This e-mail appears to discuss the same problem (at least once he gets glxgears to display four flickering copies):
http://www.mail-archive.com/xpert@xfree86.org/msg11010.html Summary: The 815em is broken under various versions of X, but upgrading the kernel i810 module causes GL to work (and the kernel to panic, but it least it's a start). My various versions: Custom-compiled kernel 2.4.20. xlibmesa-dri/testing uptodate 4.3.0-7 xserver-xfree86/testing uptodate 4.3.0-7 Cheers, Eric