Custom Resolution Utility (CRU)

[ToastyX]

"LCD standard" allows the video card to clock down normally when idle, but it uses a lot of bandwidth. If "LCD standard" works for you without artifacts, then you're lucky. Most people have to use "LCD reduced" to get a stable 2560x1440 @ 120 Hz, and some monitors can't even handle that.

NVIDIA cards are more tolerant of lower blanking periods, so you can probably reduce the vertical total to 1475 while still allowing it to clock down. Horizontal total can be set to 2704. That will reduce the bandwidth needed and provide a more stable signal when dealing with such high pixel clocks.