I was trying to install DaVinci Resolve on a desktop with oldish onboard AMD graphics (Radeon 3000 / RS780L) and was so incredibly lazy that I downloaded and installed CUDA (from NVidia, and a 1.5G download into the bargain) before deciding to look at the back of the case and check lspci to see what I had. I waded through a whole bunch of packages trying to get enough graphics functionality for Resolve to work, then gave up. I noticed that my KDE display settings were pretty mangled. The monitor was listed as "default" and the resolution was locked in at an ugly 1400x1050 and 77Hz, no other options. xrandr said the same. The monitor itself claimed it was doing 1920x1080 and 60Hz.
I spent a very long time thrashing the interwebs looking for a way to reinstall the appropriate driver (https://help.ubuntu.com/community/RadeonDriver). Eventually I stumbled across this old ArchLinux forum post (https://bbs.archlinux.org/viewtopic.php?id=166037) and tried a few of its suggestions. I removed "nomodeset" (something that had been suggested in the course of trying to get Resolve to work) from the /etc/default/grub file and updated grub. What definitely fixed it was issuing the command "modprobe radeon modeset=1". That kicked me out of my KDE session and let me log in at glorious 1920x1080. I rebooted the system just to check and apparently the change is permanent.
Just in case someone else screws up an old AMD graphics setup just this badly.
I spent a very long time thrashing the interwebs looking for a way to reinstall the appropriate driver (https://help.ubuntu.com/community/RadeonDriver). Eventually I stumbled across this old ArchLinux forum post (https://bbs.archlinux.org/viewtopic.php?id=166037) and tried a few of its suggestions. I removed "nomodeset" (something that had been suggested in the course of trying to get Resolve to work) from the /etc/default/grub file and updated grub. What definitely fixed it was issuing the command "modprobe radeon modeset=1". That kicked me out of my KDE session and let me log in at glorious 1920x1080. I rebooted the system just to check and apparently the change is permanent.
Just in case someone else screws up an old AMD graphics setup just this badly.