https://bugs.freedesktop.org/show_bug.cgi?id=50655
--- Comment #12 from Alex Deucher agd5f@yahoo.com 2012-06-07 07:16:57 PDT --- I think I know what's going on here. There's a hw bug on r6xx where you need to re-emit a CB register if some state further up the pipeline changes even if the CB state has not changed. I remember fixing it in r600c, but I can't find the commit...