What happens if a processor attempts to read or write to a cache line in the 'I' (Invalid) state?
The Invalid (I) state means the data in that cache line is stale and cannot be trusted. Therefore, any read or write request to a block in the 'I' state must be treated as a Cache Miss. This forces the cache to issue a request onto the system bus to fetch the correct, up-to-date data from the lowest level of memory (main memory) or from another cache that holds a Modified ('M') or Exclusive ('E') copy.
