Kubuntu 14.04LTS, Radeon RS690 (X1270), unable to use resolution of more than 1024x768

Solution 1:

Problem solved. Kubuntu 14.04 added a nomodeset to the boot command line (as shown in the Xorg.0.log file).

The solution turned out to be simple. Edit /etc/default/grub and change

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash ro nomodeset video=uvesafb:mode_option=1024x768-24,mtrr=3,scroll=ywrap"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video=radeon"

Then run

sudo update-grub

Along the way, I blacklisted anything that looked like a framebuffer module, but that seemed to make no difference. It may be necessary to make this work, but removing the nomodeset was the final solution.