A data processing system includes a processor core and a cache memory hierarchy coupled to the processor core. The cache memory hierarchy includes at least one upper level cache and a lowest level cache. A memory controller is coupled to the lowest level cache and to a system memory and includes a physical write queue from which the memory controller writes data to the system memory. The memory controller initiates accesses to the lowest level cache to place into the physical write queue selected cachelines having spatial locality with data present in the physical write queue.