@kevin_intel: which screen do you have? UP3214Q, UP2414Q or something not from Dell?. If Dell, REV A00 or A01? Also, your desktop board means you have a desktop CPU, isn't there a difference between the graphics engine in a desktop CPU and the Haswell U series? I know that at least resolution wise, the U and Y models cannot handle 3840x2160@60. If I look at the datasheet of the desktop Haswell line (https://www-ssl.intel.com/content/dam/www/public/us/en/documents/datasheets/4th-gen-core-family-desktop-vol-1-datasheet.…) it states full 3840x2160@60 support (e.g. in table 9).The Ultrabook line datasheet lists a lower resolution. I don't know if that's relevant but something is different between the U part and the desktop parts as far as the GPU is concerned.
I'll get the chance to test another UP3214Q over the week-end, and I could reconnect my U3014 (hasn't had any sleep issues with the June beta drivers on the U3014)
What power settings are you refering to?