Cache coherency

Cache coherency (alternatively cache coherence or cache consistency) is the property that accessing a cache gives the same value as the underlying data, even when the data was modified by a different process after the caching was performed. This is important for consistent operation of multiprocessor systems in which each CPU has a non-shared cache of a shared memory area. Various protocols have been devised for maintaining cache coherency, such as the MESI protocol[?] and the MOESI protocol[?].