AMD doesn\'t include an heatspreader like Intel does to keep the cost down.
Also, if the CPU over heats the system crashes, most people don\'t leave their computers on when it crashes so the risk of the core actually melting isn\'t that great. But when it comes to the older Tbirds, if you start with out a heatsink or one that hasn\'t been properly seated the core will melt with in 8 seconds. The AthlonXP (based on the Palomino core) deals with heating a llot better than the Tbird\'s.
There was a video where some guy played a game of Q3A on a Palomino (AMD) based system using passive cooling only. It ran fine. Ofcourse I don\'t reccomend this since it is a fact that Athon\'s get hotter. Due largely to the fact that there is a large transistor count running at a very high clock speed.
EmperorRob, it\'s true that it\'s easly to crush the core of a Tbird, since AMD doesn\'tinclude an heatspreaded, and leaves the core naked.