voltage arbitrarily, but fortunately, there are third-party software that let you do this.
CoolBook is a $10 shareware application for the MacBook and MBP that allows you to adjust the frequency (clock speed) and voltage of Intel Core Duo and Core 2 Duo CPUs.
According to the author’s published benchmarks his MacBook (1.83GHz) temperature decreased by as much as 14Â°C (25.2Â°F) just by dropping the voltage from 1.2125 V (Apple default) to 0.95 V (the minimum).
Apparently, Core 2 Duo-based ‘Books don’t need the cooling-down benefit from undervolting, but if you need the extended battery life, then this might still be worth the try.