MOESI is a cache coherency protocol- like the MESI (Modified, Exclusive, Shared and Invalid) but with an "Owned" state. Modified: Data is recent (and has been modified!) and this data is held by no other processor or the memory. This data is 'dirty'. Exclusive: Data is recent and present only in the current cache and the memory holds a copy as well. No other processor holds this data. Shared: Other caches may also have this data and the data matches memory. This data is 'clean'. Invalid: The data is invalid or incorrect. Owned: The Owned state signifies that the data is Modified as well as Shared. While the data must be still written to memory, this can be delayed since there is no need to write the modified data into memory before sharing it.