Grub uses the old VGA driver and can not handle the 290x @144hz. It's the same
issue with the opensource which works correctly only @60 Hz...  I fixed the
problem by forcing a resolution with grub. 

But impossible to solve the issue with the xf86-video-ati driver. Also tried
the git version.

Remember, no issue with windows & linux with Catalyst fglrx driver so I do not
trust a hardware issue.
There must be a diff�rence in refresh rate management if catalyst wedge to
144Hz immediately after installation while the opensource driver made a bizarre
139Hz with artifacts (see attachments).

Can be an important point to clarify: I use DisplayPort 1.2.