I had a similar problem at work getting my external (27" 2560x1440) monitor working with my laptop (a Sony F-series) running Ubuntu. We solved it by lowering th

I had a similar problem at work getting my external (27" 2560x1440) monitor working with my laptop (a Sony F-series) running Ubuntu. We solved it by lowering the refresh rate used by the HDMI output. It took quite a bit of tweaking to find the right values, and frankly I've forgotten what most of it meant, but this may help you: In the "Monitor" section, we defined modelines: ModeLine "2560x1440_33" 164.99 2560 2688 2960 3360 1440 1441 1444 1468 -hsync +vsync ModeLine "2560x1440_30" 146.27 2560 2680 2944 3328 1440 1441 1444 1465 -hsync +vsync Then, in the Screen section, I appear to have modes selected from there: Option "metamodes" "DFP-0: nvidia-auto-select +0+360, DFP-1: 2560x1440_33 +1920+0; # ... and a bunch more that seem to be auto-generated by nvidia-settings? The down side of this is that I can't connect my laptop to use any of our projectors in on conference rooms, but it's a small price to pay in order to be able to drive the larger screen.