Architecture
MESI Protocol
A cache coherence protocol tracking line states as Modified, Exclusive, Shared, or Invalid.
Detailed Explanation
MESI ensures all processors see consistent memory despite private caches. Modified means the cache has the only valid copy (dirty). Exclusive means clean but only copy. Shared means clean and potentially in other caches. Invalid means not present or stale.
State transitions occur on local operations (reads, writes) and snooped bus transactions. For example, writing to a Shared line requires invalidating other copies and transitioning to Modified.