The Xonotic performance was not vastly impacted but the Radeon HD 5830 and Radeon HD 6870 graphics cards do appear to regress with this yet-to-be-merged patch for some OpenGL workloads.
It looks like there's still some work to be done in optimizing the flushed depth texture handling, which can yield some performance improvements as shown in the Lightsmark data, but that there's some setbacks elsewhere from this work.
For benchmarks of other recent AMD graphics cards and to find out how a tweaked open-source driver can better perform against Catalyst on Linux, see this month's An Optimized Open-Source Driver Tries To Compete With AMD Catalyst article.
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