gil999It's good enough to handle 4k@60Hz. I'm not sure about the included HDMI cable though, I can only get 4k@30Hz with my 980Ti. I am ordering a HDMI 2.0 cable to give it another try.
update on August 25, 2016:
I do get 4k@60Hz from a Amazon Basic HDMI (high speed, but claimed version 1.4) by turning on the "Deep Color" option.