Abstract: A memory management arrangement includes a memory management unit, a cache memory and a queue arrangement. The queue is a first-in, first-out (FIFO) buffer which can queue failed memory access requests and return them as inputs to the memory management unit via the bus 5 for retrying through the memory management unit at a later time. If a memory access request sent to the memory management unit experiences a cache “miss”, instead of blocking memory access requests until the required address data has been loaded into the cache, the memory management unit operates to place the failed memory access request in the replay queue, and allows subsequent memory access requests to continue. The failed memory access requests in the queue are then continuously circulated through the memory management unit from the queue alternately with new memory access requests from other access initiators.