1. An apparatus comprising: a system memory that is accessible via a system bus; and a graphics processing unit (GPU) comprising: a local memory; a memory copy engine operable to retrieve first data from the system memory via the system bus and store the first data into the local memory, and retrieve second data from the local memory and store the second data into the system memory via the system bus; and a shader processor operable to retrieve the first data from the local memory, process the first data to generate the second data, and store the second data into the local memory.