- the amd gpu conception (contrary to nvidia) need that the kernel take time to analyze the command buffer, for security reason. fglrx do not do that.
- there is some limitation is the API, and it's not easy to fix. Moreover the kernel api is freeze, contrary to nouveau.
- r600g have a design that is not the best to do what it do.
To conclude, in fact, the main "problem" with r600g is in the kernel, not really in gallium side.