1. A computer processing system comprising: a hierarchical memory system having at least one cache; and a processor having execution logic that generates memory requests that are supplied to the hierarchical memory system; wherein the at least one cache stores a plurality of cache lines as well as a plurality of valid bits for each cache line, wherein each cache line includes a plurality of data bytes, and wherein the plurality of valid bits for a given cache line correspond to the plurality of data bytes of the given cache line and provide an indication of the validity of the corresponding data bytes of the given cache line.