Synchronizing processors through memory requests in a tightly coupled multiprocessor

To satisfy the growing need for computing power, a high degree of parallelism will be necessary in future supercomputers. Up to the late 70s, supercomputers were either multiprocessors (SIMD-MIMD) or pipelined monoprocessors. Current commercial products combine these two levels of parallelism.

Effective performance will depend on the spectrum of algorithms which is actually run in parallel. In a previous paper [Je86], we have presented the DSPA processor, a pipeline processor which is actually performant on a very large family of loops.

In this paper, we present the GREEDY network, a new interconnection network (IN) for tightly coupled multiprocessors (TCMs). Then we propose an original and cost effective hardware synchronization mechanism. When DSPA processors are connected with a shared memory through a GREEDY network and synchronized by our synchronization mechanism, a very high parallelism may be achieved at execution time on a very large spectrum of loops including loops where independency of the successive iterations cannot be checked at compile time as e.g. loop 1: