Simple COMA Shared Memory and the RS/6000 SP

Simple COMA is a method for sharing address spaces among different nodes of a distributed memory computer. This method provides high performance without the complex and costly changes required by other shared memory organizations. It also retains the positive attributes of a distributed memory multicomputer, such as scalability and high availability. This paper explains the Simple COMA shared memory architecture and the potential implementation of this architecture on the IBM RS/6000 SP parallel computer. Background v1.2.8 scoma.doc 1 1 Background The IBM RS/6000 Scalable POWERparallel Systems (SP) is a distributed memory system comprised of separate, full function nodes. Each node's memory is addressable only from the processor(s) in that node. Each node is controlled by a separate kernel, and message passing is used for communication between nodes. On current SP systems, parallel programs which share data between multiple nodes do so explicitly via one of the various message pa..