Hardware Developments

By 1978 it had become evident that the hardware of the Monads I system was not adequate to support the software ideas which had been developed, in particular the idea of a persistent virtual memory in which all major software resources (comparable to files in conventional systems) ­ and including data files ­ should reside as information hiding modules and which were to be directly addressable from persistent processes, protected by capabilities. Consequently a further hardware development, known as Monads II, was undertaken by another research student, David Abramson. This was based on a further HP 2100A computer but the hardware changes were much more radical. This included the first implementation of the orthogonal model for combining paging and segmentation, and the first implementation of capability registers containing large virtual addresses.

The Monads II hardware was from the beginning regarded as a prototype, in particular with respect to the sizes of virtual addresses, and a plan was formulated to build a further hardware system, Monads III, which would have full 60 bit virtual addresses. However, this plan was abandoned when Prof. Keedy accepted the Chair in Operating Systems at Darmstadt in Germany in 1982. Shortly before this another student, John Thomson, had started to work on a Ph.D. in association with an operating system for the Monads II/III systems. His work continued to a successful completion at Monash, despite the difficulties of having a supervisor in Germany.