Shared memory in transputer systems

Although the use of shared memory goes against the ethos of the Occam model of computation, there are cases which justify its use in transputer systems. The author presents three such cases which arose within the ParSiFal Alvey project at Manchester University. Each has its own justification for the use of shared memory and uses it in a different way. In the first instance it was used as the vehicle for communication at an acceptable speed between a SUN system providing access to filestore and user console I/O. Secondly the bandwidth limitations of transputer links was overcome in the development of a card to allow real-time animation on a high resolution screen connected via links to a transputer network. Finally, advantage was taken of the clustering of transputers in the ParSiFal T-rack to provide alternative, higher speed, communication channels between transputers in a cluster by providing shared memory to which they all have access. Special care was exercised to allow the preservation of strict synchronisation between the communicating processes