A CACHE CONTROL CIRCUIT HAVING A PSEUDO RANDOM ADDRESS GENERATOR

A data processing system incorporating a cache memory 2 and a central processing unit. A storage control circuit 10 is responsive to a programmable partition setting PartVal to partition the cache memory between instruction words and data words in dependence upon whether the central processing unit 4 indicates with signal I/D whether the word to be stored within the cache memory 2 resulted from an instruction word cache miss or data word cache miss. The cache memory array 2 may have a programmably sized portion locked down so that it is not replaced. The selection within the complementary programmable range where overwriting takes place uses a pseudo random selection technique using pseudo random number generator in the form of a linear feedback shift register triggering incrementing of a counter.