I have just upgraded to Ubuntu 16.04 on my PC equipped with a Radeon graphic card (chipset RV516) and an LCD screen with VGA connector. I was previously using the proprietary driver fglrx but I have read somewhere that it is not supported on recent Ubuntu versions. So I try to use the open driver radeon.
When booting for the installation support, I got a black screen. I had to use option nomodeset to get the installation working. Now this option is in the kernel options set by grub. If I remove it, the black screen comes back.
What is annoying me is the display resolution I currently have, 640x480, while my display can support 1920x1080. I have found information about the xrandr command. Without parameters, This command returns this:
xrandr: Failed to get size of gamma for output default Screen 0: minimum 640 x 480, current 640 x 480, maximum 640 x 480 default connected primary 640x480+0+0 0mm x 0mm 640x480 73.00*
The line about gamma may not be important. The trouble is that xrandr says my screen cannot support more than 640x480. I entered
xrandr --newmode $(gtf 1920 1080 60 |sed -ne 's/"//g;s/ Modeline //p')
xrandr --addmode default 1920x1080_60.00
Now xrandr says:
xrandr: Failed to get size of gamma for output default Screen 0: minimum 640 x 480, current 640 x 480, maximum 1920 x 1080 default connected primary 640x480+0+0 0mm x 0mm 640x480 73.00* 1920x1080_60.00 60.00
This looks better but then I entered:
xrandr --output default --mode 1920x1080_60.00
xrandr: Failed to get size of gamma for output default xrandr: Configure crtc 0 failed
What should I do now the get another screen resolution working?