What are the protocols used in the cache coherence system?

In general there are two schemes for cache coherence; a snooping protocol and a directory-based protocol. The snooping protocol only works with a bus-based system, and uses a number of states to determine whether or not it needs to update cache entries, and whether it has control over writing to the block.

What is cache coherence and cache coherence protocols?

In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. Cache coherence is intended to manage such conflicts by maintaining a coherent view of the data values in multiple caches.

What are the four states in MESI model and what are their roles?

The MESI protocol makes it possible to maintain the coherence in cached systems. It is based on the four states that a block in the cache memory can have. These four states are the abbreviations for MESI: modified, exclusive, shared and invalid.

What is the full form of Mesi protocol?

The MESI protocol is a formal mechanism for controlling cache coherency using snooping techniques. Its acronym stands for modified, exclusive, shared, invalid and refers to the states that cached data can take. Transition between the states is controlled by memory accesses and bus snooping activity.

What are the different types of cache coherence?

The two most common types of coherence that are typically studied are Snooping and Directory-based. Each has its own benefits and drawbacks. Snooping protocols tend to be faster, if enough bandwidth is available, since all transactions are a request/response seen by all processors.