Radeon Gallium3D Can Beat AMD's Catalyst In Select Workloads
All benchmarking of the Ubuntu Radeon graphics performance happened via the open-source Phoronix Test Suite software.
The system hardware/software details...
When starting things off with id's idTech4-powered Doom 3, the performance of the Catalyst driver from five years ago is still very much faster than the open-source Radeon Linux graphics driver from today. The Catalyst driver still has nearly a 2x advantage over the open-source driver to be found in Ubuntu 13.04. The open-source graphics driver support has certainly matured (it wouldn't even run Doom 3 in Ubuntu 10.04) and made faster in some of the succeeding Ubuntu Linux releases, but still no match to Catalyst. There were also similar differences with the Doom 3 performance when testing at a lower resolution too.
The open-source Radeon graphics driver for the X1800XT graphics card has been made faster in the past few years, but it's still no match to the Catalyst performance. With Ubuntu 13.04 on Mesa 9.0, the performance is up to 84% the speed of Catalyst on the same hardware, but with Mesa 9.1 it falls back to 50% the speed of Catalyst. This is due to Mesa 9.1 finally implementing proper multi-sample anti-aliasing (MSAA) for the R300 Gallium3D driver. Catalyst was using MSAA too, but it's just faster than R300g.