1. A computer cache memory organization called Probabilistic Set Associative Cache (PAC) physically organized as a direct mapped cache but employs a cache tag search policy of a set-associative cache, in which N−1 extra tag bits in the cache directory entries are employed in addition to the direct mapped cache tag in order to implement N-way associative cache behavior and a replacement algorithm which implements two different replacement algorithms in one, namely the direct mapped and the N-way set associative replacement algorithms.