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The MOSI protocol is an extension of the basic MSI cache coherency protocol. It adds the O wned state, which indicates that the current processor owns this block, and will service requests from other processors for the block.
Modified Owned Exclusive Shared Invalid (MOESI) is a full cache coherency protocol that encompasses all of the possible states commonly used in other protocols. In addition to the four common MESI protocol states, there is a fifth "Owned" state representing data that is both modified and shared. This avoids the need to write modified data back ...
Protocol MOESI type – Data stored in M (D) or in O (SD) and the other caches in S (V) – Data is sent to the requesting cache from the "owner" M (D) or O (SD). The requesting cache is set S (V) while M (D) is changed in O (SD). – The MM is not updated. Protocols MESI type and MEI – Data stored in M (D) and the other caches in S (V) state
The MESI protocol adds an "Exclusive" state to reduce the traffic caused by writes of blocks that only exist in one cache. The MOSI protocol adds an "Owned" state to reduce the traffic caused by write-backs of blocks that are read by other caches. The MOESI protocol does both of these things.
This method ensures that only one copy of a datum can be exclusively read and written by a processor. All the other copies in other caches are invalidated. This is the most commonly used snooping protocol. MSI, MESI, MOSI, MOESI, and MESIF protocols belong to this category.
Mosi or MOSI may refer to: Mosi (given name) Mosi (surname) Molybdenum silicide (MoSi 2), an important material in the semiconductor industry; MOSI protocol, an extension of the basic MSI cache coherency protocol; MOSI, Master Out Slave In (data output from master), Serial Peripheral Interface pin and logic signal
However, scalability is one shortcoming of broadcast protocols. Various models and protocols have been devised for maintaining coherence, such as MSI, MESI (aka Illinois), MOSI, MOESI, MERSI, MESIF, write-once, Synapse, Berkeley, Firefly and Dragon protocol. [2] In 2011, ARM Ltd proposed the AMBA 4 ACE [12] for handling coherency in SoCs.
The MESIF protocol is a cache coherency and memory coherence protocol developed by Intel for cache coherent non-uniform memory architectures. [1] The protocol consists of five states, Modified (M), Exclusive (E), Shared (S), Invalid (I) and Forward (F). [2] The M, E, S and I states are the same as in the MESI protocol. The F state is a ...