SteamOS update adds AMD graphics support
During CES 2014, Valve and Intel announced that SteamOS had gained native Intel support. Valve also said that the equivalent AMD support would follow shortly - and now it has, arriving with the latest update. When first released, SteamOS was only out-of-the-box compatible with Nvidia. None of this matters to you yet, I suppose, unless you're one of the lucky few with beta access to the new, Linux-based operating system.
Thanks, Polygon.