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jihyel

the MESI protocol is named after the four states of a cache line: modified, exclusive, shared and invalid. In modified state, the data in the cache line is modified, and the copy in main memory is not up to date. In exclusive state, the data in the cache line is unmodified, but is guaranteed to reside in the cache. In shared state, the data is unmodified, and there may be copies of the data in other caches. In invalid state, the cache line does not contain valid data.