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AMD RadeonSI Graphics Driver Still Troublesome On Linux
Due to the aforementioned problem of id Tech 4 games failing to work with RadeonSI on newer kernels, for the Doom 3 run we only have the results of Catalyst against Linux 3.8 with Mesa 9.3-devel. The Radeon HD 7850 graphics card was at just 5% the speed of the Catalyst driver while the HD 7950 was 12% the speed of the binary driver.
With Nexuiz we see a huge improvement in the open-source Radeon driver performance when upgrading from Linux 3.8 to Linux 3.11 due to improvements in between there for the Radeon DRM like tiling support. The kernel upgrade led to the frame-rate being up by five times for Nexuiz. With the kernel upgrade, the Radeon HD 7850 was running at 51% the speed of Catalyst on Ubuntu 13.04 while the Radeon HD 7950 was at 48%. Interestingly, enabling DPM on Linux 3.12 Git only boosted the HD 7850 performance by a few frames per second; as mentioned already, the HD 7950 failed to work with Radeon DPM.
The kernel upgrade helped the RadeonSI Gallium3D performance a lot for OpenArena too. Radeon DPM on the HD 7850 continued to have little impact on the overall performance. For OpenArena 0.8.8 at 1920 x 1080, the HD 7850 was performing at 21% the speed of Catalyst while the HD 7950 was only at 18%.