The most noteworthy revisions come on the logic board, including the all-new Haswell Core i7 processor, Iris Pro Graphics, and Thunderbolt 2 support:

2.0 GHz quad-core Intel Core i7 processor (Turbo Boost up to 3.2 GHz) with 6 MB shared L3 cache and Iris Pro graphics

128MB eDRAM cache

Elpida J4208EFBG 512 MB DDR3 SDRAM (16 chips for 8 GB total)

Intel DSL5520 Thunderbolt 2 Controller

Intel Platform Controller Hub

Cirrus 4208-CRZ Audio Codec, similar to Cirrus CS4207