I currently have openCL 1.0 but need to update it to 1.1 for it work fully with Blender. As far as I can tell, Snow Leopard does not support 1.1, but Lion does. I haven't been able to fully confirm this though--it seems information on OpenCL on Mac OS is very hard to find. One post I found said that 1.1 was included in the 10.7 SDK. Is this true?