June 13, 2013
Lots of people ask what will happen if they connect videocard over thunderbolt 2 to new MacPro.
Let’s figure that out.
First, what is thunderbolt 2.
In thunderbolt 1, you had 2 lines of bidirectional 10 Gbit/s link, one for video and one for data.
In thunderbolt 2, these lines are combined, now you can get either 20 Gbit/s for data or for video.
That gives us 2.5 Gbyte/s.
now lets looks at pcie
|PCIe Bandwidth Comparison (Each Direction)|
|PCIe 1.x||PCIe 2.x||PCIe 3.0|
so, TB2 is a bit faster than pcie 3.0 x2 or pcie 2.0 x4 (talking about pcie 2.0 because true (old) macpros has pcie 2.0 links)
Now, if you want to know performance impact, open this link for a good article at anadtech and look for red bar.
In games, performance impact could be from few percents up to 40 percents. In opencl workload impact gonna be high.