Catalyst 11.6 is a really strange release.
I have 6950 equipped with 2GB of RAM. Up until 11.6 CL_DEVICE_GLOBAL_MEM_SIZE was always 1GB which is one half of available RAM. But now with 11.6 the global memory size for the device is 838860800 bytes, that is 800MB. CL_DEVICE_MAX_MEM_ALLOC_SIZE is reduces in the same degree.
I understand that AMD is free to change these values as far as they fit into OpenCL requirements. But I wonder why is only 39% of RAM available to OpenCL buffers?