The Most Comprehensive AMD Radeon Linux Graphics Comparison
Radeon HD 6870: This Sapphire beauty with the Barts XT is running at 900MHz with a 1050MHz clock for its 1024MB of memory. These newer parts support the "UVD3" engine for video decoding, which is still crippled in this latest revision. This generation of GPUs supports OpenGL 4.1, but it will be years before we see OpenGL 4.1 in the open-source world. Even when that arrives, it will be in crippled form due to the aforementioned patent / IP problems, unless there happens to be major patent reform in the near future or some sort of IP covenants granted to Mesa.
Radeon HD 6950: The Radeon HD 6950 is the only Cayman GPU being tested (the HD 6950 is a Cayman Pro). This Sapphire model is speeding at 800MHz and 1250MHz for its 2GB of GDDR5 video memory.