Computer Physics Communications 26 (1982) 277—283 277 North-Holland Publishing Company FIFTH GENERATION COMPUTERS Philip C. TRELEAVEN and Isabel GOUVEJA LIMA Computing Laboratory, University of Newcastle upon Tyne, Newcastle upon Tyne, NE] 7RU England Fifth generation computers are analogous to LEGO building blocks, with each block corresponding to a microcomputer and a group of blocks working together as a computer system. These computers will represent a unification of currently separate areas of research into parallel processing and into VLSI processors. Parallel processing based on data driven and demand driven computer organisations are under investigation in well over thirty laboratories in the United States, Japan and Europe. Basically, in data driven (e.g. data flow) computers the availability of operands triggers the execution of the operation to be performed on them; whereas in demand driven (e.g. reduction) computers the requirement for a result triggers the operation that will generate the value. VLSI processors exploit very large scale integration and the new simplified chip design methodology pioneered in US universities by Mead and Conway, allowing users to design their own chips. These novel VLSI processors are implementable by simple replicated cells and use extensive pipelining and multiprocessing to achieve a high performance. Examples range from a powerful image processing device configured from identical special-purpose chips, to a large parallel computer built from replicated general-purpose microcomputers. This paper outlines these topics contributing to fifth generation computers, and speculates on their effect on computing. I. Introduction Illiac IV [3] to support the continuing demand from computational science for computers with The Japanese are predicting J 1] that the next higher performance; and (iii) the inability of these (the fifth) generation of computers, available in high-speed computers to utilise advances in tech- the 1990’s, will not be based on the traditional nology such as very large scale integration (VLSI). sequential control flow computer organisation. Three largely separate areas of research are They see this major change in computing as an currently trying to solve these problems. The first opportunity for them to dominate the computer area concerns the growing interest in new classes market and are investing over $400M in research of programming language in which parallelism and into these future computers. serialism are both implicitly specified. The most All previous generations of computers have been well-developed class of these very high level lan- based on the so-called von Neumann organisation guages is functional languages, which we will dis- (a single computer incorporating processor, com- tinguish as single assignment languages and ap- munications and memory; linear organisation of plicative languages. In single assignment languages fixed size memory cells; low level machine lan- (e.g. VAL [4—6], ID [7], LUCID [8]) an identifier guage; sequential execution of instructions). This may only be assigned to at one point in the organisation is very good for sequential comput- program. In applicative languages (e.g. LISP [9], ing. However, computing is moving from a centra- SASL [10,11], FP [12]) program transformations lised, sequential world to a decentralised, parallel are simply the result of applying functions to their world, arguments. The second area of research concerns Symptomatic of the current problems of com- the design of parallel computer architectures which puting in general are those of computational sci- utilise the inherent parallelism in computations. ence. Namely: (i) the lack of a “naturally parallel” Examples of these parallel architectures are data high level language in which to program highly flow computers [13,14], in which the availability of parallel computations; (ii) the inability of conven- operands triggers the execution of the operations tional high-speed computers like Cray 1 [2] and to be performed on them, and reduction corn- 001 0-4655/82/0000—0000/$02.75 © 1982 North-Holland