occam for multi-processor DEC alphas

A multi-processor implementation of occam2.1 for interconnected DEC Alpha processors has been derived from the Kent Retargetable occam Compiler. Each Alpha processor is supported over a PCI bus by a T425 transputer, whose links complete the communications fabric. This paper reports on the software mechanisms for supporting these platforms from occam so that they appear just like any transputer system - a collection of processing nodes connected by channels placed on links. Advantage was taken of a proprietary multi-threading kernel, supplied as part of 3L Parallel C/AXP, to support parallel inter-node communication. occam multiprocessing is supported by the KRoC kernel running within one of the 3L threads. The performance of generated code and networked systems has been benchmarked, with particular care being taken to measure tile interaction overheads between the Alpha and its communication fabric. An image analysis program was also used in the benchmarking as an example of a real multi-processor application.