An Argument for Simple COMA

Ashley Saulsbury, Tim Wilkinson, John B. Carter, and Anders Landin
Swedish Institute of Computer Science
Box 1263, S-164 28 Kista, Sweden


We present design details and some initial performance results of a novel scalable shared memory multiprocessor architecture. This architecture features the automatic data migration and replication capabilities of cache-only memory architecture (COMA) machines, without the accompanying hardware complexity. A software layer manages cache space allocation at a page-granularity - similarly to distributed virtual shared memory (DVSM) systems, leaving simpler hardware to maintain shared memory coherence at a cache line granularity.

By reducing the hardware complexity, the machine cost and development time are reduced. We call the resulting hybrid hardware and software multiprocessor architecture Simple COMA. Preliminary results indicate that the performance of Simple COMA is comparable to that of more complex contemporary all-hardware designs.

Full paper appeared in Future Generation Computing Systems Journal, 1995.