I can't seem to find a definitive answer on this. I was using an external 2560 1440 monitor with my Mac and I just bought an LG 4K monitor. I have it connected to my Mac with DP and it is only doing 1920 1080. I am running the Sierra preview and the display settings only give me 2 options - one for native which just does 1920 and another "scaled" option that lets me choose from 2 resolutions 1920 1080 and something else smaller. Can my Mac somehow do 4K even at 30Hz on this monitor and if so how do I do it when the prefs pane doesn't give me any options?