Phoronix: LLVMpipe: OpenGL With Gallium3D on Your CPU
The software rasterizer used in Mesa that allows for software acceleration of OpenGL on the CPU without any assistance from the graphics processor has largely been useless. Even with a modern-day, multi-core processor, the performance of Mesa's software rasterizer has been abysmal. The performance of Mesa classic DRI drivers have traditionally been poor anyways compared to the high-performance, proprietary NVIDIA/ATI graphics drivers, but when dealing with just the software rasterizer there really aren't any games or applications that run well. Fortunately, software acceleration on Gallium3D is very much a different story thanks to LLVM.
What I think is most interesting with these benchmark results is that the r300g driver seems to be A LOT faster than just a month ago. Check the graph for Open Arena in this article. Its about twice as fast with the same graphics card while the classic driver shows the same numbers. And as you can see in this new article the numbers are not at all cpu limited, so the weaker cpu in the older test should not be a factor.
Simple question: Good enough to run KDE 4.4 desktop effects with it on a Phenom 9950 X4 (not OC'd)?
probably, but the simpler XRender based composition mode may be more suitable for software rendering.
Are you planning to run a headless machine with a vnc server or something? Otherwise anything that has a DVI port is capable of faster compositing.. they stopped selling those framebuffer-on-a-stick-devices 20 years ago.
Don't forget: with GPU acceleration, you can have cool 3D-effects AND run an application, too!