MESI and MOESI protocols
- Modified (M) – Cache line has been modified. It is different from main memory, and is the only cached copy.
- Owned (O) – Cache line is dirty and is possibly in more than one cache. A cache line in the Owned state holds the most recent, correct copy of the data. Only one core can hold the data in the Owned state. Other cores can hold the data in the Shared state.
- Exclusive (E) – Cache line is the same as main memory and is the only cached copy.
- Shared (S) – Same as main memory but copies might exist in other caches.
- Invalid (I) – Line data is not valid as in simple cache