What’s the difference between memory coherence and consistency?

In memory hierarchical, it needs to be coherence and consistency. However, they are different things. What are the differences?

Memory coherence: a memory system is coherent if any read of a data item returns the most recently written value of that data item (what values can be returned by a read).

Memory consistency: A memory consistency model for a shared address space specifies constraints on the order in which memory operations must appear to be performed (i.e. to become visible to the processors) with respect to one another.(when a written value will be returned/seen by a read).

Coherence defines the behavior of reads and writes to the same memory location, while consistency defines the behavior of reads and writes with respect to accesses to other locations.

Answered by harryxiyou.

Weiwei Jia

Weiwei Jia is a Ph.D. student in the Department of Computer Science at New Jersey Institute of Technology since 2016. His research interests are include storage systems, operating systems and computer systems.

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