AMD Releases R300 3D Register Guide @ Phoronix
 

Last month right before FOSDEM 2008, the 3D programming documentation for the R500 GPUs (Radeon X1000) series was released. This documentation consisted of a register reference guide for the R500 GPUs as well as a programming guide covering such areas as the command processor, vertex shaders, and fragment shaders. While the register reference guide for the R600 series is still being worked on, for those with older ATI graphics processors, AMD has went back and created a register reference guide for the R300 series.