Abstract: A data processor has a cache memory with an associative memory for storing at least a first and second groups of associations between a respective main memory addresses and cache memory locations. At least one cache memory location is dynamically assignable to different ones of the groups for use in associations of the assigned group. When an instruction indicates a main memory address a group is selected group for finding the cache memory location associated with the main memory address. In an embodiment, the processor accesses streams of addresses from iteratively computed main memory addresses. Each stream has its own group of associations of addresses from the stream with cache memory locations assigned to that group. The remaining cache memory locations are accessed with set associative mapping. Thus, cache memory locations can be assigned to different streams on an “as needed” basis and the remaining cache memory locations can be used for non-stream addresses.