The front side of the port board:

PLX Technology PEX8723 PCI Express Switch

Intel DSL5520 Thunderbolt 2 Controller

Cirrus 4208-CRZ Audio Codec (seen in the MacBook Pro 15" Retina Display)

Intersil 14AIRZ F335QV

Texas Instruments 58888D

Texas Instruments 58872D

Also along for the ride is a standard BR2032 CMOS battery.