Open-Source RadeonSI Gallium3D vs. AMD Catalyst On Linux
Starting with Nexuiz, we see the RadeonSI-based graphics cards have much greater performance to make up for than the R600-based graphics cards. The Radeon HD 6950 graphics card was running more than 50% the speed of the Catalyst driver while the Radeon HD 7850 was at about 14% the speed of Catalyst and the Radeon HD 7960 was about 26% the speed.
The very basic OpenArena 0.8.5 game also shows how far behind the RadeonSI Gallium3D driver presently is compared to the previous generations of AMD GPUs using the R600g driver. For this hardly demanding GPU test, the Cayman HD 6950 was at 74% the speed of the Catalyst Linux driver while the HD 7850 and HD 7950 were at 11% and 18%, respectively.
With the GLSL-using OpenArena 0.8.8, the Radeon HD 7000 series graphics cards fall to less than 10% the speed of Catalyst. Beyond the bad performance relative to the HD 6000 series in this "out of the box" Fedora Linux testing, the RadeonSI driver is presently limited to OpenGL 2.1 compliance while the R600 driver is at OpenGL 3.1 and the Catalyst driver fully supports OpenGL 4.2 on the hardware as intended.