Cache Coherence for Multi Processing
In computing, cache coherence (also cache coherency) refers to the consistency of data stored in local caches of a shared resource. Cache coherence is a special case of memory coherence. When clients in a system maintain caches of a common memory resource, problems may arise with inconsistent data.
This is particularly true of CPUs in a multiprocessing system. Referring to the "Multiple Caches of Shared Resource" figure, if the top client has a copy of a memory block from a previous read and the bottom client changes that memory block, the top client could be left with an invalid cache of memory without any notification of the change. Cache coherence is intended to manage such conflicts and maintain consistency between cache and memory.