You mean to say DisplayPort 1.2, which is supported by Thunderbolt, does not have enough bandwidth. The iMac will need to support DisplayPort 1.3 for ultra high res displays. That is why Apple had to build their own controller for the internal display in the retina iMac. The Mac Pro has Thunderbolt 2 ports, and can drive 4K displays, but they also have the FirePro cards which are capable of doing it.
11/10/14 at 10:31am