Summary: If you have performance problems using the JACK Audio-Connection-Kit and the
fglrx ATI grpahics card driver, switching to
radeon may solve them. Unity 3D and radeon can work, but leftovers of other drivers might get in the way. Also: Proprietary, binary blobs smell bad and Ubuntu’s infrastructure around those drivers is dodgey.
On Ubuntu 11.10, I switched graphics cards and thus drivers from
fglrx without much of a problem.
I recently upgraded to Ubuntu 12.04 and was quite pleased by how smooth that went and glad for not having to reconfigure and reinstall a bunch of stuff. As with every release so far, some issues might have disappeared, but a very noticable new one arrived: focus-follows mouse combined with auto-raise does no longer work reliably. So far I failed to identify the pattern for the cases where windows are not raised, when they should be.
After a while, I wanted to get back to music production with JACK and Ardour. My system was still configured for JACK to run in realtime mode, but I got many disconnects, often right when Ardour brought up its main window. I found out this only happened with Unity 3D, not with 2D. So it seemed like either one or the combination of Unity 3D and the
fglrx driver interfered with realtime mode. A fellow #lad inhabitant knowledgeable about this realtime kernel business suspects that the 3D accleration part of the
fglrx driver is not preemptable.
Where does one even report bugs about that proprietary blob? And how would one diagnose what exactly goes wrong?
Now I could use Unity 2D, but I really miss window drop-shadows, dislike the look and different notification animations for the Launcher icons and hate the fact that the Dash doesn’t react to the same shortcut I configured while using the 3D version.
Initially, I thought I would need the fglrx driver for Unity 3D, but still wanted to try switching to radeon. The Additional Drivers dialog claimed that neiter of the 2 ATI options were active, but
lsmod told me otherwise. I have some Wacom-related stuff in my
xorg.conf, which had to be moved out of the way, to get that thing to work. After a reboot,
radeon was in use, but Unity decided to drop back to 2D. The cause:
Xlib: extension "GLX" missing on display ":0.0". The solution was purging any trace of
nividia(!) from my system. Also, for good measure, but I suspect it’s unnecessary:
sudo apt-get install —reinstall libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core; sudo dpkg-reconfigure xserver-xorg.
Now I have a working Unity 3D, using
radeon, no disconnects or xruns galore using JACK and Ardour. Only new problem so far: shaky mouse pointer on the login screen.