I have a k4200 GPU and 2 Acer XB270HU monitors on a system running Centos7. I have tried using drivers 346.72, 349.12 and 352.09 to get these displays to run at 120Hz. The best I have managed is 85Hz. Choosing either 100 or 120 Hz ends with the monitors in standby (I can return to a terminal and re-edit the xorg.conf to get back to working at 60/85Hz). If I choose 144Hz, then the monitors are blank, but suggest they are receiving a signal (blue light still on) but the machine does not respond to keyboard any longer.
I have tried to generate modelines manually but it rejects them as not being valid and then goes into some auto mode. If I turn off EDID (Option “UseEDID” “False”), then it only rejects the 100Hz and 85Hz modelines and accepts the 60Hz modeline, but the screens are blank and in standby . . .
Has anyone had any success with these monitors ? Any suggestions as to how to generate valid modelines? I have just been using the online XFree86 Modeline Generator site, but maybe I have some of the info wrong. The manual says the Dot Clock is 540MHz, but the Xorg.0.log reports it at 960Mz . . .