Book reviews

Analysing models of multiprocessor system performance M Ajmone Marsan, G Balgo and G Conte

Performance models of multi- processor systems MIT Press, Cambridge, /vIA, USA (1986) £34.95 pp 294

Multiprocessor systems are becoming increasingly important as single- processor systems using existing technology and traditional archi- tectures reach their limit in speed of operation. I therefore approached this book with particular interest.

The book is concerned with quantifying the performance of multiprocessor architectures analy- tically, that is, through mathematical equations rather than through simulation or construction. Simulation and construction would often follow an analytical study. The analytical study presented is aimed at computer designers and researchers (though this is not stated specifically) and I would think a very strong mathematical background would be a distinct advantage. To give the flavour of the book, chapter two, the first main chapter after a brief introduction, has 129 numbered equations, chapter three has 72 numbered equations and there are 366 numbered equations in all. The mathematics involves Markov processes, queueing theory and stochastic Petri nets.

There are three authors but no noticeable change of style between chapters. The style is readable though somewhat concise. The material is a distillation of published research results and is not a teaching text in any way; there are few numerical examples distributed in the text and there are no end-of-chapter problems. It is clear, though, that the authors have an extensive knowledge of mathematical modelling and the large number of references are incorporated into the text extremely well.

The book is divided into two parts. The first presents the mathematical theory of Markov processes, queueing theory and Petri nets in three chapters (about 90 pages). This material requires careful reading to assimilate and would be unsuitable as a first introduction to the subject. Indeed some of the steps from one equation to the next are not immediately obvious; some equations are preceded by phrases such as 'we finally obtain', 'which reduces to' or 'after a little manipulation become'. Only a couple of numerical examples are given and these help comprehension tremendously. There was no treatment of bus contention analysis using standard probability theory. Perhaps this was seen as inappropriate for an advanced text.

The second part is concerned with applying the theory of the first to specific multiprocessor architectures. The architectures include shared bus systems, multiple bus systems and crossbar switch systems. A good number of Markov models and performance curves are given. Assumptions have to be made for specific architectures and models to achieve a closed solution. Often the arbitration algorithm is assumed to be first-come first-served. Fixed priority, rotating priority or least recently used (LRU) algorithms did not seem to receive specific treatment. The final chapter briefly reviews other aspects of performance evaluation such as task synchronization and the construction of a system to obtain performance results.

As the authors point out, there are few books concentrating on analytical performance models as this one does and thus the book makes a real contribution to the literature helping those involved in research of multiprocessor performance models. The book could perhaps be used as an advanced postgraduate text. The quality of printing is excellent with no discernible errors. Priced at £34.95, however, the book is somewhat expensive.

Barry Wilkinson Brighton Polytechnic, UK

RISC overview relieves shortage of information D Tabak RISC architectu~ Research Studies P~ss, Letchworth, UK (1987)£19.95 pp 175

An overview of the RISC approach, stressing its advantages and disadvantages, and giving examples of research prototypes and of commercial products, this book is aimed at engineers in the computer industry and students on advanced courses in computer science or electrical engineering.

It is largely successful in communicating the ideas behind the RISC approach. A reader with a reasonable understanding of

computer architecture, but no previous exposure to RISC designs, should obtain a good understanding of the principles from the book. The RISC concept is not closely definable, but the principles are elucidated by explaining the rationale behind the approach and by offering examples.

The section on the advantages and disadvantages of the RISC approach introduces a number of the arguments for and against, but wisely leaves the conclusion for posterity.

The descriptions of various example RISC systems are rather shallow in their analysis, and some of the details are inaccurate. This does not seriously detract from the

usefulness of these examples both as introductions to the individual designs and as illustrations of the RISC approach.

The attempt made in the book to define the RISC approach, to say which processors do or do not meet the RISC criteria, is to my mind unimportant. The RISC approach is a mental attitude in the designer rather than an architectural feature in the processor. No architect of a new processor can ignore the work that has been done in this area. He/she may choose to follow the conventional route and build a complex instruction set, but must have a strong argument to support this choice, such as code

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