It appears that your setup uses the fbdev module, which should work with a wide variety of GPUs. You can look at the cheatcodes and use some to try specifying a different module to try. Look at the following link for some information: http://www.knoppix.net/wiki/Cheat_Codes Some you might try first would be xmodule=ati or xmodule=radeon. Might even try xmodule=fbxine. They might give you good or absolutely horrible results.

Good luck and be sure to post your results.