The block is also written to memory, and other caches pick the data off the bus and update their copies (if any).

The block is also written to memory, and other caches pick the data off the bus and update their copies (if any). If no other cache has a copy of the block, the block is loaded from memory in state dirty. In update protocols in general, since all writes appear on the bus, write serialization, write-completion detection, and write atomicity are simple. [5.4] What cache line size is performs best? Which protocol is best to use?