I'm seeing a problem in Ubuntu 12.04 and later. When I boot into a video game like Half Life 2, I get massive lag (FPS drops) and my CPU runs at 100%. My system even lags for games like SuperTuxCart but it has great performance on the desktop, playing videos in 1080p etc.
When I go into "Big Picture" mode (a feature that allows me to play my games on my TV) on Steam, it loads in the lowest possible resolution and when I try to change it, Steam warns me that my display device only has 268 MB of dedicated GPU Memory. My system is a HP Pavilion 2248-G6 with an AMD A4-4300M graphics card, running catalyst 13.11 beta drivers.