While this week we published benchmarks that showed how NVIDIA's Linux driver can compete with Windows 8 -- when using the closed-source drivers and not the open-source Nouveau solution -- and that even the FreeBSD NVIDIA performance is competitive, this isn't the case for AMD's drivers. From the same Core i7 Haswell system as used for the NVIDIA testing, AMD Radeon graphics cards were tested on Windows 8 and Linux. It wasn't a surprise that the open-source Radeon Gallium3D was much slower than Catalyst, but took us off guard a bit was that the Linux Catalyst driver does take some noticeable performance hits over the Microsoft Windows driver in some OpenGL workloads.
The modern Linux Catalyst driver shares mostly common code with the Windows Catalyst driver aside from the platform-specific bits and other obvious differences. Our past testing of the AMD drivers between Windows and Linux has been mixed with the performance some years being closer than in other years where the AMD Linux driver has fallen behind. In terms then of the Radeon Gallium3D driver alternative that Linux users have for an open-source driver, it's not a big surprise that it falls short of the highly-tuned Catalyst driver backed by dozens (or even hundreds) of developers and is a much larger code-base.
This AMD Linux vs. Windows testing is happening in the same fashion as our NVIDIA GeForce testing earlier in the week. All tests occurred on an Intel Core i7 4770K "Haswell" system with a 240GB OCZ Vertex 3, Intel DH87RL motherboard, 16GB of RAM, and a selection of graphics cards. The GPUs tested this time were a Radeon HD 6770, Radeon HD 6870, and Radeon HD 7850 graphics card.
Ubuntu 13.10 was the base operating system but with the Xfce 4.10 desktop environment. The Radeon Gallium3D tests happened from Mesa 9.2.0-devel Git at the time of testing, LLVM 3.3, swap buffers wait disabled for the xf86-video-ati DDX, and the Linux 3.11 Git kernel with DPM enabled. The Catalyst Linux testing was done from the Linux 3.9 kernel (for binary driver compatibility) with fglrx 13.15.3 / OpenGL 4.3.12414. The Windows testing was done via Microsoft Windows 8 Pro x64 with the Catalyst 13.6 Beta and all available operating system updates at the time of testing.
All benchmarking on Windows and Linux and between the Radeon Gallium3D and Catalyst drivers was handled in a fully automated and reproducible way using a spectrum of OpenGL benchmarks and games via OpenBenchmarking.org and the Phoronix Test Suite.