Apple's iterative streamlining is again in effect, with a slimmed down and beautified CPU heat sink.

We compared this new heat sink to last November's bigger, beefier, and more securely-fastened spidery mess, and started to wonder what changed to allow such a slender 'sink.

The truth was alarming—the CPU is soldered in place on the logic board, and cannot be removed, replaced, or upgraded.

As far as we can tell, this is the first aluminum iMac to have a soldered CPU; it's a silent, but clear, shift to even poorer iMac upgradeability.

21.5-inch: 2.9GHz corei5 CPU is upgradeable and the double side sticky strips for the the 2012 model work on this late 2013 model as well.