RE: UP3214Q - no picture after powering off the device / half picture at the login screen
@E.T. you seem to be the only one with an ATI setup - do you have any no picture issues after a display power off and on if the PC stays on?
The weird resolutions IMHO are due to the tiling. In DP 1.1 mode you can (by defining custom resolutions in the nvidia cp) create proper 16:9 resolutions, something which doesn't work in DP1.2 (either due to the hardware not supporting it, or driver issues). If you look at the resolutions your display reports to windows, they seem to be mostly lower versions of what one tile (screen half) can do.
I'm hoping that the influx of cheaper 4K screens will force hardware and software makers to make this setup more reliable as right now it seem hit and mostly miss
I have almost no issues when waking up from sleep mode, only one time it reverted back to 1920x2160 (one screen), but 99% of the time it's ok.