D^m-l-
(
!" , i r \ k * m - 1 - (m - l)/(* + 1)
also reached by Schneiderman and Goodman (in the context
of their study) by using a different approach.
= (m - 1) kj{k + 1)
Acknowledgement
The author acknowledges that Professor P. M. Stocker set the
problem to him as an exercise and that Dr. W. F. Burton
assisted him in developing the formula.
(A: + \)m
Q.E.D.
(6) reveals that a batch size of k queries causes approximately
the first k/(k + 1) cylinders of the file to be travelled; a result
References
CARDENAS, A. F. (1975). Analysis and performance of inverted data base structures, CACM, Vol. 18, No. 5, pp. 253-263.
PEZARRO, M. T. (1976). A note on estimating hit ratios for direct-access storage devices, The Computer Journal, Vol. 19, No. 3, pp. 271-272.
SCHNEIDERMAN, B. and GOODMAN, V. (1976). Batched searching of sequential and tree structured files, ACM Transactions on Database
Systems, Vol. 1, No. 3, pp. 268-275.
TEOREY, T. J., and PINKERTON, T. B. (1972). A comparative analysis of disc scheduling policies, CACM,
WATERS, S. J. (1975). Estimating magnetic disc seeks, The Computer Journal, Vol. 18, No. 1, pp. 12-19.
Vol. 15, No. 3, pp. 177-184.
Computer Architecture, second edition, by C. C. Foster, 1977;
300 pages, (van Nostrand Reinhold, £10-65)
The first edition of this book was published about seven years ago.
The changes in content are almost all additions and this edition
is some 75 pages longer than the original. All the logic diagrams
have been redrawn using contemporary symbols and many of the
other diagrams have been improved. The number of diagrams
and their accuracy and clarity is a very attractive feature of the
book.
Like the original this book is based on a course in computer
architecture given at the University of Massachusetts, it is a teaching
text covering a wide range of topics, some of necessity in a rather
shallow manner. The vast majority of people considering reading,
and possibly buying, this book will not have seen the original.
This review therefore will consider the total contents rather than
concentrating on the changes.
The first chapter covers number representation, the second gates
and elementary logic and the third storage mechanisms. These
80 pages give an easy to read coverage of the topics but the treatment in parts is perhaps a little too shallow. A more serious criticism
of the chapter on storage mechanisms is the unevenness of the coverage in relation to the importance of the different mechanisms in the
building of present day computers. For example whilst six pages on
magnetic bubbles is reasonable for this type of book one page on
magnetic recording as compared with two on parametrons and two
on fluidic devices is not. There is also little attempt to compare
the advantages and disadvantages of the different storage techniques
which is important when considering the design of any computer
system.
Chapter four is mainly concerned with the organisation of bits of
memory into storage systems; here again my criticism is on the
balance of coverage. Almost half of the chapter is on implementing
push down stacks with other store arrangements getting about
one page each.
How should computer architecture be taught? I am sure that
there are many detailed answers to this question but two general
approaches seem to exist. Do you describe the functional features
of parts of several real systems and attempt to identify the underlying
principles? Or do you invent a design which illustrates the functions
you wish to describe? The latter method has the advantages of a
coherent design, if you do it properly, but can suffer from a lack
of practical detail. Dr Foster chooses to use as the vehicle for the
second part of his book a synthetic design of a simple 16 bit parallel
computer with a primitive instruction set based on a 12 bit address
and a four bit function. This design is explained in detail in chapter
five and in later chapters, as more sophisticated aspects of computer
architecture are introduced, the design is extended to include
some of these features. This approach gives a theme to the descripVolume 21 Number 2
tion of the various architectural features which would otherwise
have been difficult to achieve. Occasionally the reader may be confused between what is a description of a real machine and what is
purely a paper design. On the whole the approach is successful
in this book and the descriptions of more complex instruction
formats, store organisation and input/output systems which occupy
chapters six and seven are linked by reference to extensions to
the design proposed in chapter five. Also in chapter eight where
there is a short description of microprogramming this is well
illustrated by giving a microprogrammed version of the same
simple machine.
An expected addition to the first edition is the chapter on microcomputers. This is quite short but is sufficient to introduce the basic
ideas which are illustrated by descriptions of features of three
different microprocessors, the AMI-9209, the Intel 8080 and the
Signetics 2650.
Chapters ten, eleven and twelve, which occupy the last 60 pages
of the book, are devoted to large computers. It is in this part that
I feel that the author has failed to present an accurate picture.
There has been some revision since the first edition but several parts
have been retained which could profitably have been replaced.
For example, devoting nine pages to the same paper design as in
the first edition and having less than one page on the ILLIAC IV,
one page on multiple function units and three pages on pipelining
presents a false picture of the design features which have led to the
high speed of today's super computers. Incidently even though
ILLIAC IV has been somewhat slow to develop it is a little unkind
to retain, from the first edition, the phrase 'when the ILLIAC IV
comes on the air'.
The whole of this section suffers from being a mixture of paper
designs and sketchy descriptions of real systems which it would be
impossible for the uninformed reader to distinguish. These 60 pages
could have been better used to describe the different approaches
to attaining high speed which have been tried together with some
discussion of their relative success and how the design of future
systems will be influenced by advances in technology.
The first nine chapters of the book are well organised and clearly
written; they would provide a good support text for a general course
on computer architecture, particularly in a degree programme which
otherwise concentrated on the software and application aspects
of computer science.
Each chapter has sufficient references (except the chapter on logic
which has none!). There could, however, have been more updating
of these references from the first edition.
Throughout the text there are short questions which if answered
in detail would certainly help the reader to get a thorough understanding of the material covered.
F. H.
SUMNER
(Manchester)
133
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Book review