Cache-Only Memory Architecture (COMA)

Figure 4.5: COMA shared memory system.

• Similar to the NUMA, each processor has part of the shared memory in the COMA (see Fig. 4.5).
• However, in this case the shared memory consists of cache memory. A COMA system requires that data be migrated to the processor requesting it.
• There is no memory hierarchy and the address space is made of all the caches.
• There is a cache directory (D) that helps in remote cache access.
• The Kendall Square Research's KSR-1 machine is an example of such architecture.