I am trying to use the PERSISTENT_MEM flag for buffer creation with a 7970 GPU. However, it appears to be behaving more like ALLOC_HOST_PTR, i.e. it seems to be transferring data from host to device for every NDRangeKernel call. clinfo shows that the driver version supports virtual memory, but it does not indicate the presence of the 'cl_amd_device_persistent_memory' extension. Is there something extra I have to do to enable that extension, other than installing the 13.1 version driver? I have attached my clinfo output in case that helps.