Can't select 2560x1440 resolution even though I know it's possible (I have proof!)

Solution 1:

Another answer that was also posted here earlier was correct.

Before I start let me say that I have no problem on my Haswell setup with a CS1794 KVM switch and a 2m HDMI cable (ASIN: B003L1ZYYM) connected to the U2515H.

HDMI2 connected 2560x1440+4480+0 (normal left inverted right x axis y axis) 553mm x 311mm
   2560x1440      60.0*+
   1920x1080      60.0 +   60.0     50.0     59.9     30.0     25.0     24.0     30.0     24.0
…

It's a bit different on my Ivy Bridge setup with the same equipment, but I can configure 24Hz and 30Hz modelines with gtf:

xrandr --newmode "2560x1440_24.00"  114.37  2560 2648 2912 3264  1440 1441 1444 1460  -HSync +Vsync
xrandr --addmode HDMI2 "2560x1440_24.00"
xrandr --output HDMI2 --mode "2560x1440_24.00"

xrandr --newmode "2560x1440_30.00"  146.27  2560 2680 2944 3328  1440 1441 1444 1465  -HSync +Vsync
xrandr --addmode HDMI2 "2560x1440_30.00"
xrandr --output HDMI2 --mode "2560x1440_30.00"

And this is what my xrandr output looks like:

HDMI2 connected primary 2560x1440+0+0 (normal left inverted right x axis y axis) 553mm x 311mm
   2560x1440      30.0*+
   2048x1152      60.0
   1920x1200      60.0
   1920x1080      60.0     60.0     50.0     59.9     30.0     25.0     24.0     30.0     24.0
   1920x1080i     60.1     50.0     60.0
   1600x1200      60.0
   1680x1050      59.9
   1280x1024      75.0     60.0
   1200x960       60.0
   1152x864       75.0
   1280x720       60.0     50.0     59.9
   1024x768       75.1     60.0
   800x600        75.0     60.3
   720x576        50.0
   720x576i       50.1
   720x480        60.0     59.9
   720x480i       60.1     60.1
   640x480        75.0     60.0     59.9
   720x400        70.1
   2560x1440_30.00   30.0
   2560x1440_24.00   24.0

24Hz refresh rate is as low a you can go and it feels terrible, 30Hz is just a little bit of improvement. You should get a proper HDMI 1.4 or DisplayPort setup. Even DisplayLink adapters would be worth looking into after they have finally published Linux drivers for their USB 3.0 devices.