audiophyl is awesome. After trying no fewer than four separate HOWTOs online for this very problem, I ran through his guide without a hitch and now have both direct rendering and OpenGL functionality on my Rage Mobility card for this Compaq Armada E500, a problem I had thought was insoluble.

glxgears gives me a framerate of more than six times what I had previously, and the OpenGL screensavers I've tested look gorgeous. I'm now about to install Quake II in order to play it as God intended it.

Thank you very much audiophyl, it's folks like you that make the free software community great.