Building your own Steam Box just got a heck of a lot easier, because the SteamOS operating system isn't limited to Nvidia GPUs anymore. As of the latest SteamOS release, both Intel and AMD graphics are supported. Mind you, SteamOS is still very much in beta, and the Linux video drivers are in a beta state as well, so don't expect too much. AMD specifically mentions that there are some screen-tearing issues, and that things can slow down when the SteamOS overlay and games are running simultaneously. Valve engineer John Vert writes that the company is still working with Intel and AMD to fix a number of these issues.
That's good, because a number of Steam Machines intend to ship with AMD and Intel graphics at launch, including the $499 iBuyPower box, the $499 CyberPowerPC computer, and at least two tiny Brix boxes made by Gigabyte.
AMD Radeon HD 5000 and up
Supported AMD graphics include the HD 5000 series and up, including an array of desktop, laptop, and embedded GPUs. You can find the full compatibility list here. As for Intel, the company's latest Linux release supported most Intel HD Graphics solutions, but we're not certain which would work properly under SteamOS.
Note: SteamOS wipes your hard drive during installation. Be careful.