I've got a dell p2715q 4k monitor that I connect to MBP (mdp to dp). It works at 4k in Yosemite @ 60Hz, but maxes out at 1440 in bootcamp windows 8.1. I can use a hdmi on windows at 4k 30Hz but I can't get the display port 4k 60hz to work on windows. Any ideas? I have updated iris drivers .