iFixit posted a teardown of the new iMac 21.5"

Swimsuit season may be over, but Apple's new Late 2012 iMac has been working on its beach bod. Slimming down to a wafer-thin 5mm at its edges, the newest iteration of iMac is by far the slimmest of its kin. We are very curious what sort of diet could cause such a drastic change, so we opened it up to find out!

Step 1 — iMac Intel 21.5" EMC 2544 Teardown

It may not have a Retina display, but the new 21.5" iMac has some commendable specs:
2.7 GHz quad-core Intel Core i5 processor with 6 MB L3 cache
8 GB of RAM
1TB hard drive (5400 rpm)
NVIDIA GeForce GT 640M graphics processor with 512 MB dedicated VRAM
Four USB 3.0 ports and two Thunderbolt ports
802.11n Wi-Fi and Bluetooth 4.0

  iMac Intel 21.5" EMC 2544 Teardown