Requires having latest El Capitan beta 3 OSX due to ome crucial fixes made in the compiler. Supports same features as NVidia OpenCL apart from CMJ (there's no experimental feature set support in megakernel yet). Uses megakernel internally, which works much better than the split kernel. Split kernel is not supported on OSX still, needs to be investigated still. Some more details can be found there: http://wiki.blender.org/index.php/Dev:2.6/Source/Render/Cycles/OpenCL#AMD_on_OSX