I have a 290, monitor benq xl2411t.

Pushing high resolutions both in grub or xorg file produces glitches. They are
very noticeable at 120/144hz less noticeable at 100hz but still present. They
appear if I set `video=1920x1080@120` option at boot time, or add a modeline
with cvt in a xorg .conf file.

However if I remove the modelines from the conf file and just do a `xrandr -r
100/120/144` I have no glitches at all with any resolution. 

Setting a modeline with `cvt -r` also works, of course the only other mode
possible is 120 because it requries multiples of 60 but it has 0 glitches and
it works even buy setting it in the .conf file