I can has heat dissipation? To keep the iMac cool and happy, Apple's included six temperature sensors, three fans, and two gigantic heat sinks.

To put the massive size of the heat sinks in perspective, check out the relative size of the USB ports on the bottom left of the board.

Notice the PRAM battery on the logic board (circular silver disc) for storing date and time when the power is disconnected. When changing the battery be careful to not to force the plastic top that holds the battery into place.

The processor is socketed, but there's a "Warranty void if removed" sticker above one of the heat sink's screws.