What is MSI in computer architecture?

In computing, the MSI protocol – a basic cache-coherence protocol – operates in multiprocessor systems. As with other cache coherency protocols, the letters of the protocol name identify the possible states in which a cache line can be.

What is cache coherence and MESI protocol?

The MESI protocol is an Invalidate-based cache coherence protocol, and is one of the most common protocols that support write-back caches. There is always a dirty state present in write back caches that indicates that the data in the cache is different from that in main memory.

Where is MESI protocol used?

The MESI protocol is widely used in multiprocessor de-signs, for example, in the Futurebus+ interconnection bus. The MPC601 uses this protocol.

What are the objectives of MESI protocol?

The MESI protocol is a method to maintain the coherence of the cache memory content in hierarchical memory systems [2], [3]. It is based on four possible states of the cache blocks: Modified, Exclusive, Shared and Invalid.

What are MSI devices?

MSI. MSI (first defined in PCI 2.2) permits a device to allocate 1, 2, 4, 8, 16 or 32 interrupts. The device is programmed with an address to write to (generally a control register in an interrupt controller), and a 16-bit data word to identify it.

What is snoopy bus protocol?

Snoopy Bus Protocols Snoopy protocols achieve data consistency between the cache memory and the shared memory through a bus-based memory system. Processor P1 writes X1 in its cache memory using write-invalidate protocol. So, all other copies are invalidated via the bus. It is denoted by ‘I’ (Figure-b).

What is directory protocol?

Directory Access Protocol (DAP) is a computer networking standard promulgated by ITU-T and ISO in 1988 for accessing an X. 500 directory service.

What is MSI logic circuits?

The term medium scale integrated circuit (MSI) logic refers to a set of basic combinational logic circuits that implement simple, commonly used functions such as decoders, encoders, multiplexers, and demultiplexers. MSI logic can also include operations such as comparators and simple arithmetic circuits.

What is MSI decoder?

A decoder is a combinational circuit that converts binary information from the n coded inputs to a maximum of 2n unique outputs. If the n-bits coded information has unused bit combinations , the decoder may have less than 2n outputs.

What are the different states of a block in MSI?

In MSI, each block contained inside a cache can have one of three possible states: Modified: The block has been modified in the cache. The data in the cache is then inconsistent with the backing store (e.g. memory). A cache with a block in the “M” state has the responsibility to write the block to the backing store when it is evicted.

What do the letters in the MSI protocol names mean?

As with other cache coherency protocols, the letters of the protocol name identify the possible states in which a cache line can be. In MSI, each block contained inside a cache can have one of three possible states:

What are the states of a cache in MSI?

In MSI, each block contained inside a cache can have one of three possible states: M odified: The block has been modified in the cache. The data in the cache is then inconsistent with the backing store (e.g. memory ). A cache with a block in the “M” state has the responsibility to write the block to the backing store when it is evicted.

What is the difference between modified and shared in MSI?

In MSI, each block contained inside a cache can have one of three possible states: Modified: The block has been modified in the cache. The data in the cache is then inconsistent with the backing store (e.g. memory). Shared: This block is unmodified and exists in read-only state in at least one cache.