AMD is not supported by SteamOS for now, but here is a to check what happens when you run SteamOS with an AMD graphics card. The card used in the test is AMD Radeon HD 6950. SteamOS booted up quite normally with the AMD card, and operating system ran smoothly without any lags. However when checking the system specification, SteamOS displayed 0.0 video memory, though it recognized AMD Redeon HD 6950 under the video card.
via N4G: pc news feed http://n4g.com/news/1418466/steamos-amd-gpu-test-system-boots-smoothly-and-recognizes-the-gpu-but-shows-no-video-memory
via N4G: pc news feed http://n4g.com/news/1418466/steamos-amd-gpu-test-system-boots-smoothly-and-recognizes-the-gpu-but-shows-no-video-memory