The ATI Stream SDK v2.2 currently defaults to exposing 50% of the physical GPU memory to OpenCL™ applications. Certain developers may require accessing additional physical memory in order to optimize their applications when running on the GPU.
For developers who wish to experiment with increasing the amount of physical memory that is accessible to their OpenCL™ applications, the default 50% setting can be changed by setting the environment variable GPU_MAX_HEAP_SIZE to the percentage of total GPU memory that should be exposed.
For example, if you wanted to set the exposed GPU physical memory size to 75%, you need to the GPU_MAX_HEAP_SIZE environment variable to 75.
GPU_MAX_HEAP_SIZE must be set to an integer value between 0 and 100, inclusive.