Cramming an ever-increasing amount of resistors, diodes, and transistors into a shrinking die is known as the art of semiconductor engineering. As these microprocessors tack on an additional 66 or 100 MHz with every upgrade, those tiny electrical parts put out more and more heat. The biggest heat culprit is AMD's K7 Athlon Thunderbird core screaming at 1.4 GHz. You'll need a trusty heatsink and fan (aka HSF) to keep that thing from burning up. OCZ Dominator review