Phoronix checks out open-source drivers, you can check it out over here.
The open-source graphics driver landscape is ever changing
with new work going into Mesa / Gallium3D near daily. While many
improvements have been made in recent time, the open-source drivers have
a ways to go in competing with the proprietary competition. Even the
open-source AMD driver, which is developed using documentation from AMD
as well as code and engineering resources within the company, it has a
tough time competing with the well-optimized Catalyst driver.
Fortunately, the AMD driver is now largely centered on the two Gallium3D
drivers: R300g and R600g, and have pushed away their classic Mesa DRI
drivers into maintenance mode. The R300g supports the R300 through R500
ASICs (up through the Radeon X1000 series) while the R600g driver
supports all ATI/AMD hardware past that point up through the latest
Radeon HD 6000 series and Fusion. In this article, we are seeing where
the performance is currently at for the classic Mesa, Gallium3D, and
Catalyst drivers under Linux."