Microprogrammable Computer Architectures

References

1 'Recent developments in digital logic design'. Proceedings of conference at School of Electrical Engineering, University of Bath, UK, Sept. 1977 2 LECHNER, R.J.: 'Harmonic analysis of switching functions', in MUKHOPADHYAY, A. (Ed.): 'Recent developments in switching theory' (Academic Press, New York, 1971) 3 KARPOVSKY, M.G.: 'Finite orthogonal series in the design of digital devices' (John Wiley, N.Y., 1976) 4 EDWARDS, C.R.: 'The application of the Rademacher-Walsh transform to Boolean function classification and threshold-logic synthesis', IEEE Trans., 1975, C-24, pp. 48-62 5 HURST, S.L.: "The application of Chow parameters and Rademacher-Walsh matrices in the synthesis of binary functions', Comput. J., 1973,16, pp. 165-173

6 EDWARDS, C.R.: 'Matrix methods in combinational logic design'. Ph.D. thesis, University of Bath, 1973 7 DERTOUZOS, M.L.: "Threshold logic: a synthesis approach'. Research Monograph 32, MIT Press, 1965 8 HURST, S.L.: 'Testing logic networks', Wireless World, 1977, 83, pp. 82-86 9 WALLIS, J.S.: 'Hadamard matrices', (Springer-Verlag, Lecture notes 292 N.Y., 1972) 10 GOLOMB, S.B.: 'On the classification of Boolean functions', IRE Trans., 1959, CT6, special supplement, pp. 176-186 11 EDWARDS, C.R.: "The design of easily tested circuits using mapping and spectral techniques', Radio & Electron. Engin., 1977, 47, pp. 321-342

The metatheory asks where, in the world of informationprocessing concepts, does one find tools which are applicable to computing? The theory of finite-state machines is The theory of computer science rapidly (but thoroughly) dismissed, since, through its finite J.M. Brady nature, it does not apply to even simple computations such Chapman & Hall, 1977, 250pp., £750 (paperback £395), as multiplication. Turing-machine concepts get around the ISBN 0 412 12930 3 problem of finiteness by assuming the existence of an infinite tape on which symbols may be written and from When the word 'theory' is mentioned in polite conversation, which they may be read. Much centres on Turing's thesis many (including computer engineers and scientists) either that 'processes which could naturally be called algorithms shrink away, feeling insecure in their lack of knowledge of are precisely those which can be carried out on Turing mathematics, or ask whether it is of immediate use. If not machines'. the latter, they feel justified in shrinking away for ever. Since 'computability' must be central to the sought-after I take the opposite view, and side with Mike Brady, who theory, the author goes on to seek a way of expressing at the outset of his book firmly states that '. . . theory inthis as programming effort related to Turing machines, creases our understanding of, and systematises our knowlleading to the concept of the general recursive functions of edge about, the subject domain'. He goes on to say that Hilbert and Kleene, which provide a formalism that supports significant practical advances are possible in the case of a Turing's thesis. theory of computer science. This added bonus is important The nature of the 'computability' discussion in Part I is since it often stops people from wasting their time on unsuch that it deals essentially with seemingly negative results, attainable projects. that is, 'what can't be computed?' In contrast, Part II starts Brady's book is the first of which I know that, in terms with the list-processing type of formalism developed by that most can understand, discusses both the nature of the McCarthy and approaches positive results. These range over limitations and concepts inherent in a science of comquestions of problem solving, the nature of programming puting (a metatheory) and the extent to which we have languages, data structures, and program termination. travelled towards the development and application of a The book is compellingly written, and its paperback theory in itself. version should be welcomed by students and teachers of After setting out the philosophical and practical obcomputer science and electronic information systems as an jectives in a compact and clear way in the first chapter, the enlightening and stimulating text. The hardened programmer rest of the book is divided into two parts corresponding to might also find it mind-broadening reading. the metatheoretical and theoretical aims mentioned in the paragraph above. I. ALEKSANDER

Book reviews

Microprogrammable computer architectures

Alan B. Salisbury

North-Holland, 1976, 162 + xiipp., US $17-95/Dfl. 4500, ISBN 0 444 00175 1 This short book provides an introduction to the architecture of computers designed to support microprogramming by the user, in contrast to computers with read-only control memories that have been designed to implement a particular machine language. By architecture is meant those aspects of the structure that are seen by the user. The first three chapters provide a historical overview of the subject and develop a comprehensive framework for the analysis of the architecture of various machines. Matters touched on are whether the format of a microinstruction is fixed or variable, how many fields it contains, and the degree to which the information in them is coded, together with various aspects of microinstruction sequencing. I might remark in passing that the section on horizontal and vertical 48

microinstructions confirms me in my view that this terminology has now become so confused as to be no longer useful. The remaining two-thirds of the book deal with particular machines. There are chapters on the Microdata 3200, the Interdata 8/32, the Burroughs B1700, and the Nanodata QM-1; a final chapter deals more briefly with the Control Data 5600, the Digital Scientific META4, the HP2100/ 21 MX, the Varian 73, the Intel 3000, and the Western Digital MCP 1600. There is much material packed into these chapters, which are illustrated with tables and diagrams taken in many instances from the manufacturers' manuals. Some readers will perhaps find the accompanying text rather too condensed. Nevertheless, the book is to be welcomed for the amount of information that it brings together. M.V.WILKES

COMPUTERS AND DIGITAL TECHNIQUES, MA Y 1978, Vol. 1, No. 2