Hey, I recently got a 2015 13" Macbook Pro with basic spec (8GB RAM, 128GB SSD, 2.7 GHz i5). Yesterday I hooked it up to my 4k display via Displayport (60hz seems to be working). It doesn't run smooth at all. I can understand that 4k Youtube is a problem due to the missing h265 decoding function of the processor, but even the UI lags really bad (scrolling, animations when you minimize windows, open the mission control etc.) I'm using MacOS 10.12.5 and already cleared the NVRAM stuff. Is there a solution or is the device really unable to cope with 4k?