Hi, I've just purchased a new MacBook Pro Retina early 2015 13". Using my old miniDP > HDMI cable I was only able to get 4k@30Hz from the MacBook. My question is. What kind of cable can I use to get 4k@60Hz? Will a miniDP 1.2 > HDMI cable work? Or do I have to get precisely a miniDP 1.2 > DP?