In this paper we put forward a design for a multicomputer system based on a network of workstations which we call COMA-BC. It has a common address space in which a shared variables prograanming model can be used. The management of the shared address space is performed in a similar way to that in existing multiprocessor COMA systems. To be exact, the shared address space is divided into blocks, and their copies reside in the attraction memories of the workstations. The key piece in this system is the coherence cache protocol that we have developed. The goal of the protocol is to minimize the number and size of the messages travelling through the network so that the parallel applications can be executed without creating inconsistencies in the different copies of the blocks residing in the dif- ferent nodes of the system. The proposed system has not been built, but a simulation environment has been specifically developed. This environment allows the simulation of the execution of parallel standard applications in COMA-BC. This sim- ulation environment is driven by execution. Using the results and a simple analytic model, results have been obtained concerning the performance of the execution of standard parallel applications in terms of accelera- tion and efficiency. These results show the viability of a COMA-BC system as a way of exploiting parallelism at a low cost using workstations.
