estherau posted at 8:20AM Sun, 13 September 2015 - #4228046

We can use either nvidia or ATI on a mac. not only that it has thunderbolt ports so an external chasis can be connected ie eGPU if one is keen and has enough money for that.

If you're trying to be cost effective, you're buying the appropriate hardware. You can use thunderbolt, but is it going to be as effective as a gpu installed internally? Most likely not. Those macs will probably be ditched for GPU render farms.