1. A cache index for indicating whether an input address is contained in a data array of a cache memory system, wherein said data array comprises a plurality of elements, said cache index comprising: a plurality of data sets, each data set corresponding to an element of said data array; a first set of said plurality of data sets having a first tag and a first state; said first tag comprising a first plurality of bits indicating the identity of a first cache line stored in a first element of said plurality of elements of said data array; and said first state comprising a first state indicator indicating a number of cache lines which are mapped into said first set, wherein each of said cache lines corresponds to an element of said data array.