I recently used a new 2013/14 Mac pro on a project. It was a rental so I don't recall all the specs, but I recall it was the 6-core processor and the D500 graphic cards. I noticed a very odd performance issue that I'm wondering if any others have experienced.
When connecting multiple thunderbolt to DVI dongles to drive 4 screen @ 1920 x 1200 each (three projectors and 1 monitor) the performance in Arena, with almost nothing running at all, was around the 15-20fps mark. As I removed thunderbolt dongles, I could get the fps up again. In desperation, I tried connecting a matrox triplehead2go DP to one thunderbolt port and set the resolution to 2 x 1920 x1200 plus one thunderbolt to DVI dongle. I was still technically pushing the exact amount of pixels as before, but now I was using one less thunderbolt port. The performance jumped up to 50-60fps as I would normally expect.
Any ideas here? It seems that pushing pixels isn't the issue, using a bunch of thunderbolt ports is. Anyone experienced this same behaviour on a mac, specifically the new mac pro?