Quote Originally Posted by tormod View Post
Boot with radeon.modeset=1 to use KMS and with radeon.modeset=0 to run without. Official Ubuntu kernels currently default to 0, the xorg-edgers kernels default to 1.

If you have an AGP card, you can force the AGP mode with radeon.agpmode=X where X is 1,2,4,8 (same as the old AGPMode option in xorg.conf, see "man radeon"). You can turn off AGP (and force PCI instead) with radeon.agpmode=-1.

"modinfo radeon" lists all options for the radeon module. For general boot options, see https://help.ubuntu.com/community/BootOptions

Ignore the "unknown option" warning, it is a false warning.
try writing agpmode=-1 - at least for me radeon.modeset=1 did not work for the official kernel, but modeset=1 did.