A memory controller includes a host interface for receiving memory access requests including access addresses, a memory interface for providing memory accesses to a memory system, and an address decoder coupled to the host interface for programmably mapping the access addresses to selected ones of a plurality of regions. The address decoder is programmable to map the access addresses to a first region having a non-power-of-two size using a primary decoder and a secondary decoder each having power-of-two sizes, and providing a first region mapping signal in response. A command queue stores the memory access requests and region mapping signals. An arbiter picks the memory access requests from the command queue based on a plurality of criteria, which are evaluated based in part on the region mapping signals, and provides corresponding memory accesses to the memory interface in response.