New MacPro, many thunderbolts and Video Cards

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
x1 250MB/sec 500MB/sec 1GB/sec
x2 500MB/sec 1GB/sec 2GB/sec
x4 1GB/sec 2GB/sec 4GB/sec
x8 2GB/sec 4GB/sec 8GB/sec
x16 4GB/sec 8GB/sec 16GB/sec

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.


  1. playfans
    June 13th, 2013 | 5:16 pm

    Does TB external GPU work using TB under OSX ? I thought eGPU was still not officially supported. :s

    I hope to see some improvements on that subject, there’s a lot of potential.

    Thanks for the article !

  2. Antoine
    June 15th, 2013 | 7:24 pm

    netkas, although i think that this machine is faded to fail due to unexpandability of it’s main components, there is something else i have seen on these thunderbolt ports:
    In the future, drivers and firmware updates could be created to allow these ports to become a demux/remux of a/v signals.
    besides they being digital, It could exist the possibility to create a gpu “Dock” bellow the machine, connecting to it through some of it’s tb ports and using the internal hardware to re-pass the stream?

  3. scalar
    September 29th, 2013 | 11:28 pm

    We don’t yet know how the AMD cards will be mounted, if they opt for a frame that houses a normal GPU then worrying about external GPU’s and TB 2.0 is pointless (unless you’re thinking of future expansions for iMacs & MBP’s?)

    Anyway I’m amazed that everyone hasn’t just owned up to the fact that the new Mac Pros are 4K/8K video boxes and nothing else (editing, color correction, compositing etc). The ENTIRE reason for TB 2.0 was to enable 4K displays over DP 2.0 so you don’t have to use the 2 port tiling methods nvidia & AMD only recently enabled…

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