CHANGEABILTY OF CACHE IN PROCESSING VARIOUS DIFFERENT ADRESSING ERRORS

A cache memory subsystem has multilevel directory memory and buffer memory pipeline stages shared by at least a pair of independently operated central processing units and a first in first out (FIFO) device which connects to a system bus of a tightly coupled data processing system. The cache subsystem includes a number of programmable control circuits which are connected to receive signals representative of the type of operations performable by the cache subsystem. These signals are logically combined for generating an output signal indicating whether or not the contents of the directory memory should be flushed when any one of a number of types of address or system faults has been detected in order to maintain cache coherency.