The "valid" state means that the cache line is current.
This ensures that the three lookups stay within a cache line.
The cache line may be changed to the Modified state at any time in order to modify the data.
A cache line in the shared state holds the most recent, correct copy of the data.
Shared cache lines may not respond to a snoop request with data.
A cache line in the invalid state does not hold a valid copy of the data.
A store buffer is used when writing to an invalid cache line.
A 64-bit data bus allowed the cache line to be transferred in a 4-cycle burst.
Both caches are direct-mapped and have a 4-byte cache line.
If the starting offset within the cache line is zero, all of these modes reduce to the same order.