Cache
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State Description
Invalid A cache line in the invalid state does not hold a valid copy of the data. Valid copies of the data can be either in main memory or another processor cache.
Exclusive A cache line in the exclusive state holds the most recent, correct copy of the data. The copy in main memory is also the most recent, correct copy of the data. No other processor holds a copy of the data.
Shared A cache line in the shared state holds the most recent, correct copy of the data. Other processors in the system may hold copies of the data in the shared state, as well. If no other processor holds it in the owned state, then the copy in main memory is also the most recent.
Modified A cache line in the modified state holds the most recent, correct copy of the data. The copy in main memory is stale (incorrect), and no other processor holds a copy.
Owned A cache line in the owned state holds the most recent, correct copy of the data. The owned state is similar to the shared state in that other processors can hold a copy of the most recent, correct data. Unlike the shared state, however, the copy in main memory can be stale (incorrect). Only one processor can hold the data in the owned state—all other processors must hold the data in the shared state.
tag index block offset
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  • L1 cache
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