When it comes to the R500 series 3D support, it has been in place for almost one year. In late February of 2008 they publicly released R500 3D programming documentation (along with an R300 3D register guide and updated GPU microcode) and less than a month they had the first signs of success: glxgears was running. About two months after having hardware-accelerated gears, there was 3D success with Compiz now running on the R500 Mesa implementation. It was even possible to play a few games with the open-source R500 driver. Since that point the R500 OpenGL support in Mesa has continued to improve.
What is lost by switching to the open-source stack for the R500 hardware? Well, the open-source ATI stack still is not on a level playing field when it comes 3D performance. The open-source stack can actually outperform the Catalyst driver when it comes to 2D acceleration with its EXA support and X Render extension support (see our R700 2D Performance comparison and Catalyst vs. X.Org Radeon Driver 2D Performance). The xf86-video-ati and xf86-video-radeonhd drivers are the X.Org DDX drivers that are compatible with the R500 series. The R500 support in the RadeonHD driver is hard-coded while the other driver has its support provided by AtomBIOS.
The 3D performance will improve once switching to the Gallium3D architecture along, using LLVM to optimize GPU shaders, switching to GEM / TTM for kernel memory management, and all of the optimizations that come about due to recent improvements in the X.Org stack. To illustrate where the R500 performance is at right now, we have enclosed some new benchmarks on the following pages.
Beyond the quantitative performance, the Catalyst Linux driver offers more aggressive power management through PowerPlay than what is available in the open-source drivers. The open-source drivers are RandR 1.2 compatible (now RandR 1.3 when using X Server 1.6), but -- at this time -- there is no feature-rich GUI available.
Gained from switching to the open-source stack is a better "out of the box" experience as when installing a recent desktop Linux distribution you will get the latest X.Org and Mesa bits, which does include 2D, 3D, and X-Video acceleration up through the R500 series. A continual stream of innovation can also be found within the open-source stack. Additionally, there is no fear of losing support from the open-source drivers any time soon. The xf86-video-ati driver currently has mode-setting support for the R100 through RV770 GPUs in a single driver. Red Hat is even working on adding kernel mode-setting support to the older ATI GPUs. There are still open-source drivers around for the 3Dfx Voodoo graphics cards (and even older cards still) that will receive an occasional update of fixes and compatibility for the latest X Server.
When a new X Server release is out, there is also no wait for driver support like there usually is with the Catalyst driver. Additionally, many open innovations and specifications are first supported in open-source drivers (that is no surprise there). The open-source ATI stack first supported RandR 1.2 and GLX_EXT_texture_from_pixmap for Compiz support long before either feature was found in the Catalyst suite for Linux.