Valve and its partners took the wraps off of an impressive number of Steam Machines earlier this week at CES, and the hardware diversity of the PCs-turned-consoles was one of the most notable things about them. GPUs from Nvidia, AMD, and Intel power all of those Steam Machines, and now the publicly available SteamOS beta has added built-in driver support for AMD and Intel GPUs.
An e-mail from an AMD representative indicated that SteamOS was running Catalyst 13.11 Beta 9.9 drivers and that a standalone driver package would soon be available from AMD's support site. Known issues with the AMD driver as of this release "include tearing and poor overlay performance in-game," problems that will doubtlessly be ironed out in future releases. Intel GPUs are using Mesa 10.0.1, and while standalone Intel and Nvidia GPUs are supported, dual-GPU Optimus solutions still won't work.

Previous builds of SteamOS shipped with Nvidia driver support by default, and all 300 of the Steam Machine prototypes that Valve sent out to testers included some variety of GeForce GPU.