Coherence protocol

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In computer science, a coherence protocol is a protocol which maintains the consistency between all the caches in a system of distributed shared memory; the protocol maintains memory coherence according to a specified consistency model.

Examples of such protocols are the MESI protocol, MSI protocol, MOSI protocol (more generally: the MOESI protocol), home-based coherence protocols, and many others. Most of the cache protocols in multiprocessors are supporting sequential consistency model, while in software distributed shared memory more popular are models supporting release consistency or weak consistency.