440 EVOLUTION OF COMPUTER BUILDING BLOCKS
A companion paper to the chapter on Cm* discusses the programming issues raised by a computer module structure [Jones et at., 1978]. An operating system, called "Star OS," manages a single Cm* cluster. It provides capability addressing, memory allocation, software module declaration, process management, message transmission, processor multiplexing, and trap and interrupt handling. Star OS is distributed in such a fashion that any kernel function can be executed in any CM. To decrease average memory reference time, 8 Kbytes of what the designers believe to be the most frequently executed Star OS software (interrupt handling, process switching, and message communication) is duplicated in each CM.
Since the time that the article was written, construction of a 50 computer modules Cm* has begun and is planned to be operational by the end of 1978 for evaluation in 1979. The extension of Cm* is known as "Cm*/50" and is described in Chapter 16. It will be used to test ideas on parallel processing methods, fault tolerance, modularity, and the extendability of the Cm* structure.
The four design methods presented in this part are compared in Table 2. As stated in Chapter 2, the predominant design level in the future will be the PMS level, using fifth generation components (microcomputers) as building blocks. The challenge to designers and researchers is therefore to understand what communication structures are needed to interconnect these building blocks.