In a multi-core system using the MESI protocol, Core A has a cache line in the 'Exclusive' state. Core B suddenly attempts a 'Read' operation on that same memory address. What is the final state of the cache line in Core A, and what action is triggered?
In MESI, the 'Exclusive' state means Core A has the only cached copy, and it is "clean" (matches memory). When Core B wants to read it, the line is no longer exclusive to one core. Both cores will now hold the line in the Shared state. Since the data in Core A was clean, Core B can simply read the data from Main Memory (or Core A can supply it to speed up the bus, but the state transition to Shared is the key architectural requirement).
