A DSM architecture for a parallel computer Cenju-4

A parallel computer Cenju-4 is a cache-coherent non-uniform memory access (ccNUMA) multiprocessor and designed to be scalable up to 1024 nodes. For scalability, Cenju-4 adopts a bit-pattern directory. This scheme enables more precise representation than other imprecise schemes, such as a coarse vector scheme. Cenju-4 utilizes multicast and gathering functions of the network for delivering invalidation request messages and for collecting replies. This enables store access latency to be scalable, even when the block is shared among all nodes. Cenju-4 also prevents starvation and deadlock by queuing certain types of messages in the main memory. This enables a full solution to the starvation problem with centralized directory scheme, and to the deadlock problem with one physical or virtual network. The buffer sizes required for queuing messages at each node are only 32K bytes and two 64K bytes on a 2024-node system. In this paper, we present the design of the DSM architecture and some performance results.