When I try to choose 120hrz on on my XL2720t my screen crashes to a blue screen. Not the BSD but just plain dark blue. I have 2 EVGA GTX 560's in SLI. I have the latest Nvidea Drivers. I am only able to get to 100Hrz without crashing.
AMD FX 8350
16 gigs of ram
seasonic ss-1050xm 1050 Watts Power Supply
The monitor or cable may be on its last legs…what cable are you using to connect the monitor?
It’s gonna depend on which cable you’re using. If it has white ends with screws, thats a DVI-D cable. If its black and kinda latches in, its a displayport cable. Either one you should be able to locate locally.