My assembled PC is connected to a Samsung U28E950D 4K monitor. The motherboard is Gigabyte Z170 Gaming 7, it is using the intel 6700K integrated graphic. When I connect it through DisplayPort 1.2, the monitor just doesn't sleep properly. I set the "turn off monitor" timer in Windows 10 at 1 min to test it, the monitor does go into the standby mode, but a second later it turned back on itself with black blank screen and DisplayPort channel sign on the top right corner. Then it shut down again before going into an infinite loop like this. However, when connecting through HDMI 2.0 it behaves normally. I've updated to the newest driver and turned off OC and set the Bios to factory default (I even reset the CMOS and reinstalled the OS). I'm not sure whether the DisplayPort on the motherboard or the Monitor is the culprit. I just have to use DisplayPort as its colour is brighter than HDMI 2.0.