Shared-memory architecture

In computer architecture, shared memory architecture (SMA) refers to a multiprocessing design where several processors access globally shared memory.

Shared memory architectures may use:

• Uniform Memory Access (UMA): all the processors share the physical memory uniformly.

• Non-Uniform Memory Access (NUMA): memory access time depends on the memory location relative to a processor.

• Cache-only memory architecture (COMA): the local memories for the processors at a node is used as cache.

In a SMA system processors communicate by reading and writing memory locations. The two key problems in scaling an SMA system are:

• performance degradation due to "contention" when several processors try to access the same memory location.

• lack of "coherence" if memory is cached and goes out of synch with the original values as modifications take place.

See also

• Shared memory

References

Computer architecture