Apple does not list the Mac Mini 2014 in above link in the Mac's that can use MST to achieve 60hz on 4K via Displayport. On other places I read that this is due to the limitations of the Intel processor:
This type of resolution is supported on 4th generation Intel® Core™ processor family (Intel® Iris™ Pro Graphics 5200 / Intel® Iris™ Graphics 5100, Intel® HD Graphics 5000 / 4600 / 4400 / 4200) See the following supported screen resolutions through DP 1.2 DisplayPort* 1.2 / eDP* H-Processors: 3840 x 2160@60Hz U-Processors: 3200 x 2000@60 Hz, 3840x2160@30Hz
My question is, if I get a Mac Mini 2014 and upgrade the configuration to 3.0GHz dual-core Intel Core i7, will is still not be able to run at 60hz?
On the Apple site I cannot see the direct difference in processors between the Retina Macbook Pro 15" and the Mac Mini. But apparently the macbook has an 'u-processor' and the mac mini a 'h-processor'?