I have a Sonnet Echo Express III-D Thunderbolt to PCIe Card expansion chassis connected to Bus 2 on my new Mac Pro. There are no other devices on this bus. I purchased it with the Thunderbolt 1 card and received the Thunderbolt 2 card today. I used Black Magic to test the speed of my Samsung EVO 840 1TB SSD installed in the expansion chassis using the Sonnet Tempo SSD Pro. I have attached screen shots of TB1 and TB2 tests. As you can see no difference in performance.