The Cost Effective Application of Computer
Graphics in an industrial Research Environment
In One Volume
KEITH EDWARD CLARKE, B. Tech, D.I.C., C.Eng, M.I.E.E
Thesis Submitted For The Degree of M. Phil of the University of London.
Research carried out at
The Post Office Research Department Dollis Hill London.
In conjunction with
The Department of Computing and Control
IMPERIAL COLLEGE of SCIENCE and TECHNOLOGY.
Under the Industrial Research Laboratories collaboration scheme.
February 1975.
Supervisor: W.S. ELLIOTT, M A, FIEE, F. Inst. P, FBCS
Professor of Computing. TABLE OF CCNTENTS
List of Appendices
Acknowledgements
Declaration
Disclaimer
Summary
Abbreviations
1 INTRODUCTION
1.1 Motivation for the Work 1.2 Objectives of the Thesis 1.3 Computer Graphics - State of the Art at the Start of the Project 1.4 Computing in the PO Research Department 1.5 The Identification cf Suitable Applications
USER ATTITUDES
2.1 Concern for Data Security 2.2 Trade Union Interests 2.3 WorkingOutside Nornal Hours 2.L Failure of Computer Teams to Meet Promised Dates 2.5 A Reluctance to Discuss Mistakes 2.6 Hostility to Changing Computer Systems 2.7 The "Trojan Horse" Effect 2.8 A Lack of Confidence when Discussing Computers 2.9 Over Confidence in Computing
3 THE SURVEY OF POTENTIAL APPLICATIONS 3.1 The Design of Printed. Circuit Boards 3.2 Errors uccuring in PCB Design by Manual Methods 3.3 Integrated Circuit Design 3.4 Integrated Circuits - Assessment of Reliability 3.5 Graph Plotting and Curve Fitting 3.6 PERT '3.7 Machine Shop Scheduling 3.8 Programming of Numerically Controlled Machine Tools 3.9 Accommodation Plans 3.10 Flow Charts and Coding for Stored Program Control Telephone Exchanges 3.11 Computer Assisted Drafting 3.12 Cn-line Production o -P Spectrograms 3.13 Legibility of Alphanumeric Characters 3.14 Decision Networks 3.15 Models of Transistors 3.16 Thin Film Technology Circuits 3.17 Text Editing
2 L SUMMARY OF THE EQ'SIPIYLN T AVAILABLE 4.1 Storage Tube Terminals 4.2 Refreshed Displays 4.3 Storage Tubes with Local Computers 4.4 Television 11,,-pe Displays 14.5 Automatic Dra..wing Systems 4.6 Other Developments
5 THE DERIVATION OF A STRATEGY 6 NON-TECHNICAL FACTORS IN THE CHOICE OF INDUSTRIAL EQUIPMENT
7 WORK WITH STORAGE TUBE TERMINALS
7.1 Selecting the Terminal 7.2 Choice of Communications Link 7.3 Software for Graph Plotting 7.4 The objectives of CUPID Summarised 7.5 The Design Philosophy of CUPID 7.6 The CUPID Log 7.7 Details of the CUPID Implementation 7.8 CUPID Facilities 7.9 User Reaction to the Hardware 7.10 User Reaction to the CUPID Software 7.11 Case Histories involving the use of CUPID 7.12 The Cost of Using CUPID 7.13 An Analysis of the CUPID Command Usage
FULLY INTERACTIVE aRAPHICS
8.1 The Display Hardware 8.2 Assessing the PerforAlance of Problem Solving Systems 8.3 original Calclations on the Cost of PC3 Design 8.4 Evaluation of the PCB and Design Automation after 1 Year
9 RECENT DEVELOPMENTSN COMPUTER GRAPHICS
10 PROGRESS UN APPLICATIONS OTHER THAN PCBs, ICs AND GRAPH PLOTTING
11 CONCLUSIONS
REFERENCES
3 LIST OF APPENDICES
A A log of CUPID Usage and the CUPID Command Index
B The Syntax of the CUPID Command Language
C Hardware Configuration of the Refreshed Graphics Computer
D Software Purchased for IC and PCB Design
E Bench—mark Results for PCB Design. Drawing Office Comments
NOTE ON THE ILLUSTRATIONS
Most illustrations in this thesis have been copied directly from hard copy units. They are thus an exact replica of the screen information with respect to size and content but have suffered a little in line qu ality. Also, it has not proved possible to follow British Standard BS 4811 on the orientation of graphs in every case. ACKNOWLEDGE=TS
The Industrial Laboratories Collaboration Scheme offers immense intellectual
opportunities at the price of some administrative difficulties. The full co-operation of Professor William Elliott, my college tutor, and Mr
W. E. Thomson, my industrial tutor, is acknowledged with thanks.
The support and active encouragement of line managers in the PO Research
Department was also crucial. This was forthcoming from Mr W Bray (Director)
Dr Tillman (Deputy Director), Mr S Fedida (Head of Division) and Mr J A Treece.
All successful industrial projects are team efforts and this work is no exception. Messrs Wbods, Babbs, and Silvester made special
contributions noted in the declaration of originality. Almost every group in Research Department was contacted at some stage for information, and this
was readily given. Of these the integrated circuit design group under the
control of Messrs W D Morton and E Jackets was troubled on more occasions
•than most. Other information was obtained from Telecommunications Development
Department (TD9.4), Telecommunications Management Services Division (TMS2.3)
and from Mr J Forrest of the Research Department CAD group. The author is
grateful to all his PO colleagues for this cooperation in providing information.
The computer program named CUPID is mentioned frequently in the thesis
although it is not included per se. Mr B J Wood's speedy and error free
implementation of this program contributed substantially to the success of that part of the project. DECLARATION
The work described in this thesis is the original work of the author, with the following exceptions. The detailed design of the CUPID command language (appendix A) was the work of Mr B J Woods, while working under the direction of the author.
The PCB design bench-mark tests (appendix E) were performed by Mr T Babbs, leading draughtsman, working under the direction of the author.
Parts of appendix D (a summary of the PCB and IC design programs)
are based on a document prepared by Mr R Silvester, when working under the dir-
ection of the author.
With two short exceptions, none of the material has been previously used
or published by the author. Two paragraphs of section 8 were used in a paper read by the author at the 1972 BCS conference on Computer
Performance (47). An abbreviated account of the initial stages of the Storage tube project, Section 7, was given in a paper published jointly
with Mr Woods at Datafair 1973 (48) INDUSTRIAL RESEARCH LABORATORIES JOINT COLLABORATION SCHEME.
DISCLAIMER
The opinions expressed in this thesis are those of the author and do not necessarily reflect the policies of the British Post Office.
7 SUMMARY
This thesis is concerned with the economic and practical problems that arise when computer graphics are applied in an organisation primarily concerned with electronics research. It includes an account of a comprehensive survey of possible applications in the Post Office Research Department, from which it
'4vasconcluded that of the many possible applications, graph plotting, curve fitting, PCB design, and IC design were likely to prove most profitable. Other applications were considered to have potential but were gtven a lower priority. This survey also revealed that human attitudes were likely to be as important as technical problems in the success of the work and these are discussed fully.
Direct view storage tube terminals were used for the graph plotting and
curve fitting. The choice of the equipment provided and the software
written is described. Particular attention is paid to a program called
CUPID because it is thought that the techniques used, namely an interpretive
graphical command processor under the control of a time sharing operating
system, represent a useful advance in the field. Also, CUPID maintains a log of command usage which is now available for a period of
18 months use. An analysis of this log is included for the benefit of
others implementing similar programs. A DCF calculation for this part of the project is included from which it is concluded that curve fitting
and graph plotting are likely to be profitable for any organisation
producing at least 2 complex graphs per working day.
It was decided to purchase both hardware and software for the PCB and IC
applications and details of the selection process are given. An account is
given of the reaction of both groups of designers to the facilities provided. . In the case of PCB production, detailed bench-marks were carried out and the data were used in DCF calculations. These indicate that the design of PCBs
by computer graphics is likely to cost less than by manual methods provided that at least 2 boards with 150 connections are designed
per working day.
The major conclusions are as follows.
1 Computer graphics cost less but only the largest organisations
(by UK standards) will be able to justify the purchase of their own
equipment. Bureau use is a useful alternative for a smaller organisation.
2 Human factors are as important as technical ones in this field.
3 The dominance of software costs in the DCFs is noted.
The crucial importance of high speed hard copy facilities is confirmed.
A concluding section discusses recent developments in the
state of the art against the background of these conclusions. KEY TO ABBREVIATIONS.
IC Integrated Circuit.
CUPID Conversational Utility Program for Information Display.
DCP Discounted Cash Flow
DO Drawing Office.
DILIC Dual In Line Integrated Circuits.
PO (British) Post Office.
ATE Automatic Test Equipment.
DVST Direct View Storage Tube.
CRT Cathode Ray Tube.
EDP Electronic Data Processing
10 THE COST EFFECTIVE APPLICATION OF COMPUTER GRAPHICS IN AN INDUSTRIAL
RESEARCH ENVIRONMENT.
1 INTRODUCTION
1.1 Motivation for the Work
To ensure that a potentially profitable technique, namely computer
graphics, which had been developed in the Universities was applied
effectively in a cost-conscious industrial environment.
1.2 Objectives of the Thesis
To document the success and failures of that application, and the
practical problems encountered.
To draw from the case histories studied some general conclusions
on the industrial applications of computer graphics to electronic
design.
To document certain advances in computer programming techniques achieved
in the course of the investigation.
To study in particular the savings and costs involved in the applica-
tion of computer graphics.
1.3 Computer Graphics - The State Of The Art At The Start Of The Work
When this project started in 1971 those engaged in computer graphics
had solved the major technical problems associated with the visual (1) display of computer generated information. Sutherland had
demonstrated the techniques of producing pictures by using computer
output to control the X and Y amplifiers of a cathode ray tube, and
of using a photo cell and associated circuitry (referred to as a "light
11 pen") to draw and manipulate the components of that picture. Two and three dimensional representations could be created and rotated. (2) L G Roberts had solved the problem of removing "hidden" lines in
3-dimensional representations. On the software side, data structuring techniques had evolved to facilitate the modelling and representation of the information to be displayed. A debate on the possible hardware configurations continued, see for example Myer and Sutherland(6) and this was seen as an important problem of optimisation.
The work described above had concentrated on the use of the "refreshed"(45) cathode ray tube. About this time the direct view storage tube(9) was first marketed as a computer terminal. Based on techniques derived from tubes originally developed for radar and television picture storage and from the storage scan converter it offered static pictures at a much lower price than the refreshed tubes. Apart from a Review Paper by
Van Dam(8) the storage tube and its associated software had not been the subject of many published papers.
Despite the above technical progress the number of industrial
.applications was not large. Men absorb about 90% of their information visually, and diagrams, sketches and pictures are widely used for the storage of their thoughts and for communication to others. Thus computer graphics could be expected to play a prime part in man/ computer communications. For refreshed graphics the main difficulty was the cost of the hardware that had to be dedicated to a designer for his exclusive use during a design session. This had fallen from around £200,000 (for say, an Elliott 4130 display) in the mid 60s to between £120,000 (for say, an IBM 2250) and £70,000 (for say, a PDP 15) by 1970. Expense of this order could only be justified in special circumstances. These occurred in the aerospace and
12 ship-building industries where the cost of the end product is so large
that a small percentage saving in product costs pays for the expensive
design tools involved. In the automobile industry large scale mass
production achieves a similar effect. Other applications such as the
design of glass bottles and fashion shoes were effective but too
specialised to bring about widespread industrial use. In the electronics
industry computer research effort had concentrated on programs for the (11,19) (10) design of integrated circuit masks and printed circuit boards
In the former case technology was changing rapidly and the trend
towards large scale integration had given an incentive to CAD work,
although the benefits were difficult to cost rigorously. The economics
of computer graphics for PCBs were the subject of considerable debate.
For simple boards conventional draw ing and tape methods were competitive
and for multi-layer boards (ie more than two layers) fully automatic
routing by the computer was practicable.
Other work, eg Neill(39), had concentrated on interactive circuit design
but was not then widely used in industry. This is probably because
of the lack of suitable analogue device models at frequencies then
being investigated. Also, the programs were regarded by many
engineers as difficult to use.
Despite the titles of some of the papers, neither of the most relevant
conferences (Computer Aided Design, Southampton, April 1969 and
Computer Graphics 70 at Brunel University) had produced much evidence
•of cost effectiveness, an exception being the aerospace work at (58) Lockheed-Georgia described by Chasen . Practicing electrical
engineers, eg Trier(13) , tended to reserve their judgement.
13 Against this background it was decided to investigate the application
of computer graphics in the Post Office Research Department.
1.4 Computing in the Post Office Research Department
The function of the Department is to conduct scientific and engineering
research for both the Telecommunications and the Postal Businesses of
the British Post Office. In accordance with the trend in most
industrial laboratories projects are related to business objectives
by a system of financial sponsorship by operational departments.
About 1800 people work for the Department of which about 1000 are
professional staff. The majority of these are electronic engineers
but physicists, chemists, mathematicians and other .professions are
also represented. Much experimental work is carried out and many
of the experiments produce large volumes of data. A services section,
employing )400 people, provides comprehensive facilities for the
production of mechanical and electrical prototypes. Component
reliability is of major importance to the British Post Office and
. this has justified the creation of facilities for manufacturing and
testing integrated circuits.
Computers are used extensively but their use is rigorously costed.
Proposals for the use of computer graphics had, in general, to be
justified in financial terms.
At the start of this project use was being made of computers in
both batch and time sharing modes. A twin processor Burroughs
B5500 provided a time sharing service for 30 simultaneous users drawn
from a user population of about 100. A further 50 users made use
of three commercial time sharing bureaux. Obsolescent Elliott 803
and 503 computers were used for batch processing.
4 Plans for the acquisition of a new large computer to replace the above assortment were well advanced, and an IBM 370/168, with an extensive communications network, was purchased during the period of the project. Algol was the recommended language for all PO research workers but the use of BASIC (by time sharing users) and of Fortran was increasing. PL/1 was introduced with the 370/168.
The fact that data files existed for so many computers, and programs existed in so many languages, was to prove an important consideration in the application of graphics.
Graph plotting facilities for the general user were provided by an off-line plotter. A Ferranti flat bed precision plotter was used to cut integrated circuit masks and was programmed using a B5500 version of the Camp system(33) Free time was available on this plotter which was capable of wider application.
The use of graphical output varied widely from group to group. A group concerned with semiconductor research had used
plotters to produce stereo pairs of semiconductor doping profiles
Silvester & Brown,(28)) while other groups used only tabulated output.
If any conclusions relevant to industry in general are to be drawn from
experiences gained in one establishment it is important to compare
the situation prevailing at the start of this project with that
in other British research establishments. It is difficult to find
any documented surveys on the subject but the author believes from
his experiencethile employed by the Computer Advisory Service of the
(then) Ministry of Technology that this situation was typical of
most general industrial and Government research laboratories.
5 The Post Office had been early to recognise the value of time-sharing and this had produced a slightly greater emphasis on interactive techniques than was usual at the time.
Thus, computer graphics were being introduced to a user population that was accustomed to slightly better than average input/output facilities. 1.5 The Identification of Suitable Applications
It was apparent from a variety of published papers ( eg(10211119)) that the design and manufacture of printed and integrated circuits was a potentially profitable area but the details of the potential work load in the laboratories had not been studied. In order to investigate these applications more thoroughlyand to identify other applications,questions on graphics were included in a survey of computer users that was carried out by the computer group. This survey revealed 20 users interested in computer graphics. Each user was then visited for a discussion of his problems. Two important lessons were learnt during the course of these investigations. The first was the value of extensive personal contact with the ultimate users of the proposed system. By meeting the user one could get full details of his existing computing practices. The items to be probed would include the computer, operating system and languages used, the nature and extent of existing data files, and the degree of security required for the data files. One also obtained other information less easy to document but equally valuable. The attitude of the user (and his colleagues, staff and supervisors) to the use of computers became apparent during the discussions. A feel for
the nature of the work carried out by the group was also valuable
and often samples of the end product or demonstrations of the
processes involved were forthcoming. 16 The second lesson learned was that it had been a mistake, potentially
serious but soon rectified, to send the survey only to existing
computer users. It had been thought that as computer graphics
were an advanced computing technique, existing computer users were
the logical people to involve at the start of a project. Instead,
the facilities that computer graphics offer proved attractive
to many non computer users. (Printed circuit board design is a notable
example). Thus the circulation of a questionnaire to all staff above
a certain level would have been more appropriate, and was eventually
carried out.
2 USER ATTITUDES
During the discussions with users much information was gained on the
attitude of the users to computers. It must be emphasised that the object of recording these attitudes is not to imply criticism of those holding them. In many cases they are indicative only of prudence on
behalf of those concerned, and result from past failures of the computing
profession. The intention is to comment on a hitherto neglected area, namely the attitude of a diverse scientific and engineering community to
computers. The attitude of commercial users has been studied by
Mulford (17). Little has been written about the attitude of engineers
and scientists and yet their opinions are crucial, since they have complete
freedom as to whether or not they use a system offered to them.
2.1 Concern for Data Security
The trend towards large computing systems in the early 1960s had
several effects. The operating systems became very much more complex
and the cost per hour of running the computer increased from pounds
to tens of pounds. Thus scientists who Ind been accustomed to the
"hands on" use of the central processing unit were in many cases
forced to work through the intermediary o f computer operators.
17 Thus the probability of both technical and human errors increased
simultaneously. Such errors could affect the user in many ways but
by fax the most serious was the loss of data files which might be
difficult or in some cases impossible to replace. Such incidents had resulted in extreme reluctance on the part of some users to commit large data files to the computers. Even after the introduction of time—sharing, data files on magnetic tape had to be handled by specialist operators. These problems were by no means peculiar to the Post Office.
18 2'2 Trade Union Interests
A project of this nature involves three major groups of staff. Engineering
draughtsmen have a long tradition of trades unionism. Union organisation
amongst computer operators and amongst professional engineers is a more
recent phenomena. Since computer graphics concern all groups early con-
sultation is advisable. The important thing to note is that all groups
have a valuable role to play in a successful graphics installation, but
dogmatism about specific tasks, such as who sits at the screen, must be
avoided. No serious problems were encountered, but details required
discussion. It should be noted that two factors contributed to the ease with
which these matters were resolved. Relations between the trades unions
and line managers in the PO Telecommunications business are generally- good.
(Judged by the currently prevailing standards in large engineering
organisations they are excellent). Secondlyldespite the oscillatory nature
of our economy the trend in the Telecommunications business is towards
expansion and large scale redundancies are not likely. An organisation
'n a less harm rosition with rpqrect to either of the above factors
should be cautious in the way in which it broaches the subject of
interactive computer graphics with its staff.
2'3 Working Outside Normal Hours A matter about which some professional staff voiced concern was the
computing tradition of round the clock working. With hatch scientific
computing this had been no problem since the work could be submitted
to the batch stream when the engineering staff went home. Time sharing
services are normally provided for uselin theory, at
19 the convenience of the designer. In practice the improved response
obtained in off-peak hours, together with a cheaper rate for the use
of the computer, provides some incentive for late evening working.
It is common for younger staff, particularly recent graduates, to fall
in readily with this arrangement, arriving late in the morning and
working late if this is renuired.
It was apparent to many that computer graphics eouipment, being expensive,
would also give rise to pressures of this type. Some staff expressed
their opposition to out of hours working at an early stage.
It is desirable that all attendance outside normal working hours be
on a voluntary basis. For some grades of staff overtime payments or
a shift allowance will be appropriate. The "flextime" system of
flexible working hours may have attractions to both staff and manage-
ment as a solution to this type of problem.
2.h Failure of Computer Teams to Meet Promised Dates
The timetables for the provision of computing facilities in the late
1960/s had slipped on a number of occasions. This caused many designers
to emphasise, when they were asked about their likely use for a new
computing system, that this depended critically on the date of provision.
If the computer was late, they would be forced to find other ways of
doing the work. Again , this situation was not peculiar to the P.O.
2.5 A Reluctance to Discuss Mistakes
Most of the paragraphs above- relate to failures by the computing
community to achieve their declared objectives. Howeverl manual methods are not perfect and the errors made arc often expensive. It is difficult
to get people to discuss their own mistakes frankly. The problem is
compounded by the fact that simple errors are the most common and it is
precisely there errors to which nceple admit most reluctantly. A 20 research engineer who may be prepared to admit to 7-, st errors of major technical judgement is most unwilling to disclose careless mistakes made either by himself or his staff. Printed circuit board design seemed narticu]ar]y prone to such careless errors.
2.' Hostility to Charging Systems
Several comnuter scientists, including Baron (27) have drawn attention to the fact that the complexity in job control languages exceeds that of the computer programming languages, which have now achieved a certain degree of standardization. Changing computers can be a traumatic experience for this reason and several groups who had suffered declared themselves unwilling to change computer systems.
2.7 The "Trojan Horse" Effect
Some hostility arises from a phenomenonthat may be described as the
Trojan Horse effect. The attitude arises as follows. Most engineers and scientists realise that computers will play an increasingly important role in research. The potential of computer analysis, simulation, and data handling, has been emphasised frequently. The impression has been given (probably correctly) that eventually a 1arce part of engineering research will involve computers in one way or another. Thus some technologists fear that if they allow a specialist comIuter group to participate in their project, or if they make use of a facility not under their direct 'control then as the role of the computer expands so will their own role diminish. The computer is seen as a potertial
Trojan Horse admitting ambitious comnuter personnel into their own research domain.
This attitude can he countered if the computer specialist projects himself' as a consultant who is prepared, or indeed anxious, to disenc--ce from cry project as soon as its originators assemble their own comnutirr expertise. 21 Simile .r problem- hove occurred before in technology. For example, the introduction of the transistor in electronics gave rise initially to specialist transistor design groups whose function was to design trans- istor circuits. Gradually these skills spread throughout the industry and now every design engineer is expected to possess knowledge of transistors as part of his professional skill. Computers have received
much greater public attention than previous new technologicsand this has created problems as well as opportunities.
2.8 A Lack of Confidence in Discussing Computers
The publicity mentioned above has had another unhelpful effect, namely a fear of appearing uninformed about cemputing techniques. Few specialists, confident of their own professional skills, are shy of admitting a lack of knowledgeofothertechnologies. However, some arc
shy of discussing computers for fear that a lack of detailed knowledge may earn them the totally unjustified label fold fashioned'. This problem should diminish as computing becomes an integral part of engineering first degree courses.
2.9 Over-Confidence in Computing
This is the inverse attitude of that mentioned above. It manifests itself in two ways. The first is a general conviction that computers must be involved in all future projects. There are soma cases in which this attitude is harmful. The second is more subtle and reflects some credit on successful work by compiler writers and operating system designers. Some technologists, experienced in the use of high level largunges from time shoring terminals regard such programming as typical of all computer programming. They seriously underestimate the problems encountered when programming in machine code or in time - dependent situations.
2a 3 RESULTS OF TP7 SUa77Y OF APPLICATIO'v'S The following paragraphs outline the results of the survey and follow-Up interviews. Information about several possible applications for computer graphics has been included despite the fact that some contained a speculative element and were proved impractical during the course of the project.
3.1 The Design of Printed Circuit Boards
Although the most obvious application for computer-graphics, this
application proved difficult to erpITe because of the large number of
variations of the existing manual method. These are illustrated in
figure 1. The technioues involved in PCB production are outlined
below. The draigner produces his circuit diagram. He then makes the
decision as to whether this is to be a single, double or multi-layer
board. (Multi-layer technology involves the insertion of an insulating
sheet between boards and a complex arrangement of interconnections
between layers). The last was not in use in the Research Department
at this time, but double layer boards were produced. The choice
between single and double sided boards was made by the designer on the
basis of his past experiences with circuits of a similar complexity.
This decision made, the board layout was produced on a drawing board,
either by a draughtsman in the central drawing office or by a designer
in his laboratory. The major problem is to produce a circuit hoard,
on which crossing connections on the same side are not allowed, from a
circuit diagram that inevitably contains connections crossing each
other. Moreover the circuit diagram takes no account of a component's
physical dimensions. This is largely a problem of topology but
depending on the circuit to be transposed there are e number of
electrical factors to be considered. These are listed below.
1. Components known to dissipate a lot of heat should not be
placed near each other.
23
FIGURE 1- ORGANISATION OF PCB PRODUCTION
Engineer Designs Circuit
Engineer or Technician DO.designs PCB Designs PCB in local laboratory.
Artwork Artwork Produced Artwork cut on local by Central Produceded on "Cut and Strip" Photographer DO "Cut and Machine Strip" machine
1 Boards Boards Manufactured Manufactured by Contractor Locally
24 *2. Power tracks are usually thicker than signal tracks.
Certain tracks that are used for very high frequencies must
not contain rectangular bends as these can give rise to reflections.
In some cases it is sufficient to chamfer the corner at h5 degrees,
in other cases an arc of a circle is required. h. Tn some circuits a large area of copper at ground Potential is created on one side of a double layer board. This is done to
screen components that may be mounted on the opposite side.
5. The length of a signal track may be significant for timing
purposes.
These practical factors have been neglected by some of the
theoretical papers on automated. PCB production, particularly these
relating to algorithms for automatic routing.
When boards are designed marually adhesive tape is often u sed
th- c-astion of tracks and Pads. There are imPortart differences
between analogue and dic7ital PCBs. The components for digital circuits
usually consist of rectan7alar duel-in-lire racks with considerable
repetition of circuit elements. Analogue circuits are less reou]er
and have a greater diversity of components.
The following paragraphs are taken chiefly from the notes of the
discr asion with users. They reflect accurately the factors considered
important by the potential users.
Switching Division
Production was estimated as 'Dein°. 100 boards per year. 50 to 60 of these
were new designs, the remainder were modifications. About 255 of all designs were modified at least once. There was thought to be a supprDssed demand that would appear if the provision of new facilities made it easier or
2q ouicker to de7i7-, circuits. The practice was to use pin wiring on general purpose boards. Double sided edge connector boards, size 8u x 11" were used, with up to h'd integrated circuits on each board. As many as 500 rins might be involved, so the practice was exnensive and relatively error-prone.
It took 5 to 8 man days to design a typical board using traditional methods which thus cost about £200. However the design cost for larger boards, eg the miniprocessor boards, was expected to be in excess of £300 per board. The cost of producing the artwork from the taped design was extra.
lia,veguide Division
PCB design was concentrated in one group, who produced about 100 boards per year. Another group produced about 6 boards per year. The total output of PCBs was expected to grow. 90% of components were DILICS. The number of ICs per board varied between 1 and 20, with an average of about
13. The frequencies involved approached those where the track length become critical and where rectangular bends could cause reflections. Thus a need for curved tracks and mitred corners was anticipated. The permittivity of the board was also a factor to be taken into account. Double-sided boards were used although one side might be used only as a copper earth plane.
Designs might be modified 2 or.3 tines. Some multi-layer boards had been produced using the services of a Canadian firm (turn round time for this service was about 5 weeks).
It was thought likely that designers would encounter power dissipation problems and hence a program which indicated likely temperature gradients was requested. It took 5 to 10 days to design a board. As the designers were professional engineers, the total design cost was somewhere between
£150 and f,'200 per board.
26 . Microwave Systems Division
One group produced between 20 and 30 boards per year. 70% of component
placements are ICs, mainly DILICS. Track layout was rectangular. 2 layer boards were used, one layer being used as an earth
plane. Co-axial connectorsidere used for crossovers. Up to 50 ICs were located
on a board 5" x 12", and it took an engineer about 5 days to complete the design.
Another group produced 10 boards per year and a third about 25 boards per year. All placements were DILICs, about hO% of boards are modified. The
groups used their own production equipment and took 2 to 3 weeks to produce
a board.
Data Systems Division
Double-sided PCBs were produced at a rate approaching 100 per year. Very
few discrete components were used. A fast production turn round was rcouired
and this was a problem with masks larger than 7" x 8", which had to go to
a contractor for photographic reproduction.
Customer's Apparatus Section
Production of PCBs was estimated at 30 boards per year. The circuit
technology involved was such that track lengths and precise component locations
are not critical. Apart from the cost of designing the boards by manual
technioues, the supervising officers were worried about the effects on the
morale of skilled technical staff which the boredom of manual methods produced.
Cable Transmission Division
It was estimated that 25-30 boards were designed per year. 15-20 ICs were
placed on each board, which took between 3 and 5 man days to design.
27 Postal Research Division
10 double-sided hoards per year were produced, the maximum size of which
was 16 integrated circuits. Some work wns contracted out to private companies.
It cost P.)!O for the design and production of a small board of P. inte.a.rated
circuits, end E45 for one of 11 integrated circuits.
Visual Telecommunications Division
A "low number" of boards were produced by one group.
10 boards per year were produced by another. High speed circuits were involved
and the facility to define track widths was required.
Miscellaneous Other Groups
The number of PCBs produced by all other groups was estimated at 30 per year.
Totals
The total for Research Department was 415 original designs per year.
There are 105 modifications to boards per year (estimated).
The Central Production Facility
The ResD Production facility produced 2,000 physical boards per year.
Large runsliere contracted out, so the number of boards produced in-house per
design varied between 1 and L. This fixed the number of original designs
plus modifications in the range 500-2,000, which confirmed the figure of
520 obtained by totalling the research groups, estimates. This check was
thought to be advisable as it had been suggested that there might be a
tendency for research groups to over-state their requirements.
The workshops had recently purchased numerically controlled machine tools
which could be used for drilling the component mounting holes in printed
circuit boards. They requested that any computerised system devised should,
if possible, produce ns part of its output the punched tapes necessary to
drive these machines. 29 The workshops provide facilities for etching single and double sided printed circuit boards, but could not produce plated through holes, although plans for the acquisition of a plated through hole facility were in hand.
29 3.2 Errors Occurring In The Design of PCBs by Manual Methods
A group produced its own art work but failed to observe the design rules
relating to the clearances between tracks. The production facility could
not produce the boards which had to be redesigned. Another group produced
art work that did not allow sufficient space for components to be mounted.
A third group sent art work to a small contractor who could not
manufacture the plated through holes. In each case long delays resulted.
Another group were still modifying the circuit while producing their own
art work. Several manually modified versions of the art work were in
existence and that eventually sent for production was not the latest
version. The boards produced were useless.
The scope for making each of the above types of mistakes is reduced by an
integrated design and production facility using CAD, where production
standards are written into the software.
3.3 Integrated Circuit Design
Integrated circuits consist of interconnected groups of transistors
manufactured by selectively "doping" areas of the silicon chip. Inter-
connection is achieved by etching the appropriate strips in a metallisation
layer. The final chip may be 4 millimetres square and will typically
contain 500 gates with two or three transistors per gate. The selective
doping of the base silicon layer and the creation of interconnections is
achieved by creating large (say 1 metre square) masks of "cut and strip"
material and reducing these to the required size photographically. A
large integrated circuit is created by the interconnection of many similar
small cells and conceptually the design problem is similar to the
production of PCBs. In practice the problems confronting the designer are
very different. These differences are outlined below.
30 ORGANISATION OF INTEGRATED CIRCUIT DESIGN.
Designer Produces "rough" Design on Drawing Board
Designer Amends or adds to Design
Input Data Input Data Coded using coded using the CAMP language Digitiser
"Digica" Program on B5500
CAMP Compilation on B5500
Accurate Flat bed Plotter Drawing
Final Mask Produced by "Cut and Strip" on the Flat-bed plotter.
FIGURE 2
31 The cost of the pure silicon used in the process is high and the economics of large scale integration are critically dependant on achieving a large cell packing density. Thus the automatic routing of interconnections, although theoretically possible, is not used in practice because it may lead to the inefficient use of silicon.
Rigid design rules with respect to clearances between the various layers of a cell must be followed. Failure to detect a violation of the design rules
(or a circuit logic error) early in the design process can lead to the production of inoperative or unreliable chips. Errors discovered at this stage are very expensive to rectify. Thus automatic checking for errors is a facility valued very highly by integrated circuit designers.
The design process is longer, and investment in a completed integrated circuit design is much larger than for a printed circuit board.
The field of integrated circuit technology is changing rapidly. Silicon gate, metal gate, complementary MOS and four phase logic are examples of technologies that have emerged in recent years. Although similar design techniques are used for each there are differences and it is a characteristic of computer aided design programs that apparently slight changes in design practice can greatly affect the utility of a program.
Manual design of integrated circuits became impracticable as the circuits grew larger and computer aids were employed. In the Post Office the CAMP system developed by the Royal Radar Establishment had provided a basis to which further subsystems had been added. Figure 2 shows the main methods of integrated mask design and manufacture. The masks to be produced consist of rectangular holes in an opaque base material, so the CAMP language is essentially a language to simplify the specification, manipulation and repetition of groups of rectangles and rectangular tracks.
32 Although an improvement on the manual method,the system described above
had several disadvantages.
1 Error correction was cumbersome
2 No automatic checking was incorporated
3 The CAMP compilations took a long time. This was at best
expensive and at worst became almost impossible due to computer
failures in the middle of the long compilations.
It was considered likely by the groups concerned that there was a suppressed
demand for ICs that would emerge if the design process became easier.
3.4 Integrated Circuits - Assessment of Reliability
In addition to manufacturing ultra reliable semiconductor devices in small
quantities the semiconductor groups of the Research Department are
consulted about the likely failure rate of integrated circuits designed
and manufactured by contractors. One objective is to ensure that, in
the event of one company failing to provide an adequate reasonably priced
supply of a circuit, a second source is available. The second source
could be another company or the PO manufacturing facility. The unstable
economic situation, with its consequential threats to the financial
stability of even large companies, has caused this aspect to become even
more important than hitherto. To ensure continuity of supply it is
necessary to have access to the original design data. As CAD becomes
widespread in the industry an increasing proportion of this design data
is computerised.
There are no defined industrial standards for either the medium or the format
of such data and this was a cause of concern to the groups concerned.
Thus a factor to be considered was the potential interchange of design
data with PO contractors.
33 3.5 Graph Plotting And Curve Fitting
Much computer generated data is ultimately converted to graphs. Many users ran small or medium sized programs to produce tabulated sets of figures which were then plotted by hand. In many cases these were time and frequency response curves for electronic circuits. These graphs might be plotted by the group concerned or might be submitted to the
Drawing Office. The introduction of time sharing had increased the number of program runs and this had increased the number of graphs produced.
Instructions had been issued to reduce the amount of graph plotting work submitted to the Drawing Off:Ice, because it was consuming a disproportionate amount of skilled labour.
An off-line digital plotter with a set of Fortran subroutines was available but this was not widely used for the following reasons.
1 Many of the computer users were deterred by the
task of understanding the subroutines and inserting them in
their program.
2 The job turn round time, which involved running the
programs, punching the tape to drive the plotter and plotting
the graph was too long for most users. It was never less
than a day and could be several days.
3 In the program development stage the determination of the
scale of the axes and the alignment of the annotation took
several runs. Each run was subject to the turn round time
mentioned above.
A detailed breakdown of graph plotting applications is given below.
34 Submarine Cable Group (39) Analogue circuit analysis programs developed by Neill were run in a time-
sharing mode on the B5500 computer for the design of transistor amplifiers.
The output was a frequency response curve.
Electronic Network Optimisation
Analogue circuit analysis programs were run from a teletype connected to a
commercial time-sharing bureau. These programs were written in BASIC.
Other programs written in ALGOL were run on the 803 -and 503 computers.
The Design of High Frequency Transistors
The group designed high frequency transistors and made use of digital
plotters to produce contours showing the concentration of impurities in
doped semiconductors. Programs to perform a single dimension analysis,
written in ALGOL, ran on the 503 computer. Work was in progress on a
2 dimensional program. This was written in Fortran and used a bureau
IBM 360/65 computer. A method of examining the doping concentration at the
various stages of the program run was required. A long term objective was
the production and display of complete models of transistors including
current flows in the semiconductor. Some animated films had been produced
in the United States using micro-film devices. (Presumably the computational
load was too great to allow the use of on-line graphics). The graph
produced had a higher aspect ratio than the cathode-ray tubes used in
existing display units. .
Mathematics Group
NeiI0s programs for the analysis of both linear and non-linear analogue
circuits were being developed by this group.
35 The topology of the circuit was represented by allocating a number to each node. Thus all the input data was numerical and was entered from a teletypewriter keyboard. The output consisted of tabulated functions representing the transient and frequency response curves. The programs concerned used advanced numerical techniques and during program development many runs of the programs were made. A rapid plotting facility would enable the programmer to examine the results of his latest alteration and correct errors with the minimum of delay. When the programs were complete the same facilities would be invaluable to the design engineers. They would be able to alter the input parameters and optimise the design by making a large number of runs from the graphics terminal.
The ultimate goal of workers such as Spence(57) was a fully interactive graphic system which would enable the engineer to draw his circuit using a light pens andthe maths group were receptive to the long term potential of such systems.
High Frequency Cable Characteristics
This group measured the frequency response of coaxial cables at a wide range of frequencies and at a range of temperatures. Their major tool was a large temperature controlled chamber into which cable drums, weighing several tons, were manoeuvred on a hovercraft. The frequency run was automatically controlled and the results were logged on paper tape. The manoeuvring of the drums and the time taken for the chamber to achieve temperature stability rendered the process time consuming and hence fairly expensive. Furthermore the work load depended on the delivery of cables from the cable manufacturers and could peak unevenly. A quick,efficient, and reliable method of handling the data thus produced was essential. The existing practice was to feed the data tapes into a teletypewriter connected
36 to a timesharing Honeywell computer 7_,rogrammed in Fortran. This was then used to produce the tapes necessary 7.-,o drive a drum type digital plotter but a quicker method of examining the graphs was required. Hard copy, in one form or another would still be required. The tabulated results were also required for record.
Microwave Systems Groups
Time and frequency response curves were produced by the programs running on the University of London Atlas Computer. A graph plotting facility was required but hard copy was essential.
Another group designed amplifiers with specified non-linear characteristics and had a program written in Algol running on a timesharing bureau Honeywell computer. This calculated the required frequency responses.
Millimetric Waveguide Systems
Investigations into the properties cf helical waveguides required the plotting of the solutions to the waTeguide equations as a function of a frequency. A time sharing bureau PDP10 was used to produce numerical results which were plotted by hand. The programs were written in Fortran and the group had once suffered a serious loss of data Files (not on the
PDP10).
Data Transmission Groups
Extensive use was made of fast fourier transform programs and a graphical
display of the sampled time and frequency response was required. An Algol
program for the design of group delay equalisecg had proved useful and would
have proved more so if it had had graphical output.
37 Data and Telegraph Transmission Group
Equalisers were designed using programs written in ALGOL on a bureau
Honeywell computer. Frequency and transient responses were calculated from a circuit for varying component values. The group saw little need for facilities to alter the circuit (other than to change component values) interactively but saw an immediate use for a quick method of viewing results. The provision of graphical hard copy facilities was also considered important. Program routines to draw and scale axes were required.
Transmission Performance Assessment
This group designed systems. The objective was the determination of the frequency response obtained from telephone circuits comprising of a number of system. components connected in series. These components included cables, amplifiers and equalisers. In some cases it was necessary to determine which arrangement of system components would give the desired frequency response. Programs were run on a bureau time sharing Honeywell computer.
As in the case of analogue circuit design,graphics could be applied in two stages. The first would involve the plotting of the output curves, the second would involve input to the program by the interactive manipulation of the system components. The symbols would be those representing the system components rather than those used in circuit design.
Assessment of Local Telephone Circuits
Equaliser datawere logged on paper tape. This was printed and curve,
fitting was carried out manually. Graphs were drawn of the curve
38 derived from calculations for various values of the equation coefficients.
These were then compared with the curve produced by the experimental data.
The curve that gave the best fit determined the value of the equation coefficients that best represented the observed phenomena. Experience had shown that human judgement was desirable in selecting the best fit curves so a fast method of plotting the data and curves would be an asset. The end product was a set of numerical coefficients but it was important to retain a copy of the graphs produced in the fitting process.
Human Factors Research
This research is concerned with the ergonomics of telephone customers' apparatus (ie telephone handsets, dials etc) and of switchboards. The work includes the recognition of telephone signal tones and the determination of response times and error rates when the equipment is used. Experiments, controlled by Elliott 905 anclArcturus Computers are conducted on large numbers of subjects and large volumes of data are produced. The results are punched on paper tape. Thereafter the curve fitting operation is similar to that described above.
3.6 Program Evaluation and Review Techniques (PERT)
PERT was well established in the Post Office. The display of the diagrams was a possible application of graphics.
(43) The work by Cloot at Imperial College had been noted and the Production
Engineering Association were known to be working in the field. The prime interest was in the Research workshops.
3.7 Machine Shop Scheduling
The problem is to match the available machine tools and skilled operators
39 to the work in hand and to give management advance notice of problems and of failures to meet agreed timescales. A scheduling program for use on
batch computers was being developed by the University of Lancaster. Part
of the output of this program was to be machine tool loading diagrams
produced on a line printer. The use of graphics for the display of these
diagrams would facilitate the use of the program in an interactive mode.
A more fundamental approach was to reduce the actual scheduling problem to
graphical form and for the operator to solve it interactively. Published
paper144) indicated that the method had promise but it was recognised that
much research would be required to produce a viable system.
3.8 Programming of Numerically Controlled Machine Tools
Mention has already been made of the intention to derive drilling tapes from
the PCB design programs. Three general purpose machine tools were also
used for other applications and were programmed by hand. It was
theoretically possible for a part to be drawn at a graphic screen and the
tape produced directly from that sketch. Accurate dimensions could be
entered from the keyboard. However, the problem did not warrant the
amount of research that would have been required.
Even without this sophisticated approach there remained a promising
application. The machines were programmed either directly in the tool
machine code or indirectly using the 2CL language. In the latter case
the program was entered by teletype and compiled on a time - sharing
bureau PDP10 computer. The machine tool program tape was produced on
the teletype punch. Whichever way was used there was the problem of
verifying that the tape would drive the cutting head along a path that
was (i) safe (ii) certain to cut metal to the desired shape. The existing practice was to first cut a block of polystyrene. The machine tools cost about £20,000 each and were thus one of the few research tools whose time was of comparable value to that of a medium sized computer. Programming errors towards the end of a long part program were expensive. A method of displaying the shape represented by a program tape would enable the part programmer to check his work and rectify errors before they reached the machine tool.
3.9 Accommodation Plans
The opening of new research projects and the closure or contraction of others necessitated a continual re-allocation of available accommodation.
This could be a complex procedure, following the stages shown below.
Stage 1 Research groups specified their requirements.
Stage 2 Accommodation group produced a provisional sketch, taking into account the availability of space, ventilation, water, cooling water, natural lights, toxic extract, drainage, gas, high pressure gas, tele- communications and staff association agreements.
Stage 3 Drawing Office measured the areas and produced the drawing(s).
This takes between 1 and 5 man days; the maximum time to complete the job may be 3 weeks.
Stage 4 The agreement of all parties concerned is sought. If complications arose the job returned to stage 2 above. In some cases it could be several months before the job leaves this loop, and many man hours might be involved.
41 In the preceeding 12 months about 750 drawings had been produced. Four drawing office assistants, average salary just under £1,000 were allocated to this work. The scheme could be automated in stages. The first would be to provide a symbol manipulation facility and digital plotting package for use in the drawing office to assist in the rapid production of drawings from sketches produced in the traditional way. This could be extended so that the display and light pen are used by the accommodation group. In this case the computer would be programmed to contain details of the floor layouts and the provision of services. This facility was required most urgently.
The final stage would be to program details of the various constraints involved, so that a warning of infringements could be given to the man producing the layout. It is important to note that the final decision would always rest with the officer, not the computer. A schematic of the postulated final system is given below.
Structural information about buildings Drafting standards and symbols as defined Data entered into the by drawing office library using the Accommodation standards as defined by Digitiser the Accommodation group
(All the above would represent a once off effort)
Draughtsman and/or accommodation Duty Officer Display and use the display when a new drawing is Light Pen required.
Drawing produced within minutes of the C Digital Plotter- layout being decided
42 These ideas were discussed with the accommodation groups, who were in favour of proceeding with the scheme, providing that it could be implemented without diverting very =uch effort from their day to day work.
The scheme would be more suitable fcr the proposed new buildings, as they would be of modular construction. The average drawing took the planning officer about 8 hours to plan, and a drawing office assistant 12 hours to draw. Labour costs totalled £28 per drawing.
3.10 Flow Charts and Coding for Stcred Program Control Telephone Exchanges
The group concerned were interested in a computer aided programming system to ease the task of writing programs to research aspects of SPC Telephone exchanges. The first stage of such a system could symbol manipulation.
The programmer would manipulate flow chart symbols using a light pen until he was satisfied that the displayed flow chart represented his intentions.
Simple checks and constraints could be included in the program, for instance the user could be notified of a failure to specify both routes from a conditional branch. A copy of the completed chart would then be made.
Possibly the program could be extended to provide automatic code generation from flow charts. Research into this problem has been carried out by
Van Dam at Brown University and by the RAND corporation and 40)
A problem of displaying complex diagrams was anticipated if a small screen was used, but this could be overcome by the use of software and/or hardware windowing techniques, which would enable different sections of the diagram to be viewed in close-up. Laser displays also have potential where large screens are required.
An advantage of such a system would be improved program documentation, because good copies of all flow charts would be produced automatically. (41) The 1968 NATO Conference on Software Engineering , aimed at avoiding the
43 expensive programming disasters of previous years, placed emphasis on the production of accurate flow charts. It was noted that Bell Labs had (42) developed the ESSFLOW program to assist flow chart production for the
ESS1 project, and quoted a throughput of 5000 charts per year. An initial use of about 3 hours per week was foreseen, although if successful this could grow considerably.
3.11 Computer Assisted Drafting
A number of published applications for computer graphics were concerned with various aspects of Drawing Office automation. The use of a graphic screen and digitiser to produce part drawings from complex assembly drawings was discussed with the Drawing Office. It seemed that the number of part drawings produced in this way was small and the assembly drawings involved were often complex (eg steerable aerial assemblies). This did not indicate that this application deserved much effort.
Use of the graphic screen and light pen as a sophisticated drawing board had some attractions because of the ease with which errors could be corrected. The flat bed plotter could be used to produce the final drawing. This aspect, which would require relatively simple software, was thought to be worth development as a general tool for the Drawing
Office.
A request for an automatic drafting facility was also made by the switching technology group, who maintained their own file of logic diagrams. 139 diagrams have been produced in the proceeding two years and about one third of these had been amended between one and four times (average twice). It took a junior engineer between one & three days (average two) to produce each drawing. Thus four man days per week were devoted to the work. The cost of updating the file of drawings was estimated at 2.55 per week. Various logic simulation programs were in use and once in computerised form the data used in the preparation of the drawings could be used by the simulation programs.
3.12 On-Line Production of Spectrograms
Research was carried out to determine the effects on speech of analogue telephone circuits with varying characteristics. Spectrograms are plots of time against frequency with the signal amplitude for a given set of time frequency coordinates indicated by a density of shading. They were produced for each circuit. under examination. Banks of filters Nm.E) used, and the analogue output was used to drive pens on a drum recorder.
Alternatively, sound was recorded and the filtering process simulated digitally on an Elliott 503 and the spectrogram produced on a line printer or plotter. On the 503 the digital filtering of vocoder speech had taken
50 times real time and was expensive. With a powerful computer connected to a graphics display the production of spectrograms in real time became a possibility. This would have enabled many more samples of speech to be analysed. Since most displays allow only limited beam modulation, a technique for displaying graduations of bone would be required.
3.13 Readability of Alphanumeric Characters
Displays (often numeric but sometimes alphanumeric) are being used increasingly in telecommunications and a variety of methods are used to construct characters. One device may use a grid of lines while another uses a matrix of points. The evaluation of the effectiveness of these methods was a human factors research problem. Rather than gather a collection of hardware it was thought that it might be more convenient to
45 simulate the devices using computer graphics although it was recognised that
extreme care would be necessary to avoid inaccurate results caused by the
characteristics of the graphics displays. The intention would be to display
the simulated character at a given time then record the time that the subject
took to respond (say by pressing a button with a similar label) using the
central processor real time clock.
Flicker is undesirable in display technology and the storage tube was
considered to be a potentially good tool for this work.
3.14 Decision Networks
A decision network is a flow chart with multiple start and end points. The
graphics display would be used to display the parts still available to the
decision taker after he had exercised each of his options. A possible
application was the routine of new circuits through the existing telephone
cable network. A possible managerial application was the decision networks
used by training officers in recommending a given course of further study
'to students with differing qualifications.
3.15 Deriving Models of Transistors
Reliable mathematical models for new semiconductor devices were required.
An experiment was proposed whereby the measured characteristic of the
device under test would be displayed on a graphics screen. The characteristics
computed using the computer model would be superimposed. The model
characteristics would be adjusted by the experimenter until the two curves
coincided.
46 3.16 Thin Film Technology Circuits
Only one group (Microwave Radio) was producing these circuts, at a rate
of about 1 per month. The design problem was similar to that posed by
PCBs and ICs although the technology was different.
3.17 Text Editing
A recurring problem in all industrial research organisationsis the
delay in the production of edited research reports. In addition staff
concerned with the production of administrative reports often spend a
disproportionate amount of time editing and checking drafts before an
error-free version is produced. This problem is acute where several
levels of management have to approve a report before it is issued. An
attempt to solve these problems using computer graphics had been made
by the Hypertext system(46) . This has been described as follows:-
"the operator can insert or delete arbitrary sized blocks of text
at any point and can easily, for example, move a paragraph from one
position to another. Using this system the delay between the draft
stage of document and final typing can be reduced from days to hours.
The original draft is entered into the machine by a typist, the
author can then view the whole draft on the screen either by
flipping pages or by scrolling. He can add text, move sentences
or paragraphs from one position to another, and correct spelling.
When he is satisfied with the final version on the screen all he
has to do is call for line printer output of the final document".
The computing solution to this problem requires printers and displays
with upper and lower cases or, where'book' quality is required,the_ output can be direct to filmsetters. L SUM= OF THE GRAPHICS EQUIPIENT AVAILABLE The equipment available on the UK market can be categorised as follOws.
47 4.1 Storage Tube Terminal
The dominant characteristic of the storage tube terminal is the fact that once a picture has been created it remains visible without being refreshed, so there is no need to store the information to be displayed at the terminal. Thus a storage tube terminal which includes character and vector generators and a keyboard can now be sold for around £2,000, although the price was about 24,300 four years ago. The rate at which information is transferred to the screen can be low, so that the computer power required for display maintenance is small and the bandwidth of the line linking the terminal to the computer can be low. The picture does not disappear if the response time of the computer rises, so storage tube terminals may be used on time sharing computer systems. The device is intrinsically flicker free and operates in moderately high ambient light conditions. No air conditioning is required and the terminals are small and quiet enough to be placed in a general office or a laboratory. They are easily transportable.
The main disadvantage of most storage tube terminals is the lack of selective erasure. Information can be added to but not deleted frcm a picture. The picture can only be changed by complete erasure followed by redrawing, and this can take minutes. It is not possible to create moving pictures or to use a light pen and this makes it difficult to use the tube for the input of information as distinct from output. Another device must be used for input so a keyboard is associated with the terminal.
Devices for inputting XY co-ordinates, such as joysticks, thumbwheels and tablets are available but are of rather limited use in the absence of a moving picture facility.
A prototype storage tube terminal with selective erasure facilities was developed by the Marconi Company. The individual components of a picture could be erased without disturbing neighbouring components. Simple
48 moving -pictures, for enariple the manipulation of symbols to build up circuit diagrams, could be produced and graphical input as well as output was feasible. A transparent stylus activated tablet was developed and was placed on top of the storage tube so that the user could draw pictures by moving his stylus over the screen. The result was a cheap alternative to the light pen. The facility for deleting individual components of a picture implied that the data on which the picture is based is held in core store and this increased the demands made by the terminal on the computer. The picture quality was rather poor and the terminal was physically large. In the event this terminal, which seemed promising, was never placed on the market.
Most users will require a hard copy of selected pictures, and this can be achieved in several ways. The simplest is to re-draw the picture on a digital plotter. These machines produce accurate drawings of a high quality but are slow. A Polaroid camera may be used to photograph the screen. This method is quick and the camera is relatively cheap (£250) to buy, but the price of a copy is 35p. To overcome the disadvantages of the above methods new hard copy units have been developed for use with storage tubes. The picture is re-drawn on an internal cathode ray tube, the light output of which is coupled by a fibre optic faceplate to dry silver paper. The process takes about 18 seconds and a good auality copy is produced. These units cost about £2000, and the price per copy is 3p.
4.2 Refreshed Displays
The picture is drawn on a random scan basis and must be refreshed, say, twenty times per second to prevent it flickering or disappearing. The data must be stored in a readily accessible form and in practice a small local computer is dedicated to the display. Such systems may operate either in stand alone mode or as satellites to larger systems. They
49 offer full moving picture facilities and are the most versatile of all displays. Prices started at around £10,000 but most practical systems cost about £60,000.
4.3 Storage Tubes with Local Computers
These systems attempt to exploit the low cost of the storage tube while circumventing the lack of a moving picture facility. A high speed parallel data interface is used to permit the rapid redrawing of the picture when an element is to be changed. By adjusting the voltage levels on the storage tubes a very restricted part of the picture is drawn in refreshed Mode so that one element of the picture may be moved.
Graphical tablets are used as a substitute for the light pen. This type of equipment costsfrom £20,000 to £45,000.
4.4 Television Type Terminal
A TV monitor, which is cheap by virtue of commercial mass production, is used as the display unit. Picture dataam held in a small local store.
The picture is bright and individual elements may be deleted but the amount of detail that nay be displayed is low.
4.5 Automatic Drawing Systems
A display, usually a storage tube, is used in conjunction with a digitiser and plotter. The display is used to effect small modifications to drawings, which are created by traditional methods. The digitiser/plotter is the main component of these systems. The price range is £15,000 to £45,000.
4.6 Other Developments
The equipment categorised in paragraphs 4.1 to 4.5 covers the options available when the choice of equipment for this project was made. The past few years have seen continuous development in this area. Elliott & ( ) Fenwick reviewed progress in 1971, and further developments have
50 taken place since These arerevieued in section 9 below.
5 THE DERIVATION OF A STRATEGY
With such a large number of potential applications and so many types of equipment the number of approaches that could have been adopted was large.
Because storage tubes which were relatively cheap)appeared suitable for the graph plotting and curve fitting applications (which did not require moving pictures) it was decided to proceed immediately to the acquisition of a terminal. Because the capital investment involved was low no rigorous financial justification was to be produced before the purchase but the resulting applications were to be scrutinised rigorously after the event.
The storage tube terminals were also seen as having a potential use for the verification of tapes for numerically controlled machine tools.
It was obvious that the other major applications would be the design of printed circuit boards and the design of integrated circuit masks. These would require more interaction than the storage tube terminals could provide and this implied the use of refreshed displays, or at least storage tubes with local computers. The capital investment required was thus higher and would require a financial justification before it was authorised. To a large extent, the project split into two distinct investigations which are described in sections 7 (work with Storage Tube Terminals) and 8 (work using Fully
Interactive Graphics) below.
6 NON TECHNICAL FACTORS IN THE SELECTION OF INDUSTRIAL EQUIPMENT
The process of selection of computing equipment in industry is often influenced by non-technical considerations. The first is the application of general procurement policies. In private industry this is likely to be in the form of an instruction to purchase equipment from companies within the group.
51 For example the semiconductor division may be instructed to purchase CAD from the groups computer division, despite a technical preference for equipment made by a different company. Similarly a group marketing turn- key CAD systems may be forced to use a central processing unit provided by its computer division despite the availability of cheaper or better processors elsewhere. Two examples of the above were encountered during this project.
In the European public sector this instruction to purchase from an explicitly named source may be replaced by a more generalised instruction to purchase from either National or EEC suppliers. The severity or otherwise of the rules (ie whether relating to the company ownership, the location of component manufacture, or the location of assembly) varies according to the
Government of the day but the general trend of the policy in most European countries has been the same for the last 20 years.
Another factor is the absolute importance of choosing suppliers that can be relied upon to provide an adequate 5 or 7 year maintenance contract. This requirement often excludes the products of small companies that attract academic attention. Products from large foreign companies may
be excluded where the UK marketing rights are given to small organis- ations.
the contracts or buying departments in most organisations reserve the right not to place contracts with companies considered by them to be financially insecure.
7 WORK WITH STORAGE TUBE TERMIN_AI,S
7.1 Selecting the Terminals
All terminals on the UK market in 1972 used the Tektronix 611 storage
tube. This has a screen size of 15cm by 21cm, a guaranteed life of
200 operating hours and a probable life of 4000 operating hours.
(Replacement tubes then cost £370). There are 1024 resolvable points
52 on the loroer edge of the screen and 760 on the shorter. An 0 optional feature on some terminals is a small strip along the bottom of the screen with the non-retentive qualities of an ordinary phospher.
By refreshing this at an appropriate frequency it can be used as an erasable scratch pad memory to facilitate the composition of messages entered from the key pad. Similarly by careful selection of the velocity of the eletron beam a faint erasable marking can be made on the screen. This is usually used to display a cursor or pair of crosswires. TJhen moved under the control of a joy stick or a tracker ball such crosswires.can be used to define a pair of X-Y coordinates which, with suitable software, can be used to identify an item on the screen. The features mentioned above were common to all DEIST terminals on the UK market. when one comes to the control circuits the user has some choice of facilities, and must decide which are worth paying for. All terminals have hardware vector generators. Most have hardware character generators and this was considered essential because its omission degrades per- formance in two ways. A typical 2 dimensional cartesian graph will contain about 150 alpha-numeric characters (including axis annotation).
If no hardware is provided, a software character generation routine must be entered for each character, and this is time consuming. Instead of transmitting one ASCII character to line for each character required, about five vectors, each requiring 4 ASCII characters must be sent. At 1200 Baud it will take 26 seconds longer to transmit 150 characters.
Some terminals include a hardware curve generator to achieve further data compression. Using this, a graph might be defined by 3 segments, each requiring 8 ASCII characters. This would have required about 150 vectors
(600 characters) without the hardware. A saving in transmission time of 6 seconds is achieved at 1200 baud. However, this is partially offset
53
Figure 2a
54 by an increase in computing time. The majority of data to be displayed originates in a tabular Cartesian-like form and a curve-fitting routine must be entered to produce the parameters required by the hardware. This may be worthwhile for some three dimensional applications but it is unlikely to be economic for the 2 dimensional work on which the terminals were to be employed.
In the event a Tektronix 4002 Mk II terminal with a refreshed strip was chosen. A 4601 hard copy unit and a Polaroid camera were also obtained. This equipment is illustrated in figure 2a.
7.2 Choice of Communications Link
The use of the switched network enables several computers to be accessed from one terminal. Unless very heavy usage can be guaranteed it is likely to be cheaper than a private wire. On most timesharing computers the switched network input ports were operated at 110, 600 or 1200 baud. Picture generation time for a given terminal is a function of line speed. A typical two-dimensional cartesian graph can be drawn in 4-8 seconds at 1200 baud. As this delay is superimposed on the time- sharing system response it is unwise to operate at lower speeds if this can be avoided. There is no necessity to operate the return channel at the same speed as the channel from the computer to the terminal. The rate of data generated at the terminal is limited by human factors. A
75 baud channel (available in full duplex with a 1200 baud channel on the GPO datel modem number 1A) is capable of handling the data generated by keyboards or X-Y probes but cannot handle the data generated by a graphical tablet. This modem was chosen.
7.3 Software for Graph Plotting Several comprehensive graphics packages already existed and some of these could be used for the production of 2 dimensional cartesian graphs. One does not lightly develop new software if this can be avoided, 55 and these were considered to see if they met the PO research requirement.
Most existing packages were developed for refreshed graphics, digital
plotters or DVSTs connected directly to local computers. While some
are sufficiently general to be adapted for use on remote storage tube
•terminals they are not optimised in that direction. Many packages consist
of.subroutines, to be inserted by the user in his program. Our experience
with digital plotters had shown that the use of device dependent I/O
routines was itself sufficient to deter a significant proportion of our
users who were accustomed only to running high level language programs
via Dartmouth type system commands, even though the routines in question
might appear simple to computer professionals. Another disadvantage of
the subroutine approach becomes apparent when the user makes mistakes in
scaling and/or positioning his axes, or in his annotation. . The
correction entails editing his source program and recompiling, a lengthy
process if he has to travel round this loop several times. Our digital
plotter experience had shown that most users did indeed require several
runs to get their graphs correctly formated.
An improvement on the subroutine approach is the extension of an existing
high level language by the addition of special graphics statements.
Unless the language is interpreted (eg FOCAL), which is not usually the
case, alterations still entail recompilation. In either case the
graphics facilities are limited to users of the language in question,
and we required our facilities to be available to users of any language
on a given time-sharing system. We also required the package to be
easily transportable from one time-sharing system to another.
Several existing packages offer 2 dimensional facilities as a subset
of generalised 3 dimensional perspective viewing facilities. For some
applications these facilities are essential, but for the average user '
they may imply unnecessary program complexity or run time overheads.
56 Finally, our examination of• existing software showed that some packages tended to be u.nsatisfactory-intheir implementation of small but important details, such as the formating of numbers and the positioning of scale
"tick" marks on the axes. Our requirement was for a package that, although limited to 2 dimensional graphs and curve fitting applications, was extremely easy and economic to use, and produced a highly polished. finished product.
It was decided to write a new package called "CUPID" (a conversational utility programme for information display).
7.4 The Objectives of CUPID Summarised
1 To facilitate the display of data in newly created or existing computer files as graphs, histograms and other two-dimensional represent- ations.
2 To be very easy to use.
3 To produce the highly polished end product that could be used in the research reports without further drawing. 4. To be easily transportable from computer to computer. 5 To be economic
7.5 The Design Philosophy of Cupid
Two modes of use are allowed. To facilitate the easy modification of plots an interpretive command processor is used to analyse the user's commands. Usually these are given interactively from the terminal but they may be inserted as subroutine calls in the user's program These commands (and parameters associated with them) when analysed provide numerical information which is placed in the picture information file.
An exception is the plot command. This activates a PLOT routine which takes the information from the picture information file and the named data file and sends it to line. Default options are inserted in the
57 command processor for every command omitted by the user (except the name of his data file) Figure (3) shows the way in which the package is used, and a simple example is given in figure ( 4).
7.6 The Log.
When deciding which facilities were to be implemented it was uncertain what commands would actually be required. It was decided that a log be automatically kept of all command usage and all messages (which included error messages). Thus an on-going record of the way in which people use the programme would be obtained.
7.7 Details of the Implementaion
Fortran IV was chosen as the programming language to achieve maximum transportability. The program would be written as an application program to run under the control of the timesharing executive. A time sharing bureau PDP 10 was chosen as the computer to be used. The standard file structure of this computer was used as the interface between
CUPID and the application programs. The CUPID command language syntax is given in AppendiKB . A hash table with chained overflow was used for command identification.
58
USERS DATA FILE
PLOT T4002A
USER CUPID COMMAND PICTURE LANGUAGE INFORMATION PROCESSOR
INTERACTIVE USE
I•••• it ••••• =IS - •••• •••• eM■ Me eme •••• mmo •••• Mem mie• ••■ mm OM dome •me oft Nee - ••••• - Mb IWO SUBROUTINE USE
USER • PROGRAM
CUPID INFORMATION FLOW (SLIGHTLY SIMPLIFIED)
Figure 3
59
E.722.1PL111 OF THE USE OF CUPBJ
Typed Command Comment
DATA FREQS User s7lecifies the name of his data
PLOT The command Processor inserts all default ()lotions required
to produce a graph of the data,
and produces a graph. Thus a
picture is produced using only
two commands.
MIS 100, 120 The user now tidies up the x-axis
'AXIS 0, 100 The user now tidies up the 7-axis. PLOT A new graph is produced.
FIT 4 A fit of degree 4 is made.
PLOT Produces a graph of the data and the fourth order polynomial.
Figure LI.
60 7.8 Cupid Facilities
AXES
The following features can be specified for the axes of a 2 dimensional graph.
1 Type (Linear, log, log-probability)
2 Range of values
3 Increment size 4 Tick or grid lines at the incremental points
5 Annotation format (eg Integer or floating point)
6 Frame (the lines opposite the X and Y axes may be present
or omitted)
7 Picture size and position on the screen
EXECUTIVE
An executive routine provides the following facilities
1 Dumping of picture information to disc.
2 Reloading of picture information from disc..
3 Listing of data files on the screen
Status command reminds the user of the options he has
exercised so far
DATA POINTERS
The data to be plotted is specified as follows:-
1 Specification of disc file names
2 Creation of data sub-sets from:
a) Different columns within the data file
b) Different items within columns (eg every second item)
3 Data input from Tektronix keyboard or teletype paper-tape
In addition the type of symbol to be used at the data points and the
type of line connecting them can also be specified.
61 WINDOWING
The user can examine selected areas of his graph in close up by selecting (or
"probing") 2 points using the crosswires and joystick. These points are taken as the approximate upper right-hand and lower left-hand corners of the window. To minimise errors the actual window is placed just "outside" the probed points.
The following facilities are available:-
1 Zoom in
2 Automatic rounding to axis marks
3 Automatic reset on zooming out
Figure 5 illustrates the operation of this facility.
VECTORS
1 Insertion of vectors (For framing, underlining, pointing etc.)
2 Deletion
This facility is intended only to enhance the appearance of the graphs; no attempt is made to provide full symbol manipulation facilities.
TEXT
1 Insertion. The starting point is defined by the crosswires and the text entered from the keyboard
2 Selection of double size or italics
3 Moving the position of predefined strings
4 Copying predefined strings to other positions
5 Erasing
6 Automatic centering within frame
7 Choice of horizontal or vertical text
CURVE FITTING
The following facilities are available
1 Least - squares polynomial up to order 30
2 Display of coefficients and goodness-of-fit
3 Removing unwanted fits from the data structure (Removal from the screen entails re-plotting the picture) In addition to curve fitting, a smoothing algorithm is provided. 62
EFFECT OF WINDO=G
o.k-
Wind w selected J10:3
, Probed point
-2
-0.
-0.
Figure 5
63 7.9 User Reaction to the Hardware
In all important respects, our users have been satisfied with the performance and ergonomics of the equipment provided. The resolution and picture quality of the storage tube have proved adequate for most applications, although some users have complained about distortion when observing detailed graphs with multicycle logarithmic axes. A number of features originally thought to be desirable such as the refreshed strip, double size and italic characters have proved unnecessary, and the cheaper versions of the DVST terminal now available would be adequate for this work. Hardware character rotation is appreciated when vertical text is displayed. The joystick is satisfactory, provided that sufficient space is left around the terminal for left and right handed operators to position the unit where they wish.
Apart from a slight hum from the cooling fans, the equipment is silent, and has been used satisfactorily in a general office environment. The only potential limitation here is the level of ambient light, and this was not found to be serious provided that venetian blinds were used in summer sun- light.
Paper tape facilities, not provided with the DVST terminal, were required on a number of occasions, and were provided.
The Datel 600 service is adequate for this application at both 600 and
1200 b.p.s. Picture distortion due to line noise does occur, but it is easily recognised and it was not frequent enough to seriously inconvenience the user. Some use of the system at 300 b.p.s was unsatisfactory.
The provision of convenient hard copy facilities proved crucial to the success of the project, as we found that users require at least one permanent copy per four graphs displayed. Table 1 compares the methods that have been used. The use of hand drawn sketches was not foreseen by the authors, but was observed in use on some occasions. For most purposes
64 TABLE 1: A.COMPARISON OF HARD COPY FACILITIES
1 Polaroid Hand Drawn Hard Plotter Sketch Copy Unit Film
Is it easy to use? Yes Yes Fairly Fairly How much does it cost per copy? Nil 5p Sop £2 + How long does it take? seconds seconds minutes minutes or hours
Does copy deteriorate? No Yes No No
Resolution Poor Fair Good Excellent
Can copy be reproduced on:- Xerox Yes Yes No Yes Offset litho Yes Yes No ' Yes Overhead slide Yes Yes No Yes 35mm slide Yes Yes Yes Yes
Can size and aspect ratio be altered? Yes Slightly No Yes
Can copies be produced in colour? No No No Yes I COUTAHIMATIO0 LEVEL V LUAU tIOLE RADIUS FOP VODICUZ PQCS.VJ7:::1 1.E-7 t.r-n orttortooto•tnot•vorn•ov•t,■*w tt• — ot••••ott tr, •
I aat,rtt.to otnentottooloGINCYS
••••••10.110111... fo.%11101•1110011..01.011111112to .1+ •P" ..es ___ 4
ts.....couat•wa•••-zo crtuu, -cot, • " I Sftwomsonst,-rot*
ousammoontamotto•ma•01.••••.1
J
• • I -3 .-t000to .•••••••••...
•
ot.o. to tn.,. ott
11,
, W 1 1
•tralinlYIMIIIMME•Wo..., —0•4•11•••••■•■••••••sra, .1 , • 4.1 00 1S0 200 240 2C0 • 3C
HOLE SIZE INICROHS) the hard copy unit is best, but the camera was used to obtain copies for publication purposes and the plotter was used to obtain an accurate copy of the final version of some of the more complex graphs where picture distortion had proved a problem. Figure 5Ris an example of such a graph.
7.10 User Reaction to the CUPID Software
A major design objective of the package was that it should be easy to use, and this has been achieved. Staff at levels ranging from Branch Head to laboratory assistant have operated the system, and all have been pleased with its simplicity. Comments on the facilities provided have been more varied. More people than had been anticipated require polar graphs but the plot itself can easily be produced by converting the co-ordinates and the lack of scales has not proved serious. Some users, having used and expressed their appreciation of the two dimensional facilities, have requested three dimensional representations. The exclusion of 3D representations in the interests of economy and simplicity was correct and these facilities are best provided outside CUPID, especially as they are already available in several excellent graphics packages. CUPID has fulfilled its function by meeting the needs of most users and revealing the full potential of computer graphics to those that wish to progress further. An analogy may be drawn with high level languages such as BASIC and JOSS, which often serve to introduce naive users to the more advanced programming languages.
The package has been supplied to the following organisations.
Hatfield Polytechnic
Imperial College (Dept of Physics)
University of Glasgow
National Engineering Laboratory
66 Hawker Siddely Dynamics
Selenia (Italy)
Time Sharing Limited (for general use by its customers)
Institute Max Von Lau, Grenoble
It has not been possible to carry out a scientific survey of user reaction in all of the above organisations because of the time involved and because of problems posed by commercial security. All the comments received were favourable regarding the ease with which CUPID - could be used and its general utility. Apart from Hatfield, where the program was found to occupy more core store than was allowed to programs under its timesharing system, the only problems encountered related to conversion between computers and these are described separately below. The National Engineering
Laboratory described it as "the most useful piece of application software that we have" and casual comment in the trade press was also favourable.
7.11 Case Histories Involving the Use of CUPID
When the DVSTs and the CUPID software had been in use for about one year a survey of its use was made. A description of some of the applications is given below.
SEMICONDUCTOR APPLICATIONS
This research was being carried out to gain an understanding of the diffusion processes in gallium arsenide crystals over a range of temperatures. An analytical solution was considered but was extremely difficult. A numerical solution was possible but involved a power series of 32 terms. At a given temperature range most of the 32 terms would not contribute. The group had very little computing experience (described as
"rusty Fortran II") but were encouraged by the existence of CUPID to tackle the problem by analysing the power series. Sets of 11 curves, each
67 with 50 points were drawn on logarithmic scales. The irrelevant variables
were identified and eliminated. Some problems arose because the resolution
of the storage tube proved inadequate for the volume of data to be displayed
and some hand plotting was necessary but even so it was estimated that the
work which would have taken 10 days by hand was done in one day. The
provision of a high precision digital plotter would reduce the time further. Figure 5A shows a typical graph.
THE DESIGN OF MICROWAVE TRANSDUCERS
Polar graphs with 400 points were plotted using CUPID. The conversion
between cartesian and polar coordinates was done by the user's program.
The absence of polar notation on the resultant graphs was not important
because the shape of the curves, rather than the exact angle of any given
point, was important. 12 plots were produced for each coupler and five
couplers were designed. It was estimated that 15 minutes using CUPID save
a technician 6 hours manual work.
.COLOUR TELEVISION SIGNAL SIMULATION
Complex polar graphs, each of about 1000 points,were required to simulate
vector scope measurements. The graphs would take about 5 hours to draw by
hand and were produced in 10 minutes using CUPID. Figure 6 illustrates a
graph with 600 points. Little use has been made of text.
LOCAL TELEPHONE LINE MEASUREMENTS
Graphs illustrating best fit polynomials were required for a series of 75
sets of experimental results. Each fit required an average of 4 plots.
The work was carried out in 33 hours using CUPID and would have taken 600
hours to do manually. A typical graph is shown in Figure 7.
68
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• C t7 ••■k:...MMANIIIMINIAMINIMON•MIWAIIIMIONOMA Iti$ 25 23 • 45 5G 05 - 75 05 05 105 PRJH LINE CURRENT-HILLIANPS R.3.2 12 JUNE 1972 TIME AND FREQUENCY DOMAIN PLOTS
As anticipated these constituted a large part of CUPID use. A typical graph is shown in Figure 8. The local telephone line group produced 24 for one investigation. These were produced in 72 minutes using CUPID and would have taken 6 hours to produce manually.
MICROWAVE MULTIPATH PROPAGATION EXPERIMENTS
Sets of graphs, about 60 in all, were prepared illustrating the results of a propagation experiment. CUPID was used for 3 reasons. The information was required quickly for presentation in a report. Thus speed of preparation was more important than the cost, which would in any case be small compared with the cost of the experiment. 3 graphs, each with logarithmic scales, were required on the same sheet of paper. No commercially available graph paper met the requirement but the CUPID picture facility enabled this difficulty to be overcome. This illustrates an important facet of CUPID namely the users ability to create, via the hard copy unit, a sheet of graph paper tailored exactly to his problem.
Figure 9 shows one of the sheets in question. Note the extensive and flexible use that has been made of the text facility.
OPTICAL FIBRE INVESTIGATIONS
A totally different example of the value of computer graphics occurred in this. work. A long investigation into the properties of fibres for use in optical transmission systems was being carried out involving experimental observations and computer analysis of the results. Several hundred computer runs had been made and extensive data files existed. Inconsistencies were being encountered and it was not known whether these were due to a fault in the computer program or the experimental apparatus. This situation had persisted for 4 months. Using CUPID it was possible to scan
71 Figure 8
APIA. I TUDZ: VOLTS
o 1 • 0 co fa • • • • • • • • • • • • cb to 0 0 O 0 0 0 0 0 re a 0 . U 0.- o . Iii s • 0 o 0 re t 0 0 (.3 Pt .
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03 0 E3 (A o s 0 0 CI rs ado e o Q %.1 ce, re e o at o . r..,) m e o o up E.I m s .1 0 W •• -;.• i I . MENDLESHAM PROPAGATION EXPERIMENT CUMULATIVE DISTRIBUTIONS AS AT 23/55 31/12/73 CROWFIELD—MENDLESHAM 7.SKM PATH CAUSE 07 FADING ALL CAUSES MULTIPATH AND 0/C PRECIPITATION +40
+30
CO Q NI. • N 1 +20 1 1
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LEGEND PERCENTAGE OF TIME THAT ORDINATE WAS EXCEEDED —.-0:10.S5GH2 ....aIS.GSGX2 --m35.30GH2 back through the data files, and produce graphs of variables not previously
plotted against each other. Within 2 days the cause of the inconsistencies
(a computer program error) had been found and rectified. Figure 10
illustrates a typical graph. It would have taken many months to produce (16) the graphs by hand. Larkin describes a similar experience at UK AEA
Culham, and similar instances of error detection have occurred in the use
of computer graphics in ship building. This example is considered important
because the experimenter, using computer graphics, was able to gain a
visual impression of his data in a way which would not otherwise be
possible, and thus detect errors.
BRANIN'S ZERO HUNT AND THE VERIFICATION OF RANDOM NUMBERS
All of the above uses of CUPID have been for the production of fairly
conventional graphs. The two examples below illustrate less usual
applications. Branin's Zero Hunt is a numerical algorithm for the solution
of non-linear differential equations.
A member of the mathematics group working on linear circuit analysis had
read the method. In order to gain an understanding he produced a plot
showing the values of the variables at various stages of the process for
different initial values. This is shown in Figure 11. Had the DVST not
been available no attempt to produce the curves by hand would have been
made. Because they were available his understanding of the problem, and
also his job satisfaction, were marginally increased. It is difficult to
quantify the value of such exercises but they are real. Another unusual
use was a visual presentation of random numbers from files used in the
simulation of telephone exchange traffic. The number is plotted with
itself as ordinate and its predecessor as abscissa. No lines are drawn
between the points. Points are added, then the process is stopped to
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uniformly, without intensity bands in any direction, it is likely that the
numbers are truly random.
It has been assumed in each of the above cases that the cost of computing
the data to be plotted is independent of the I/O device used. The estimate
of the time taken to do the work manually may in some cases seem high.
There are 3 reasons for this. For complex graphs, the time taken to
extract the data via the teletype terminal at 10 characters per second is
significant. When a large number of graphs (eg 75) or a large number of
points (eg 1000) are to be plotted manually time consuming errors are made.
The work is often carried out by junior staff and boredom becomes a
problem when long series of graphs are to be plotted and the person
concerned would rather be doing something more interesting.
7.12 The Cost of Using CUPID
Discounted cash flow (DCF) is the criteria often used for assessing the
•economic viability of new projects in industry. Income and expenditure
are corrected to allow for the investment potential of the money involved
and then summed over the period of the project. If the net flow is
positive, the project is profitable. Some difficulties are encountered
when applying the technique to the provision of computer services for a
large number of users. There may be a conflict with the budgetary system used
to control research expenditure. Each research project is, after
assessment, allocated a budget for man hours, computing services and
materials for use in experiments. Once a manager has been allocated his
resources under the various headings it may not be easy to incur extra
expenses in one category even although this may produce savings in another.
Sometimes the restrictions are real. For example man-power is a genuinely
77 inflexible resource and it is not always possible to achieve actual monetary savings when labour is saved by the introduction of a computing system.
In other cases the restraints are rather artificial. A change of plans which leads to excess expenditure being incurred under one heading may be interpreted, ( or it may be feared that it may be interpreted ) as lax project control even though the decision will be sound according to the
DCF.
Before he will take a decision to use a new computing facility a project manager will need to know the cost of using the equipment. This can only be calculated if the amount of use to be made of the equipment is known.
In other words the charges for the facility depend on the number of others choosing to use it.
A final difficulty stems from the peculiar nature of software.
The concepts of depreciation, Write-off period, and residual value
are well developed for hardware. Software written in machine code
can sensibly be written off in the same period as its host processor
But a package which is in high level language will prove useful
until the language becomes obsolete or until there is no need for
the program in question. In order to perform DCF calculations
assumptions about all these factors must be made but they may be
rather arbitrary, and the DCF is sensitive to their validity.
CALCULATION OF THE TIME TO PLOT AN "AVERAGE GRAPH" BY HAND
Number of times CUPID was used in 18 months as recorded in the log is
2409 (See Appendix A).
The number of hours for which CUPID was used as recorded in the log is 399.
78 TABLE 2
EXTRACTS FROM THE CUPID LOG (APPENDIX A)
HOURS CPU MINS. PER CONNECT TIME HOUR CONNECT TIME
28 1.68
57 1.38 21 2.46 20 2.58 24 2.6L 16 1.62 21 2.04 57 2.76 26 0.90 8 2.28 121 1.56
1.86 CPU minutes Per Hour Connect Time (Average)
CPU Cost for 10 minutes @ 7.5p per second is £1.39 (Average)
79
TABLE 3
SUMMARY OF INFORMATION FROM USERS
Estimate of Estimate of No of
Application Time to Plot Time to Plot Graphs by Hand (Hrs) by CUPID (Mins)
Multipath Propagation 21 6 8
TV Signals 15 5 10
Local Telephone Lines 150 4 13
Wave Guide 1f8 6 15 1 Fourier Analysis 48 3 3
Average time to Plot by Hand 3.9 hours
This is taken as 4 hours in subsequent calculations, since it is based on
estimates.
Average Time to plot by CUPID. 11 minutes
This figure is used only as a check for the figure of 10 minutes obtained from
the CUPID log. The correlation is good.
NOTE: The figures in column 1 above differ slightly from those
given in the "case histories" because anticipated future
jobs have been taken into account.
8o If one assumes that one graph is plotted for each entry, then it takes
10 minutes to produce a plot. The package can be used to produce several
graphs per entry so an error here would make the calculations below more
favourable to CUPID. The number of graphs produced in 1 year is 1600
(approximately). To perform the DCF we must first calculate the direct
costs of preparing graphs by hand and by using CUPID. Of the various cases
histories described above 5 were analysed in greater detail. The five were
chosen for analysis because they were typical of the "large volume" users.
This information is summarised in table 3. The hourly charge for the grade
of labour used to ploy graphs was, at 1972 rates,Z1.50.
Thus the average cost per graph plotted manually was 4 x £1.50, ie. 26.00.
The cost of the paper used is estimated at 2p.
The total cost by the manual method is thus £6.02 per graph.
Using the computer it takes 10 minutes. Computer costs are £8 per hour
for connect time and 7.5p per second CPU time. Thus the computer costs
for CUPID are £1.33 (connect) and £1.39 (cpu , as taken from table 2).
Labour costs using CUPID are £0.25 (10 minutes @ £1.50 hr). Hardcopy cost
using CUPID is £0.05.
The total cost using CUPID is £3.02. The saving in direct costs is thus
£3.00 per graph, for the first 3 years, rising to 1,4.36 (see below)
We now have all the information required for the DCF shown in table 4.
Apart from column 4, all amounts of money are in units of £1,000.
Column 7 = Column 5 - Column 2.
Column 8 is the product of columns 7 and 6.
81 Column 9 is obtained by summating the totals in column 8 up to and including the year in question.
YEAR 1 (1972)
The terminal hardware costs include thee -Tektronix 4002A terminal (£5,500) and the hardcopy unit(J2000). Had a DVST not been used a teletypewriter costing
£500 would have been provided for computing purposes. The cost attributable to the project was thus taken as £7,000. No allowance has been made for the maintenance of the DVST terminal. For an electronic device the cost of maintenance is about the same as for a teletypewriter despite the greater capital cost.
The use of early versions of CUPID did start in the same year as the programme was written.
The development of the program took place on a bureau computer. Disc storage charges were quite high and constituted an unforeseen overhead.
YEAR 2 (1973)
No disc storage charges were incurred because the package was placed in the bureau library. The package was not readily accessible to users on others so use was remained rather low.
YEAR 3 (1974)
Conversion to the new IBM 370/168 took place. Despite the objective of making CUPID portable difficulties were encountered in the conversion, mainly relating to the communication routines and file access between user programmes under VSO. Substantial conversion costs were incurred.
Portability is thus the only objective that the package failed to achieve..
82 A 7 year period is normally used for computers within the PO so the DCF is taken to 7 years after conversion to the 370/168, making a total period of
10 years in all.
YEARS 4-10 (1975-1981)
These figures are estimates, but care has been taken to ensure that they are as accurate as possible.
The cost of disc storage has been allowed for the CUPID package. The cost of a replacement storage tube has been allowed in year 6.
The price of raw computer time on the 370/168 is about 25% of the price of time on the bureau computer due largely to the economies of scale sometimes known as Grosch's law. It is estimated that the VSO operating system could, in the worst case, absorb about 50% of this advantage with an interactive package such as CUPID. Thus it has been assumed that the computing costs
(connect time + CPU charge) will be 1 x (£1.33 + £1.39) or £1.36. This increases the profit per graph by £1.36 for these years.
The DCF shows a profit of £59,670 after the repayment of interest. A sensitivity analysis shows that the accuracy of the figure actually achieved, (as distinct from projected) will be particularly dependent on the accuracy of column 3, the number of graphs plotted per year. It would be dangerous to make predictions about most activities in scientific research since they are technology dependent. However graph plotting is not, and is performed for both experimental and computational investigations. It is an activity likely to stay constant or to increase during the period under consideration.
It has been the practice to disregard the effects of inflation, in DCFs and to assume that it will affect old and new methods equally. This convention,,
83 developed in the days of moderate inflation rates, is now being questioned
(eg by Bowden(30)) since in days of high ( ) 20%) inflation it may militate against investment in high technology industries. The chief cost of plotting graphs by hand is labour, which is likely to increase sharply in a period of, high inflation. The major costs in the CUPID project (the terminal, the new computer, and the software) were all incurred at the beginning and will remain constant during the period. If inflation remains high the rate of discount will increase but the overall effect will be to increase the profitability of labour saving projects like this.
The calculations shown below are intended to find the break even point for an organisation starting a project similar to CUPID now. It is assumed that the organisation produces similar graphs to the PO (which are large graphs) and that it uses similar DCF costing policies. It is also assumed that it would not be involved in a computer changeover during its costing period, that the man hours taken to write its own package are similar to those taken for CUPID, and that its computer charges are similar. Small costs have been neglected for simplicity. The cost of a storage tube terminal plus a hard copy unit has now fallen to £4,000. The capital charges are thus —
Terminal Hardware z4,000
Development charges for the Software
(Labour) £5,000
Development charges for the Software
(Computer charges) £3,000
TOTAL £12,000
The annual charge to recover at 10% over 7 years is, using discount tables,
£12,000/5.2478. (assuming that the first savings occur in the first year.) This gives an annual charge to recover of £2,287.
84 1 D
TABLE 4
No of Saving # Net Discounted Total Discount Cumulative Tear "CUPID" Project Expenses Graphs Per Cash Cash Saving fact or DCF Per year Graph Flow Flow
1 Terminal Hardware - 7.0
(1972) Software (Labour) - 5.0 1,600 £3.00 + 4.8 1 -19.7 -19.7 -19.7
Computer Time( ?DP ) -10.0
DISC Storage - 2.5 -24.5
2 1,600 £3.00 + 4.8 .9091 + 4.8 + 4.36 -15.3
(1973)
3 IBY: Conversion (Labour) - 5.0 1,600 £3.00 + 4.8 .3264 - 3.2 - 2.64 -17.94
(1974) IBM Conversion (Computer) - 3.0
Total - 8.0
4 Disc Storage - .36 4,900 £4.36 +20.9 .7513 +20.54 +15.43 - 2.51
(1975)
5 Disc Storage - .36 4,800 £4.36 20.9 .6830 +20.54 +14.03 +11.52
(1976)
6 Disc Storage - .36
(1977) dew Storage Tube 4,800 £4.36 20.9 .5650 +20.14 41.38 +22.90
Total - .76
7 Disc Storage - .36 4,800 £4 .36 20.9 .513 0 +20.54 +10.54 +33.44
(1973)
85
No of Saving Net Discounted Total Discount Cumulative " Project Expenses Graphs per Cash cash Tear "CUPID. Saving factor DCF per year Graph Flow Flow
8 Disc Storage — .36 4,800 £4.36 20.9 .467 +20.54 + 9.59 +43.03
(1979)
9 Disc Storage — .36 4,800 £4.36 20.9 .424 f 20.54 + 8.71 +51.74
(1980)
10 Disc Storage — .36 4,800 £4.36 20.9 .386 -t- 20.54 + 7.93 1-59.67
(1981)
Total Profit in 1972 £59,670 Cash Terms
86 The profit per graph will be £4.36.
Thus the number of graphs per year to break even is 2287/4.36 or 524.
This is approximately 2 per working day.
7.13 An Analysis of CUPID Command Usage
The information headed "commands-frequency of use" in the CUPID log
(appendix A) gives details on the way in which the package was actually used.
When studying the figures it is wise to ignore the- sheet dated 30 June 1972
since that initial period included training sessions in which all the
facilities were demonstrated. Certain commands listed in the usage tables,
such as TIME, SNOOZ, DEVIC, EDIT, PAGE, WAIT, should be ignored since they
are primarily there for the benefit of systems programmers and in many cases
are not even included in the user's manual. Once we have excluded these atypical cases we see that:-
1 RETURN has not been used. RETURN is the command used to return control
to a user program when CUPID is used in its sub-routine mode. The lack of
use of this mode emphasises the popularity of the interpretive mode with
users It is,howevexwossible that some users have taken parts of the
package and used them in subroutine mode without using RETURN.
2 Every other command has been used at least once in the period although
in many cases the use has been low. It might be argued that, for maximum
cost effectiveness, commands used only two or three times in a year should
be pruned from the system but it has been decided not to do this. User
convenience and a highly polished end product were major objectives of the
package. The removal of any command that has been used, even infrequently,
must detract from the achievement these objectives. The cost, both in core
store and computing time, of keeping commands in is slight.
87 3 Commands enabling the user to define his own scales (Xspan, Yspan, etc) were heavily used. This indicates that the automatic scaling routines were
used only for the initial quick look, after which the user did his own scale
definitions.
4 The text command is used extensively for the annotation of graphs.
5 The curve fitting routines are used frequently. Curve fitting, as
anticipated, is a major requirement for users of this kind of program.
6 Of the "highly polished" facilities the choice of line type and symbol
are most frequently used.
8 FULLY INTERACTIVE GRAPHICS
It was apparent that the PCB and IC applications would require a greater degree of interaction than a DVST terminal with a low speed link could provide. A refreshed system, or just possibly a DVST with a local computer, was required.
It was also apparent that, because a working system was required quickly, it would be necessary to purchase both the hardware and the software. Two sets of criteria were used to select the system. These were the acceptability of the display hardware and the overall effectiveness of the hardware and the software as a problem solving system. Some notes are also included below on the configuration of refresh systems because of the importance of this topic but;because
of the adoption of the turn-key approach, this was not an aspect that figured crucially in the selection.
8.1 The Display Hardware
88 Focus
This is good on most modern displays and often a manual adjustment is provided for the operator's use. It is possible for one area of the screen to be in focus while a slight but irritating fuziness occurs elsewhere. This is easier to recognise when characters are being viewed. A short program to write characters on the five main areas of the screen (ie the centre and each corner) simultaneously was used to reveal this defect. An example from a storage tube system under test is shown in Figure 12.
Picture Distortion
This can be caused by hardware faults in the X and Y amplifiers. It is more likely to affect the corners and extreme edges of the screen. The display of a
"Union Jack" or rectangular grid pattern was helpful in identifying the trouble.
Uneven Line Quality
This is caused by the effective intensity of the beam being reduced by a high scanning speed. It can occur when long vectors are drawn and affects storage tubes more often than refreshed displays. It was revealed by the union jack pattern mentioned above. Figure 13 shows a picture taken from a storage tube system under test.
Jitter
The elements of the picture may oscillate slightly on the screen. The fault may be caused by inadequate smoothing of power supplies and is rather more likely to be present when equipment designed for use with an American 60 Hz mains supply is adapted for use in the UK. Any of the test programs mentioned above would reveal the fault if it exists, but it was not found to be widespread.
Resolution
Each manufacture will quote the number of resolvable points for the X and Y
axes. This figure is important because it,rather than screen size determines
the amount of information that can be displayed on the screen. It was
neither practical nor necessary to check that this resolution exists at each
point, 89 13d3CA 1315101 artirb cs-ml corlon. X=J73 XUVUT* MOST CS/OSY 00080. Wale •;
13COCA JALIHD giVIONM XWVUT2 C2t0SY ecceat.
13CDaA 1302001 JALItiD JXLtNA AOROmm 140q0:111 xuvuTZ X!VUT! CtIOSY CCIOSY eacaae 110%080 ,•• • • • • • • ME: • • mft.I.M• • • • MI II • • • • • 1 r • •la •• • • I I - ••••••■•••••••11 ; !M.
•
Fig 13
91 but a program to draw a set of five vertical and five horizontal lines in each of the five critical areas of the screen was run.
Registration
When the same co-ordinates are used at different times in a program, the resultant physical points may not exactly coincide. With a refreshed system this causes a gap between lines that should be joined. A program to draw a series of squares, with all the vertical strokes drawn before the horizontal strokes, is an adequate test for a refreshed system. A further test may be applied to storage tubes by redrawing any complex picture without erasing. Any disCrepancies between the traces were immediately visible, and this particular fault was encountered more than once.
Sensitivity to Ambient Light
Most systems are sensitive to both ambient light and reflections from the screen surface. For most applications this is not serious but tests may be necessary if there are restraints on the environment in which the display is to be used. Hoods ore often provided to shield the screen, but these are inconvenient if more than one person wishes to look at the picture.
Flicker
For each refreshed display system there is an upper limit to the total length of vector that can be drawn before the picture starts to flicker. Flicker occurs when the time taken to trace a picture exceeds the time in which the first parts of the picture to be drawn start to fade away. It can be caused by either software or hardware limitations. It can be tested by a program that adds vectors of known length (most conveniently the full width or height of the screen) under the control of the operator. Vectors are then added one at a time until flicker occurs. Similarly it can be arranged that blocks of text are progressively added so that the maximum amount of text can be tested. This may be important for displays with software character generators. This aspect was considered important.
92 Use of the Light Pen
This applies only to refreshed systems. The speed with which the system reacts to light pen interrupts is a function of both hardware and software.
Most manufacturers supply the software necessary to manipulate a cursor under the control of the light pen. The speed with which the pen could be moved without losing the cursor gives some indication of the response to be
expected when the system is used for symbol manipulation.
Afterglow
Some cathode ray tubes have too much afterglow, which causes
moving objects to leave a "vapour trail" behind them. Reaction to the
phenomenon is largely subjective, and can be gauged from the light pen
cursor test mentioned above.
Damage to the Screen
This is a reliability rather than a performance factor, but it is conveniently
investigated along with the performance factors mentioned above. Some
cathode ray tubes, in particular storage tubes, are liable to incur damage
to those areas of the screen used most often. If the tube on which the
tests are being performed is new, little can be learned about its
susceptibility to this trouble, but if it has been in use some time, a
program to write on each area of the screen might reveal potential problem
areas.
All of the above phenomena are well known to engineers concerned with
display design. However, it was the author's experience in this series of
tests that the hardware problems mentioned occurred with greater frequency
than one might have hoped, bearing in mind that many of them were noted on
demonstration sets installed and maintained on the manufacturers' premises.
No displays can be expected to achieve perfection and, once the user is
aware of the problems, the decision as to what is acceptable is largely
subjective. Display performance, however, is one of the few areas in which
a subjective judgement is ultimately the most important. 93 THE CONFIGURATION OF REFRESHED SYSTEMS
Most published work on the subject of display performance has concentrated on the problem of optimising the hardware configuration that supports the display. The most eloquent statement of the problem was published by (6) Meyer and Sutherland who coined the phrase "the wheel of reincarnation".
The problem is as follows. One starts with the concept of a display as a peripheral, taking its data from the parent computer. It becomes apparent that performance can be improved by adding to the display hardware and thus relieving the main c p u of routine tasks. This process continues until the display hardware has assumed the characteristics and cost of a small
processor. At this point one attempts to improve the utilisation of this
new processor by inserting more hardware between it and the display, and thus the second turn of the wheel has begun. That it is very difficult to
determine the optimum point on this wheel can be appreciated by listing the variables that exist in a satellite system. These are: the power of the main processor, the performance characteristics of the host operating
system (not always accurately known), the power of the satellite computer and the capabilities of the display hardware. Much research has been done,
and a. wide range of designs from different points on the wheel marketed.
Each designer claims to have found the optimum point, but these claims are
hard to evaluate because of the difficulty of estimating the demands that
each display will make on the host c p u. Modern designs tend to be at least one turn round the wheel (ie they embody hardware equivalent to a
small computer) and prices have fallen since the early days of graphics.
No well defined formula exists to enable the user to choose the optimum
configuration for a given application. Skyrme (7) has attempted a
classification of application programs, but was handicapped, by a lack of
data on program behaviour, a situation reminiscent of the early days of
EDP performance assessment. He also gives a table showing the inter-
dependence of graphic system variables, which, although useful, 94 is lacking in quantitative values in the crucial areas of running costs. (59) A mathematical model was developed by J. D.Foley who also noted the lack of data on application programs. 8.2 Assessing the Performance of Problem Solving Systems
The problem is to decide which of several systems will perform best when
used by many people to solve many problems. The mathematically correct
solution is to perform a large number of experiments with the samples of
people and problem sufficiently large to be statistically significant. The
cost of such experiments would soon exceed the cost of the equipment being
evaluated and a cheaper procedure is required. Two approaches were tried
by the author with some success. The first is a benchmark approach in which
one designer attempts the same problem on a range of machines. The problem
is more difficult than conventional benchmarking because, having solved the
problem on one system, the designer approaches the next with a knowledge of at least one valid solution. Errors due to this cause can be reduced if the benchmark designer has already tackled the problem by manual means, so that each of the systems being appraised is approached with the same prior knowledge of a solution. The second approach is to select a number of designers or design teams, allocate them time on the display, and to ask them to form their own opinions of the equipment by tackling either new work or old problems. The results of such exercises can be fruitful, and a wide variety of comments can be expected. Usually one will obtain a consensus of opinion on the merits of the equipment concerned.
If serious disagreement does occur, it can be assumed that the benefits to be obtained by using the equipment are marginal. Such an exercise will usually cost about £250 per system, but could cost as much as £1000 if a complex system is investigated thoroughly. It is important that the assessment exercise involves designers, and is not left entirely to computer staff, since there is some tendency for those of us in computing to overrate
95 technical ingenuity and to neglect practical details that are important to the user.
In this evaluation two bench-mark tests were used, one for PCBs and the other for ICs. For reasons of commercial security, it is not possible to tabulate the results fully, but a summary of the results is given below.
Again for reasons of commercial security the systems are referred to by code letters. Notes are also given on some systems considered in some detail but not bench-marked.
SYSTEM A
This display, which was claimed to be the second in the US Sales league was marketed by a small electronics firm in the UK. Miniature magnetic tapes were available for a low cost storage. It had a 21 inch screen and its price of £70,000 was low compared with other large screen systems. A comprehensive drawing package was available for about £8,500. This package had an organised data structure and would lend itself to the draw ing applications described in section 3.11. The marketing company were developing microfilm units and hard copy devices which were of interest.
The disadvantages were the small size of the marketing company for maintenance and, crucially, the lack of PCB and IC software.
SYSTEM B
This display had a well designed graphics programming language and proven
PCB and IC programs available at extra cost. It was the only display of
British design and manufacture. Its disadvantages were a rather poor picture quality, and a lack of support for some peripheral devices. A suitable system would cost £12,000. Considerable interest was expressed in this system but the company ceased manufacture before the end of the evaluation period.
96 SYSTEM C
This display had been sold extensively in the USA and had a large screen.
Its manufacturer recommended connecting it to a medium size computer and insisted on a full sized line printer. This brought the total cost of the installation to about £120,000. Air conditioning was not required. Picture quality was excellent and the company had a good record for both software support and hardware maintenance. The software included
a Fortran graphics package and some graph plotting routines but these had
not been backed by an organised data structure. This was the best hardware system but it was not thought to be worth the extra money compared with other manufacturers. The company made tentative proposals to negotiate the lease of IC design packages used within their own manufacturing
organisation, but never quoted a price for the software.
SYSTEM D
The chief feature of this display of US Manufacture was its 22 inch screen,
which was an asset. The UK marketing company withdrew the display from the
market during the evaluation period after failing to make a sale in the UK.
The US manufacture continued to market the hardware but not the software.
The software system design seemed heavily weighted in favour of satellite
mode working, rather than stand alone working.
SYSTEM E
This display costs £67,000 and was one of the cheaper displays. Picture
quality was good. Miniature magnetic tapes were available as a low cost
storage medium and there was good support for other peripherals such as
printer plotters. Proven software was available from a UK software house
for PCBs and IC mask design, and the PCB package had been sold widely in
Europe and in the USA. Extensive bench-mark tests were successfully run
97 for both the PCB and IC applications which immediately made the equipment a front runner for selection.
SYSTEM F
This display was marketed in the US for use with the manufacturer's large computers. It was not available for test in the UK.
SYSTEM G
This cost around £30,000 but could not work in a stand alone mode. Technically it would have been possible to operate it as a terminal on bureaux computers but neither of the bureaux concerned expressed much interest. The line and bureaux computing charges would probably have spoilt the economics of the scheme in the long term and there was no graphics packages available on either computer.
SYSTEM H
The company supplied details of their new display, based on an established range of mini-processors. The screen size was 21 inches and software included Fortran subroutines and a data base but no electronics, PCB or drawing packages. Applications were mainly in medical research. No prices were quoted. The system was not selected because of the lack of suitable software.
SYSTEM I
This equipment was displayed at the US Trade Centre but the manufacturer had not then found a UK marketing agent. It was based on conventional design principles but by cutting hardware facilities to a minimum (eg 14 inch screen and no hardware character generation) the costs were reduced to something under £9,000. It could be used effectively in a stand alone
98 mode for simple tasks but connection to larger computers could have easily been effected using low speed lines and input channels. It was an interesting hardware development but was not suitable at that stage because of the lack of suitable software.
SYSTEM J
This was a large screen refreshed display that had just been made available in the UK. A software house was considering implementing PCB and IC software on this display which would have rendered it attractive, but this could not happen soon enough to meet the required timescale.
SYSTEM K
This was a complete hardware/software system. Its major components were a storage tube, a graphical tablet to provide interaction, a mini computer and a suite of programs oriented towards IC design but usable for PCBs.
It had an ingenious method of interpreting user defined characters drawn on the tablet as manipulative commands. The method of interaction was less convenient than for a refreshed display and during a 3 week trial most PCB and some IC designers expressed dissatisfaction with the facilities. The system was thought unlikely to provide an adequate substitute for a refreshed system. Its cost between £30,000 and £40,000. The period of the evaluation coincided with the power cuts in Britain. This caused hardware problems and illustrates one of the practical difficulties in doing a scientific evaluation of systems such as this. It was realised that the advent of frequent power cuts might have influenced the comments of some of the bench-mark workers but resources did not permit a repeat of the 3 week trial.
99 SYSTEM L
This is based on two storage tubes and a small computer. Prototype software
for PCB design was provided and a final version was promised within a year,
if suitable customer or government support was forthcoming. The bench-mark
designers had the exclusive use of the system for one day and several design teams attempted trial designs. The consensus of opinion was that the
display had potential but that more software was required before it provided
the facilities required.
In view of the uncertainty about provision of the software the system was
rejected.
It will be seen from the above, that, because of the lack of suitable
software on most systems the situation did not arise whereby a detailed
comparison of bench-mark results was required.
Instead the existence of the
bench-mark served to establish the existence, rather than the efficiency,
of a suitable package. As a result of the comparison described above it
was decided that System E (which was a DEC PDP 15 with a VT 15 display),
together with software provided by Redac Limited, was the most suitable
equipment. A costing exercise comparing the use of this equipment with
manual methods was carried out to see if the capital expenditure was
justified. The original discounted cash flow is reproduced, without
alteration (Table 5).This has been done to facilitate its comparison with
the results actually achieved. This comparison of the anticipated and
achieved costings is useful because it highlights areas of economic
sensitivity in projects of this nature.
100
8.3 Original Calculations on the Cost of PCB Design
These calculations were performed in 1972. No attempt to correct the monetary values for inflation has been made. The calculations were made to slide rule accuracy. The PO possessed a flatbed plotter, purchased for the production of
Integrated circuit masks. There was free time on it that could be used for PCB artwork without further capital expenditure.
DCF over 5 years at 10% Interest rate (table 5 ) showed that the project will show a profit in excess of 290,000 (1972 values). 5 yearsa instead of the usual 7, was used because the use of refreshed graphics equipment was considered by the financial advisers to be more risky than conventional computers.
The running Costs for a Computer Graphics System (Min. Configuration for PCBs) were required for Column 1 and were computed as follows.
These Costs occurred in years 1-7:-
Accommodation, 350 sq ft @ £3.68 per sq ft £1,300
1 time of one Computer Programmer on the Maintenance of the software purchased £2,000
Maintenance of Hardware £3,250
Line Printer Paper, Electricity £ 500 Total £7,050
In Year 1, the programmer would devote all his time to the PCB work, adding
£2,000 to the support costs for that year.
2 PCB design staff in Research Dept. would receive software house training costing an additional £750 per man in Year 1. In year 2 the
Post Office would organise in-house training costing £2,000 for other
PCB designers.
101 Costs of PCB design using existing Manual Methods for column 3 of the DCF
415 New designs per year
Costs vary between £80 and £300 per design
£150 was taken as the cost of an average PCB, based on an
examination of typical boards
Thus the total cost of New designs = £62,300
105 modifications @ £75 each ( estimate) £ 7,880
Total annual costs under the existing system - £70,180
Labour Costs Using C.A.D. system (Excluding computer time and overheads)
Assume that it takes 4 hours to design an average PCB using computer graphics.
Designers time will cost £8. Data prep will cost £2.
Labour costs will be £10 per new design.
Modifications will take 1 hour and cost £2.
It has been assumed that 175 new boards will be produced on the computer in the first year, and 350 (out of a total load of 415) will be produced on the computer in subsequent years.
The DCF Table showed that the purchase of a refreshed display was justified by the PCB application. As it was the intention to use some time to investigate other potential applications, a knowledge of the hourly cost of running the display was required. This cost was calculated as shown below.
Let x be the annual charge to recover the total cost (excluding the software packages) taken from Col 4 of the table:
102
-- C: C. A. a Sysl-em • 1 ' , lxisting Mods Cost Mods Cost Dis- Computer Aided Design Costs %irs Cost Cost Bds Year D.F. 0 by 0. Nan- 0 Man- 0 Total counted System C.A.D. £10 pb C.R.D. £2 pb ually £150 pb ually £75 Total 1 1 70,180 Hardware 67,000 175 1,750 50 100 240 36,000 55 4,125 -59,570 -59,57o . Software 10,000 Overheads 7,050 Start-up costs 2,000 i fedac. training 1,500 • 50 Dec Tapes 225 . . Total 87,775 •
2 .9091 70,180 Overheads 7,050 350 3,500 90 180 65 9,750 15 1,125 -046,350 4-142,000 50 Dec Tapes 225 PO Training 2,000
3 .82614 70,130 Overheads 7,050 350 3,500 90 180 65 9,750 15 1,125 +43,575 +140,200
4 .7513 70,180 Overheads 7,050 350 3,500 90 180 65 9,750 1.5 1,125 448,525 +36,600
5 .6830 70,330 Overheads 7,050 350 3,500 90 180 65 9,750 15 1,125 +48,575 +33,200
113,200 +92,430 £108,200 = .9091x + .8264x + .7513x + .6830x + .6209x
3.7907x = 108,200
x = £108,200 3.7907
= £28,600
Assume 255 working days in the year. Assume that the graphics display will be used only during normal working hours, but that with staggered hours these extend over 10 hours per day. The hourly charge for the use of the
equipment is:
£28,600 255 x 10
Or £11.20 per hour.
104 Using this hourly rate the costs for some of the other projects were estimated albeit with less precision than in the case of PCBs. It was estimated that the average accommodation drawing could be performed in two hours using graphics at a total cost (including EA for labour) of £26.
This compared with £28 using manual methods. The cost of producing the logic diagrams, which cost £55 by manual methods, was thought likely to be £1L, consisting of A hours computer time plus labour. Because of anticipated changes in technology, the IC designers were more cautious about providing cost estimates (despite a bench-mark exercise) and limited themselves to commenting that:-
1 Graphics would probably cost either the same as or less
than manual methods, taking direct design costs only into
consideration.
2 The automatic checking routines associated with CAD
systems would be of great, though unquantifiable, value.
On the basis of all the costings above it was decided to purchase a
PDP 15 (the exact configuration is given in appendix a ) and Redac software
(listed in appendixD ) for IC and PCB production.
8.4 The Evaluation of PCB and IC Design Automation after one year
In one respect the success of the work has made a quantified assessment difficult. The demand for computer time is such that it has been difficult to find time to perform the bench-mark tests required. To be useful a CAD bench-mark has to be performed using all the options available, for designs that have already been completed manually. When new "live" work is awaiting machine time this is difficult to justify.
105
The allocation of computer time after the first year of operation differs
in one important respect from the project plan, in which it was intended
to allocate almost all prime shift time to PCB design. Between the
inception of the project and the installation of the computer integrated
circuits became more important in telecommunications and a greater
proportion of the prime shift time has been allocated to this work.
Table 6 shows details of computer utilization during a typical 5 month
period (August-December 1974). In a typical month about 50% of machine
time is allocated to PCB work, about 25% to IC design work, about 17% to
other projects and about 8% is idle. The table also shows the amount of
use outside normal working hours, and shows that the computer installation
is profitable with respect to the internal project accounting system. If
one assumes that the financial judgement of individual research project
managers is sound, this is a good indication that the installation is also
profitable in real terms.
SUMMARY OF PDP15 USAGE 1ST AUGUST TO 31ST DECEMBER 1974
Charges % PCB % MOS OFF PEAK MONTH % Idle £ TO DATE HRS USED
AUG 2518 8 51 18 59
SEP 2437 7.3 44 21 70
OCT 3712 2.3 48 24 97
NOV 3176 8.5 49 24 8o
DEC 2672 17 51 24 53
Annual sum to be recovered £32773
Monthly equivalent £ 2731
Table 6
106 Since it was recognised that the benefits of CAD for IC design, although real, are difficult to quantify, it has been impossible to do an "after the event" DCF that compares directly with the original . It is, however, informative to compare the anticipated and achieved costings for the
design of individual boards. All use of the computer is paid for and the current rates, which include all repayments on capital at 10% over
five years are as follows.
Prime shift raw computer time £12 per hour
Prime shift, major software packages E7 per hour
(These figures assume a,60%/40% distribution of time between the PCB and IC
packages respectively).
Off peak rates are 50% of prime shift rates. The prime shift rate is
calculated so as to recover the basic charges. The percentage rate for
off peak use is a rather arbitrary figure, set to encourage the use of
time that would otherwise be wasted. It is intended to use the "profit"
from off-peak use to reduce the prime shift charges for the subsequent
year. If a decision to operate a regular late shift was made the lower
rate would then apply to all use. The charge for raw computer time
corresponds closely to that calculated originally (Z11.20), which in days
of high inflation is noteworthy. It is due to a fall, in both actual and
real monetory terms, of the price of the hardware. £61,000 was spent
compared with £67,000 that was budgeted.
For Printed Circuit Board design, the economics are as follows.
The amount paid for PCB software increased from an estimate of 210,000
to £28,000 actually spent. There were three reasons for this substantial
increase.
107 1 A decision had been made to purchase a software package that included
facilities for the design of multi-layer boards. At the time of the
original estimate no multi-layer boards had been produced but their
eventual use was foreseen and it transpired that there were commercial
advantages in purchasing both duuble and multi-layer programs together.
In addition, the multi-layer design program included some facilities (in
particular the automatic routing of tracks of varying widths) which would
be useful for the design of two-layer boards. Assuming that the
anticipated multi-layer load materialises this decision improves the long
term profitability of the project at the expense of adverse cash flow in
the early stages.
2 There was a change in pricing policy by the supplier which derived
from the peculiar nature of software. Unlike most other products the
marginal cost of supplying a copy of a program is negligible. The software
house must maintain sufficient revenue to sustain his current activities
and to finance his development work. Its pricing policy (and it should be
emphasised that this has been found to apply to several software houses and not just to the supplier in question) is thus based on market and cash
flow considerations and prices change more rapidly than those of hardware.
This makes long term planning which involves the purchase of software
difficult.
The allocation of time to IC design, noted above, adversely affected the
PCB work in two ways. The number of boards produced annually was reduced
and, subtly, the cost of producing boards by CAD was increased. Hardware
costs to the PCB project (ie for computer time) were reduced linearly to
compensate for the reduced usage. Charges for the PCB package, which was
of no use to the IC designers, could not be reduced pro rata. The PCB
108 % Differences MANUAL COMPUTER between CAD & MANUAL
Time Time Total Total Observed Corrected Labour: Labour: Cost Cost Cost Cost Cost Cos Board Cost Labour: Labour. Comp Comp HRS Observed Corrected @ @ Hours @ @ & £ Observed Corrected Time @ @ Cost Cost Time £18 ph £9 ph £18 ph £9 ph £18 ph £9 ph. )nnections Hrs Hrs Hrs £ £ Hrs £ £ £ £ 96. A 88 175 41.5 36.3 91 79.5 11.5 10 180 90 259 169 41 148 495
B 52 103 22.5 19.7 48 42 4.25 3.81 68.5 34.25 110.5 76 38 107 74 131
C 56 115 24.25 21.4 56 49 5.75 5.04 91.0 45.5 140 94 38 122 81 160
D NA NA 36.5 32 72.4 63 14 12.2 220 110 283 173 NA NA NA 602 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9
TABLE 7 (Calculations to slide rule accuracy) designers had to recover their software costs over a reduced period and consequently their costs were higher than had been anticipated. From a technical point of view, the fact that the installation could readily be switched from PCB to IC design as the latter assumed greater importance is a testimonial to its flexibility. We see a conflict between the demands of rigorous accountancy practice and the realities of a dynamic research environment. An advocate of rigorous costing policy might argue that the IC design should be costed and, if less profitable than PCB design, should not be allocated time. However, the strategic importance of IC design to a telecommunications authority is such that it was a sound decision to allocate time for that work.
In the bench-mark results (appendix E) the observed results are set out.
The multi-layer package, with its improved facilities for routing multi- width racks, could not be bench-marked in time for inclusion in this thesis and the drawing office staff anticipated further improvements in efficiency due to minor modifications to the equipment layout, the software, and to their working practice. These, it was estimated, would produce a 122% reduction in both computer time and in man-hours at the screen. An abstract of figures from the bench-marks is given in table 7.
Explanation of Table 7
Column 1 gives the designation of the board and the number of connections between the pins of components.
Column 2 is the man hours taken to design the board by manual methods.
Column 3 is the cost of the manual design.
Column 4 is the man hours required to design the board using the computer graphics system as it was at the time of the bench-marks.
110 Column 5 is an estimate of the man-hours that will be required to design the board using the slightly improved computer graphics system due to be implemented. The figures are 122% less than those in column 4.
Column 6 is the actual labour cost of designing the board by computer graphics.
Column 7 is an estimate of the labour costs using the slightly improved computer graphics system. The figures are 122% less than those in column 6.
Column 8 is the actual computer time used for the computer graphics design.
Column 9 is an estimate of.the computer time using the slightly improved system and is 122% less than column 8.
Column 10 is the cost of the computer time in column 9 charged at £18 per hour.
Column 11 is the cost of the computer time in column 9 charged at £9 per hour.
Column 12 is the total cost of the computer graphics design if the computer is charged at £18 per hour. ie column 7 (labour) plus column 10 (computer charge).
Column 13 is the total cost of the computer graphics design if the computer is charged at £9 per hour. ie column 7 (labour) plus column 11 (computer charge)..
Column 11 is the man hours required for the computer graphics design expressed as a percentage of those required for the manual design (column 5 column 2 x 100).
Column 15 is the total cost of the computer graphics design (computer time charged at £18 per hour) expressed as a percentage of the cost of the manual design (column 12 ÷ column 3 x 100).
111 Column 16 is the total cost of the computer graphis design (computer time charged at £9 per hour) expressed as a percentage of the cost of a manual design (column 13 4- column 3 x 100).
In interpreting these results the small size of the sample (4 boards) is recognised. As these bench—marks took
112 about 120 man hours to obtain and cost about £800, the cost of a larger sample would be prohibitive. As the boards were chosen with care as being typical, it is thought that results give a good indication of the likely efficiency of the CAD system despite the small sample size. Board C has
76 discrete components and only 6 DILICS. Although PCB designs of this type are declining in number, a board with many discrete components and irregular track patterns was included because this type is regarded a difficult for CAD systems.
Looking at boards A, B, and D all with many DILICS, we note that board A, chronologically the first, was a poor result for CAD and is not consistent with the other two. Although no manual results are available for board D, it contains 22% more connections on the same area and cost only 2%
(@ £9 ph) and 9% (at £18 ph) more than board A. Usually costs rise sharply with the density of the connections and one might have expected it to cost
30-40% more. The CAD costs for boards B, C and D seem consistent with each other and it seems reasonable to assume that the draughtsmen were still gaining efficiency when board A was designed, although their own assessment was that they were fully proficient. We see that -
1 The man hours needed for a computer design are 40% of those
taken by manual designers. This means that, provided time is
available on the CAD system when required, there is a reduction
in delay of about 1 week with respect to the Drawing Office.
The production of artwork on the plotter by-passes several stages
of the photographic process and this results in a further saving
of one week so that thedelay for urgent jobs is reduced by
about two weeks overall. This conclusion is valid for all boards
including the one with many discrete components.
113 2 If only prime shift computer time is used (a conservative assumption) the direct costs would be about 7% greater than by hand, based on the result for "typical" DILIC board B. Costs for boards with many discrete components such as board C can be up to 22% more expensive although the reduction in man hours and lead time is still obtained.
3 If the computer is run for 80 hours per week then, from table 73 savings of about 25% are obtained for the DILIC boards, and about 20% for the discrete component board.
4 The partial evidence provided by board D and by the strong conviction of the draughtsmen is that somewhat greater savings are achievable on large boards with many DILICS.
So far, no allowance has been made for the fact that an 80 hour week implies overtime or shift allowances for the operator.
Although in a labour intensive situations, such payments are expensive this is not the case with CAD. Only the actual design process (not the data preparation) would be done in overtime and an increase of say 25% to the labour cost of a draughtsman for overtime on a 5 hour design session would only add about £2.50 to the costs. The value of the computer time saved would be t45.
If one quotes 25% as the overall saving on a job mix that includes the larger size of board..allowance for overtime and shift payments will have been made. In the opinion of the author, this figure of
25% saving in direct costs is a fair indication of savings obtainable in most engineering organisations.
114 These figures are dominated by computer costs, which are likely to remain
constant for the next five years, since the equipment has already been
purchased. The costs of manual design are dominated by labour rates and
will be subject to whatever inflation occurs. We see that the design time
at the screen, originally estimated at 4 hours for a typical board was actually
3.81 forb and 5.04 for C ,showing the estimate to be approximately correct.
The time actually required for data preparation and verification was 8 hrs.
instead of an estimated 1 hour. However, these figures are not directly
comparable since we see from appendix B (Draughtsman's comments) that the
bench-mark figures include the entering of all component details. As more
jobs are completed a component library will be built up which reduces this
8 hours. It seems unlikely that the estimate of one hour will be achieved
and the eventual result of about 4 hours is likely. As the Mist junior grade
of drawing office labour is involved the cost of this under—estimate is not likely to be serious, (say V( per board) but it is interesting to investigate
the discrepancy. Since the original estimate of data preparation
costs was based on a bench-mark exercise it is surprising that the error was made. When live boards are designed immense care is taken to see that the
data is entered correctly and verification by duplicated data entry is
carried out. It can only be assumed that the bench-mark operators were less
careful than a draughtsman working on live work. Before leaving the subject
of PCB costings it is useful to recapitulate the original assumptions.
These were —
1 The flat bed plotter time was provided free of charge because its
cost had been charged to IC production.
2 Graphics time had been taken from PCB design to meet the
unforeseen demands of IC production.
115 It is instructive to consider the economics of PCB production for a company without the complication of the IC design work. Such a company would not
purchase the Integrated Circuit software but would have the expense of a flat bed plotter. If we associate the cost of the plotter with the cost
of using the computer, which is valid because the plotting time is less than the screen design time, and if we ignore the small overheads
considered in section 1, the calculation is as follows. (1974 cash value
used here).
Computer £65,000
PCB Software £30,000
Flat bed plotter £50,000
Total £1451000
116 Annual charge to recover over 5 years is 150,000 3.7348 (from discount
tables) or £38,824. The hourly rate at 80 hours per week, 52 weeks per
year is then £9.33 per hour. This figure is close to that calculated
for two shift working in the PO application and the implication is that
the gains and losses of integrating IC work with PCB work approximately
cancelled themselves out.
An organisation whose average PCB board is close to bench mark C (131
connections) and whalcan fully utilise its computer by producing 1091 PCBs
per year will reduce its PCB production charges by £29X1091 or £31664.
(These approximate calculations ignore the slight difference between the
hourly rate of £9.33 calculated above and that of £9.00 used in the Post
Office case). The break even point is about 500 boards per year or about
10 boards per week. Thus we can deduce that computer graphics for the design
of PCBs by this method is profitable, but only for the larger organisations.
Non Quantifiable Effects of the Automation of PCB Production
AppendixE lists the Drawing Office comments made soon after the introduction
of the equipment. Although a number of points are raised, the majority are
about details, general reaction to the equipment was favourable.
It is also significant that at a follow-up meeting held with the Drawing Office
some months later, less weight was placed on items such as data preparation
improvement, implying that the learning process took months rather than
weeks. Many of the apparent difficulties could be circumvented as the
designer gained experience. Particular points to be noted are listed
below.
117 1 Over-time, shift working or "flextime" is desirable in order to obtain the maximum benefits of computerisation. The willingness of the staff to
accept this will vary according to the exact arrangements proposed and will
also vary from individual to individual. Care should be taken over this
point.
2 Draughtsmen took readily to the use of the graphics screen for
designing purposes. The ease with which they learnt to load and use the operating system varied from individual to individual, since many had had
no computer experience whatever and it was not economic to employ a full time computer operator to do these tasks. To overcome the problem
additional training in the concepts of computer programs and operating
systems was given. The author has no doubt that this is more practical than
attempting to teach operators the considerable design skills necessary to
design PCBs.
3 The installation of the computer affected many processes further down the production line. At the start of the project only a few boards used
plated through holes and these were contracted out. The automatic track routing programs, whose use was essential to obtain the maximum benefit from CAD, made extensive use of plated through holes. The equipment needed to plate through was ordered but the quality of hole required for this process meant using a high speed drilling head. The provision of this equipment would probably have taken place in any case but the provision of the CAD facilities affected its timing.
4 The equipment met the requirements for R&D PCBs, which was its main purpose. When considering boards for mass production two problems were encountered. It was the practice of some designers to write on the edges of the artwork negative text relating to the circuit. This was not easily
118 handled by the CAD equipment but there was no reason why an alternative method of storing the information could not be found. Secondly some boards intended for production had text relating to the circuit printed on the circuit area by silk screen methods. This could not easily be done using the program because of limitations on the length of text strings. There are no fundamental reasons why a CAD system should not provide for both these requirements.
5 It was found at the outset that some engineers continued to specify features such as rounded corners which could not be handled by the equipment and which were not required for circuit reasons. Such items improved the appearance of the board and had cost little in the days of manual design.
Publicity was necessary to make engineers aware of the increased cost of such requests under the new system.
6 It was observed that on some occasions draughtsmenwould use a light pen in order to improve the appearance of a board that, from a circuit point of view, had already been completed by the automatic routines.
Although not strictly in accordance with the objectives of cost minimisation the fact that the system allowed this was an asset since it contributed to the designer's job satisfaction. This is, perhaps, a good example of the managerial technique of job enrichment.
7 Between 90 and 99% of the signal tracks were routed automatically.
8 An example of the importance of the CAD system's reduced production delay was soon encountered. A high priority project was running several weeks late because of delays in the production of printed circuit boards.
Using the graphics system three 10" x 7" PCBs each with 1,000 connections were produced at the rate of.1 per week to bring the project back on
119 schedule. It was noted that these boards were about as large as the system could easily handle, but larger boards were not likely to be encountered because the 10" by 7" dimensions were the largest allowed in standard equipment racks.
INTEGRATED CIRCUIT DESIGN
A summary of the software purchased is given in appendixD . Because the labour involved in producing and checking IC masks is large, and because of changing technologies, a detailed cost comparison of the IC mask application is not possible. Instead the performance of the designers when working on a selected job was monitored. This job was a 512 bit random access memory.
A large part of the silicon area consisted of a single pattern. Although not typical of previous jobs it was thought likely to be representative of future projects involving the design of microprocessors. Graphics were used for two task-, These are detailed in paragraphs (1) and (2) below. Figure 1j. shows a typical integrated circuit produced by the P.O.
120 ------
Read only memory circuit
121 Neg. RES. 19344 1. To construct the decoder and the input/output stages. In each
case a single unit was designed on graph paper and the graphics used
to repeat the unit 8 times to form larger sub-units.
2. To form the main memory matrix of 512 bits which is composed of
16 rows of 32 bits. One cell was designed on graph paper. This was
digitised and the graphics used to repeat the cell 512 times.
The system constructed the items in 1 above in a satisfactory manner. However,
for item 2 the core store became full when one horizontal row of 32 cells
was completed. This meant that the data had to be transferred onto disc
(a 3 minute operation) and when this was done the "Group Code" and origin
were lost. This problem was tackled by making one complete row a library
item and calling it up to repeat rows - this task took about 8 hours on
the screen.
Also, sub-units containing a lot of data could not be moved on the screen.
Hence it was difficult to interconnect sub-units on the screen to complete
the layout. As a result of these problems a number of improvements were
suggested by the IC designers.
a. Software Change to Prevent Loss of Groups
A portion of the layout, for example a standard logic cell, can be
described as a Group. A Group can be defined in an operating
window but the Group definition is lost when the operating window
is changed. This means that one cannot return to the original
window once it is changed and, say, adjust the original position
of the Group.
An alteration to the software to prevent this loss of Group definition
when changing the operating window would be helpful.
122 h. An incroPse in the Size of the Display File
An increase in the size of the display file would offer two advantages.
First it would he possible to get more layout data in the operating
window. This would save time as fewer operating windows would be
required to cover the chip. At present it is necessary to transfer
data from a disc to the core store when changing the operating wirdow•—
a process which takes several minutes.
Secondly, if more of the core store was allocated to the display window
(this is a part of the operating window) it would be possible to construct
a more complex layout in the display window. In the present system a
layout can be built up in the display window but when the complexity
reaches a. certain level the core store becomes full and the progrPm automaticall:
windows to a smaller area. This can take several minutes due to disc trans- fers. c. Group Outline Facility
An alternative approach to help overcome the limitations of the core store
would be to build a complete Group and then reduce the amount of data in
a Group by entering a routine which dumps all the information except for
a 101Lm wide border. This silhouette could be moved as a Group on
the screen. The final operation would be to re-enter the data into the
area contained by the perimeter.
d. Improvement in Digitising Language
It would be useful if the graphics digitising language offered some of the
facilities of GAIT; in particular the ability to repeat Groups in the
x and y directions and also the rotation of Groups through multiples of
90°.
123 a. Impravere'lts to 'lindo,r 7olitine
Practical restrictions on the size of the display window used in
particular operations, for example 3roup and Rxtend, mean that the display
'window must be changed to complete the operation. At present this operation
is difficult and it would be helpful if the Window routine was a subroutine
of the other routines.
f. The chip size using the graphics is limited to 4000 x 4000 units and if 1 unit equals 1 IA. the chip size is restricted to 4mm x 4mm. This was too small for some circuits being considered.
Previously the layout rules had used . units - of 2/44t; this gave a
maximum chip size of 8mm x 8mm
g. Lines which are not horizontal or vertical cannot be accommodated.
It WS noticed that an increased packing density can sometimes be obtained
by using angled lines.
124 Changes in technology were seen as likely to produce problems. A shift from
silicon to metal gate MOS technology was anticipated shortly afterwards.
The design programs could cater for this but the checking programs could
not. Other technologies such as bipolar (which has circular areas) were
thought likely to pose problems.
The above list of deficiencies may appear considerable. Nonetheless the use
of the graphics equipment was popular with the IC designers and during the
first year of operation a lack of computer time was the limiting factor.
The initial reaction was to modify the software but this proved difficult
mainly because of hardware limitations on the PDP 15. Although core store
in access of 32 K could be added it had to be accessed by indirect
addressing techniques. It was not easy to make that part of the data
structure in the directly addressable core compatible and interchangeable
with the part in indirectly addressed core.
In the event two things mitigated the deficiencies of the software. Items
'relating solely to the ease of use,such as window changes , although far
from ideal were found to be manageable as the designers gained experience.
It was found possible to merge parts of the circuit designed on the graphics
equipment with CAMP compilations at the plotting stage. This made the
interconnection of large chips easier than using the graphics alone.
Finally on topics such as the checking of metal gate MOS further programming
was undertaken.
One hardware problem was encountered. The equipment initially relied upon
paper tape transfer between the computer and the plotter. Even with a
high speed paper tape punch this process could take several hours and was
vulnerable to even the most transient computer fault. It was decided to
125 replace the paper tape reader on the plotter with magnetic tape, and it was shown that the computer time saved would justify the expense (£14,000).
RECENT DEVELOPMENTS IN COMPUTER GRAPHICS a. Storage Tubes
17" tubes are now available and the cost has fallen to £4000 for a terminal and hardcopy unit. b. Refreshed Graphic Systems
Ostensibly the price of graphics equipment has fallen, and several apparently low priced display units are now available. On closer examination of the price lists we see that two things have happened
Genuinely cheaper units are now available but these have small screens, and limited character and vector generation facilities. Their prices range from £10,000 to £20,000. These displays will find economic applications in industry but, for the applications reviewed in this thesis they fall between two stools. They are three or four times the price of the storage tube that meets the requirements of graph plotting, and yet suffer from the very limitations of screen size, and total vector length that became crucial when large and complex ICs and PCBs are drawn.
Other displays offer a large screen and make adequate provision for vector and character generation. The crt and control electronics cost about
£20,000, and this has changed little over the last four years. However, systems in this category, have been the beneficiaries of a spectacular drop in the price of small computers. Displays which ten years ago would have required central processors like the ICL 4200 or IBM 1130, costing upwards of £70,000, can now be supported by processors such as the PDP 11/40
126 costing about £20,000. The addition of peripherals adds to the cost but a practical refreshed graphics configuration can be purchased for about
£50,000. c. Automatic Drawing Systems
These systems have undergone continuous development in recent years and now hold a dominant market position especially, for the design of ICs. Their major components are a digitising drawing board capable of mounting a full sized engineering drawing, a digital plotter (which in some cases is combined with the digitiser), a small computer, a small graphics screen
(often a storage tube) and a graphical tablet or joystick. Many systems originate in companies with close contacts with the semiconductor industry, and the software provided relates closely to the user's needs. This "turn key" approach has led to their success, rather than the engineering features of their systems. Ingenuity has been displayed in the implementation of intractive facilities but ergonomically even the best do not compete with the large screen refreshed graphics systems. The automatic drawing systems cost between E35,000 and £65,000. d. Laser Systems
One system is now marketed in the UK and has two modes of operation. The main mode is a storage mode, in which the light beam is used to mark a diazo film. The image of this is projected onto a im minscreen. The resolution is such that an immense amount of data can be stored.
The second mode is a direct view mode in which the laser beam, suitably attenuated by darkened mirrors, is deflected directly onto the screen.
In the absence of an electron activated phosphor only the natural retentivity of the eye is available to give the impression of continuous
127 vision. This means the length of refreshed vectors is limited to about 9
inches and has the distinctive shimmering appearance of coherent light
sources. The equipment is very large and costs about £45,000. As
components in IC design schemes where absolute ease of use outweighs cost,
laser displays probably have a future but only very specialised companies
will be able to afford them.
e. Published Work on the Economics of Graphics
During the period of this investigation, as previously, very little
information has been published. In 1974 the author was asked by the IEE
professional group committee C5 to organise a seminar on "The economics
and practical aspects of using computer aids for the design of printed
and integrated circuits"(56). Despite much effort no authors could be found who gave detailed cost figures although much useful information
on the 'practical aspects' was obtained. The continuing lack of
published information is due in part to commercial security but there is
a dearth of tabulated costing information on graphics topics.
(50) Hookins and Emms quoted figures of between £3 and £4 per package for
a totally automatic routing scheme. Direct cost comparison on this
basis is difficult but their costs seem slightly lower than those
achieved by the PO refreshed graphics for a restricted range of boards.
(The system described handled only logic boards of standard sizes).
DeMari(51) included very general figures for one PCB benchmark in his
paper "System Design at Fiat's Computer Aided Design Laboratory" which
were favourable to computer methods. Zelinger(52) published a paper
entitled "On Line Interactive Graphics - The Designer's Dream or the
Production Manager's Nightmare" which emphasised the cost benefits of
128 Computer Aided Production rather than design. The figures quoted seemed to be based on hypothetical study rather than case histories but Zelinger is correct to highlight the uneasy relationship that can exist between the design and production functions within a company. f. Recent Developments in Software Relevant to Graphics
In view of the conclusions drawn above relating to the importance of software some recent developments in the field are of interest.NEDLANI the (2110 generalised network program technique devised by Marovac, should if widely adopted make the implementation of all network type of programs cheaper. These would include not.only the "obvious" networks such as circuit diagrams and PERT charts but also PCB and IC layouts.
Although primarily concerned with 3D representations, and thus slightly peripheral to the main subjects of this thesis, the Gino package(25 ,) because of its availability on a bureau basis through the CAD Centre at Cambridge is likely to prove a useful tool.
g. Fully Integrated Design Schemes
A number of the large IC manufacturers have implemented their own fully integrated CAD schemes. These schemes are seldom published in detail but their components are described below. There is a medium size computer, which because these schemes develop over a number of years, is often of an older generation. There are usually facilities for both digitiser and direct screen input. The software usually includes programs for logic simulation, graphical display, dimensional checking, error correction, diagram generation and ATE program generation. In some cases there are programs to check that the IC cells produced match the original Boolean specification. A feature of all systems is a unified data file structure
129 which acts as a link between the programs. This is particularly important
as the tedious and error prone data entry operation is only performed once.
h. IC Design Using Storage Tube Terminals
The GAELIC program(34), which combines the facilities of CAMP with the
somewhat limited interactive facilities of a storage tube terminal, has
advanced considerably and now includes checking programs. Without more
detailed evaluation the author is unable to decide whether programs of
this type should be regarded as a replacement for refreshed graphics in
IC design or as a useful addition to them and at present feels inclined
towards the latter view.
GAELIC has a well organised data structure and with some adaptation could
provide, by means of a storage tube terminal, a low cost, low precision
automatic draw i_ng system. It could well prove suitable for several of
the applications considered in Section 3.
.10 PROGRESS ON APPLICATIONS OTHER THAN PCBS AND ICS
The PCB, IC and graph plotting work described above absorbed most of the
resources available for computer graphics during the past three years.
The other applications described in Section 3 were also considered and
the current state of each is given below.
a. Graphical Pert. A general interest in the topic continues,
especially with respect to the design of stored program control telephone
exchanges. GAELIC and NEDLAN are thought to have potential here.
b. Machine Shop Scheduling. The graphical approach has been abandoned,
and the practicality of even conventional scheduling programs is in
serious doubt.
130/ 131 c. Accommodation Plans, Computer Assisted Drawing and Decision Networks.
Interest in these applications continues, with storage tubes and an
adaptation of the GAELIC program being considered for these jobs.
d. Flow Charts and Coding for SPC Telephone Exchanges. The automatic
generation of coding is still regarded as desirable in the long term but
present effort is devoted to the generation of flow charts and bar charts
for documentation and project control.
e. On Line Production of Spectrograms. A direct hardware solution was
found for these problems. This did not involve computer graphics.
f. The Legibility of Alphanumeric Characters. This problem assumed
greater importance due to projects such as CEEFAX(54 ). ORACLE(55) and
VIEWDATA(60,) which require the presentation of alphanumeric characters on
domestic TV screens. Computer based experiments were used in these
investigations but a raster scan display, refreshed directly from core
'store was used rather than other types as this corresponded more closely
to the proposed final system.
g. Models of Transistors. Interest in this topic has increased but
conventional computerised techniques are being used at present.
h. Thin Film Technology Circuits. The demand for this type of circuit
was the subject of a further survey of users and proved to be insufficient
to justify the deployment of CAD resources.
i. Text Editing. Interest continues in this subject but simple
alphanumeric displays are being used because they are cheaper.
132 11 CONCLUSIONS
The prime objective of this work was to investigate the application of known computing techniques in industrial research. Nonetheless certain features of the CUPID project are, as far as can be ascertained from published work, original. In particular the use of an interpretive graphical command processor linked to the data files of a general scientific operating system is thought to be novel. Most previous work in thig field has used sub- routines compiled with the application program. Interpretive techniques have been used on dedicated local computers but the graphical commands were incorporated within a special language and were difficult to apply to data generated by programs written in other languages. The CUPID philosophy-offers a very high degree of interaction combined with complete flexibility regarding data sources. The resultant package is versatile and easy to use. The extracts from the CUPID log, printed in Appendix A and analysed in section 7 , contain detailed information on user behaviour at a graphics terminal and should prove of value to those implementing interactive graph plotting packages in the future. On the hardware side our users' experience with CUPID demonstrate the adequacy of the direct view storage tube terminal used over the public switched telephone network for this type of work, and confirmed the crucial importance of hardcopy.
Regarding the application of existing techniques the initial survey confirmed that the potential uses in the field of electronics and its related constructional technologies are many, with graph plotting4curve fitting,
PCB and IC design,and technical documentation predominant. It also revealed that apart from technical problems a variety of human attitudes were extremely important. Considerable research has been carried out by
Mumford and others on the human problems encountered when data processing computers are installed, but these problems have been neglected in
133 industrial scientific environments. The author contends that a knowledge of the attitudes described in section 2 is crucial to the success of any scientific computing project affecting a spectrum of users. Early and continuing contact with the end user is essential. It should also be noted that, particularly in the case of PCB production, the introduction of
CAD techniques produced effects much farther down the production chain than had originally been foreseen so everybody involved in the production process should be consulted, as well as designers.
On the matter of costs it must first be stated that the task of
gathering enough accurate information to draw conclusions with the
degree of confidence normally required by both scientists and
accountants proved more difficult than was anticipated. This is
partly because it is dependent on controlled benchmark experiments
which are themselves expensive and partly because technologies
change within the costing period. The chief technological
change encountered was an increase in the importance of ICs,
which the graphics system easily handled, thus providing
evidence of its intrinsic flexibility.
The DCFs show that both graph plotting and PCB production should
prove economic in the cases described. They also show that, in
the general case, graph plotting is economic for an organisation
producing at least 2 complex graphs per working day and that PCB
production is likely to be economic for an organisation producing
on average 2 PCBs per working day. On the basis of these figures
only the larger electronics research organisations can justify their
own equipment although many others might find the occasional use
of CAD bureaux economic. (Bureaux facilities are now available for
both remote storage tubes and refreshed graphics).
134 One tentative calculation places the number of PCBs (designs and major modifications) by British Industry at 40,000 per year. This is equal to the capacity of 50 installations similar to that described above but, since in practice the boards are located in diverse companies and locations, there are probably only about 20 or 30 UK organisations, public and private, for whom automated PCB production would be profitable.
IC mask production proved harder to cost but graphics was regarded as a valuable addition to their tool kit by the designers, despite the fact that changes in technology limited the benefits obtainable. Because the cost of CAD equipment is small compared with production equipment, and because the error checking programs are valued highly, most organisations concerned with IC production are likely to consider graphics in one form or another worthwhile.
The falling cost of hardware is sometimes presented as presaging a major breakthrough in the exploitation of computer graphics. This falling cost is indeed a welcome bonus to the economics of graph plotting, PCB design and IC design and could also be crucial in applications such as circuit design and technical documentation. However, for PCBs, ICs and graph plotting software costs dominated the DCFs This situation may cause those implementing graphics projects in industry to choose obsolescent hardware because it is provided with good working software. This is a situation similar to that encountered by EDP systems designers in the late 1960s.
To summarise: for electronic engineering applications computer graphics can be profitably exploited and has developed beyond the stage of computing science research. It remains somewhat expensive and until there is a major breakthrough on the reduction of costs, particularly software cost, its economic deployment will be limited to the larger research organisations.
135 APPEIDIX P.: A 7,0G OF CUPID CO!IlAJ:D USAG s AUD THE CUPID COMUPJID riDEX
A REPRODUCTION OF THE CUPID LOG SHOWING COMMAND USAGE - RECORD OF USAGE
PRINTED: 11.30 30 Jun 72 USAGE SINCE 22 MAR 72 NO OF TIMES USED = 257
TOTAL CONNECT TIME = 56 HRS 58 MINS 27 SECS TOTAL CPU TIME = 1 HR 18 MINS 52 SECS RATIO (CPU/CONNECT) = 1.38 MINS/HR
COMMANDS—FREQUENCY OF USE
XAXIS 33 XAXIS 28 XINC 151 YINC 7149 XSPAN 2A0 YSPAN 193 TEXT 228 ALIGN 0 XGRID 6 YGRID 9 GRID 34 DUMP 1,03 LOAD 508 PLOT 2339 FRAME 16 XAMOT 7 YANOT 2 DATA 535 DRAW 23 PYE 264 XTIC 20 YTIC 20 LINE 180 SYME 167 COPY 9 RETI 4 ERASE 51 MOVE 35 MODE 34 CANCE 58 RESET 110 STAT 61 'AXES 62 TICS 40 ANOT 24 PTS 14 XFORM 52 YFORM 48 FORM 22 WINDO 197 PIC 142 FIT 260 REMOV 133 REFIT 17 COEFF' 139 LIST 144 CHEAT 51 COLS 43 ITEMS 8 FROM 34 CLEAR 0 BLOCK 2 HIST 30 KEY 12 ***** 3 AUTO 31 DELET 9. RES 18 SMOOT 248 TIME 9 RUN 54 SNO07, 197 WAIT 4 SPAD 15 HARD 0 EDIT 24 AXSHI 73
136 PRINTED: 17:33 33-APR-73
NO. OF TIMES USED = 679
TOTAL CONNECT TIME = 121 HRS 5 MINS 55 SECS
TOTAL CPU TIME 3 HRS 13 MINS 59 SECS
RATIO (CPU/CONNECT)= 1.56 MINS/HR
COMMANDS - FaEQUENCY OF USE
XAXIS 165 YAXIS 158 XINC 315 YINC 311 X3PAN 431 YSPAN 537 TEXT 105/. ALIGN 3 X3RID 61 YGRID 52 GRID 218 DUMP 163 LOAD 369 PLOT 3575 FRAME _ 39 XANOT 13 YANOT 7 DATA 1577 DRAW 53 BYE 679 XTIC 20 YTIC 12 LINE 478 SYM3 402 COPY 7 RETUR 0 ERASE 243 MOVE 112 MODE 4 CANOE 229 RESET 311 STAT 31 AXES 42 TICS 45 ANOT 23 PTS- 11 XFOTI 51 YFORA 63 FORA 28 WINDO 231 PIO 114 FIT 347 REMOV 71 REFIT 4 COEFF 65 LIST 105 CREAT 597 - COLS 493 ITEMS 473 FROM 551 CLEAR 1 BLOCK 1 HIST 38 KEY 21 VERSI 6 AUTO 23 DELET 5S RES 6 GRAPH 85 TIME 6 RUN 31 SNOOZ 0 WAIT 7 SPAD 38 HARDC 16 EDIT 0' AXSHI 19 PAGE 0 DEVIC 0 XFIT 1 MERGE 33 SMOOT 129 XEAR 53 YEAR 15
137 •'0UPID' - fizanD OF USAGE.
PIINTED: 11:51 23-4UJ-73
USA 3E SINCE 31-MAY-73
NO. OF TINES USED = 65
TOTAL CO'1JECT TIME = 7 'IRS 51 :INS 1 SECS
TOTAL CPU TINE 0 MIS 13 NINS 19 SECS
RATIO (CPU/COANECT)= 2.23 NINS/NR
CONAANDS - FREQUENCY OF USE
:''AXIS 3 YAXIS 25 XINC 45 YINC. 49 :',SPAN 44 - YS7AN 51 TEXT 16/4 ALIGN ri ' 138 CUPI - iiFroin) ()v.- PAINIEO: 2-AUG-73 USAGE SINCE 28-JUN-73 NO. OF TIMES USED = 99 TOTAL CONNECT TIME = 2.6 HiIS 23 'INS 7 SECS TOTAL CPU TIME = 0 HRS 24 MINS 8 SECS RATIO (CPU/CONNECT)= 0.90 •MINS/HR COMMANDS - FREOUENCY OF USE XAXIS 25 YAXIS 62. XINC 55 YIVC 65 XSPAN 110 YSPAN 100 TEXT pqm ALIGN n XGIID 6 YGRID 6 GRID 37 DUMP 4h LOAD 98 PLOT 628. FRAME 2- XAVOT ci YANOT 2 DATA 280 DRAY 3 BYE 99 XTIC 2. YTI c o LINE 66 SYMR - 82 COPY 0 RFIUR 9 ERASE 35 - MOVE 3 MODE . .0 CANCF 187 RESET 90 STAT- 11 AXES -.5 TICS . 5 AVOT 0 .PTS 1 XFORM 16 YFORM 11 FORM :1 WIND° 17 PIC 18 FIT 167 REMOV 40 REFIT 1 COEFF 62 LIST 2n6 GREAT 249 COLS 226 ITEMS 52 FROM 177 CLEAR 0 BLOCK 0 HIST 0 KEY 3 VERSI 1 AUTO 0 DELET 1 RES I.' GRAPH 5. TIME 1 am 0 SNOOZ 0 WAIT 0 SPAD 3 HARDC 22 EDIT 0 AXS4I 2 PAGE 0 DEVIC 0 XFIT 0 MERGE 0 SMOOT 13 Xi3AR 7 YBAR, 2 .;139 CtT1-11. rP C311....) F 7-ZIi/TE7: 11: - 2-OCT-73 •'./SAG 5 I :1 C::. 31- AiI5 - 73 `10. OF T.I:LI:S USEO = 111 TO7A% C0.1:!ZOT TL1E = 15 :17:S 32 :;INS 43 SECS' TOTAL C')U TIME = 1 11711 25 AIN'S 33 SECS n.ATIO CC7311/C0:LIZCT)= 1.52 NIUS/H11 CO:11A7D3 - FT:EWE:ICY OF USE 11.:f S ,7) Y A.0 I S 11 7:I1C 51 YL/ C 1 9 ::.31, P,:; 12", 73''c I 31 T7:7 116 ALI Gj ':01I D 3 5 YG71ID 5 G71I D 30 DUL.i? ' 35 LOAD 50 PLOT 431.— FRiVIE 13 7:ALJOT 2 .Y11:!07 1 DATA 172 DnAv . 13 ,.my-7 _ -Z.7 I C 111 5 . "TIC 6 LINZ 61 57i13 33 CO27 9 RETUT1 1 EnASE 35 my": ':ODE 21 1 . C:13 OE 37 7E3E7 15 STAT 2 A":,--21 2 TI CS 1 1110T 13 .?TS '7 1 0 :II 7 YFO '1:1 •5 F07.1 /I UINDO ''IC 11 FIT 22 7ZA01.7 2 REF 1T CO EFF 0 2 LIST' 13 CilEAT COLS 2 I T;:.:1S 2 Imo: ; 3 CLEAT: 3 =ILO C: 9 :LI 3T 1 NE7 5 VE71S I 1 AUTO 2 D2LET 7 air s o GRA?;1 2 TE/E 1 71U4 1 S:1001 I ':IAI T 1 f SPAD 17 :i11'? 7C -3 - 1:.1D1 T 1 XtS11I 4 PAO!: 15 rEn:I/ 39 ':FIT 2. :IsaGE 2 5.4100T :!.?,A7). '3 Y5A1 '3 IO r'33.:41'i•.:.): 1 A: rt3 31- 0 CT - a USAGE SINCE .270CT-73 H NO. OF TIMES USED = 195. 'FOTAL CONNECT TImE = 24 HAS 0 MINS 51 SECS TOTAL CPU TIE 1 HRS 3 MINS an SECS RATIO C CPU/CONNECT )= 2.64 rNS/HR COMMANDS - FREQUENCY OF USE z cv: 1 s - 7 Y A.( I S 31 KI)JC R5 Y NC R1 KSPA.N 96 YSP AN 143 TEXT 191 ALI GV 1 XGRI D 8 Y(:I D 8 G P. I D - 61 DUMP /42 LOAD 110 PLOT 726 FRAME 9. XANOT n YANOT 9 DAT A 343 DR A r., 5 1:1YE 195 XII C 0 YTI C .. 9 LINE A7 SYMII - 41 COPY 0 RETUR 0 -.RASE 65 MOVE, 5 MODE 0 CARE - 24 il E.S ET 96 STAT 1 A:(ES 15 TI CS n •60J0t 1 PTS lt X F 0 ii:•1 11 YFORM 6 FOP, 0 :.; IN DO 63 PI C 14 FIT 134 !? F. ,19k) -54 REFIT 1 CO FEE 9 LIST R MEAT RP COLS - . R1 I TEAS 71 Fi,10:1 70 CLEAR 2 BLOCK n HI ST 9 KEY.. S ti P' P,S I I AUTO 7 0 RFS 0 GRAPH 0 TIMF n /TMIR.INJ 0 SNOT?: 0 i.,i AI T 0 SPAD 6 i4ARDC 0 EDIT. 0 AKS HI 0 PAGE 7 TERM' 6 KEIT 0 MERGE 0 SMOOT i 0 - XBAR 5 YBAR 0 141 - io.rrpn OF 1 (-*.A(z*p 11:56 9-DFC 73 lo. OF TIelf.S USuD = 17R TOUAL CO■14YCT riNIF = 27 4PS A6 MI\IS 29 SVGS f01161. CPI' n 1-1r!S 4r4 MI VC 17 SYCS qAFIO (CP1'/C040('F)= IiAg MIgS/u0 COvIAAVOS - FRI4W1•\MY OF ITSF /AXIS . 24 . YAXIS - • AP XI \IC A7 YT VC 4r1 ASPAq 11W! YSPAV 123 11.7:T 3A4 ALTC\I " ',GRID 1/1 YPPTD 11* Srtn . 79 WM? 11 0 LOAD 25A PLOT n2 F9ANIF- q ' !,CA\IOT 1 YA4OT -9 DAIA 172 npAw . . 5 1 rlyF 17q. XFIC . S• YTIC . 3 LTV. =0 Symn SQ CONE 9 • RETtIP rl 1 P.ASF RI mOV F /.1= MODE • 2 •CANICE pc PFSFr Ws STAT in A.Y. .6 TICS 4 A1OT i PIS A XFOP1 - 6 YFOH'1 Pi FOPm 1 *VI\Ing 1 1-- PIC 9 FIT 95 Rt.10V 1A pFFIT n COFFF 31 LLsr iS C1?F 0 T - Al COLS 17 Irl.ms 34 FRO'! Ah .CLFAP 9 : ru,orx IA HISr 13 KFY cf VPSI 9 A:1 T9. 1 t)1-CJf .19 P.T.S A (;Pap4 1 TimF 1 PAN 6 SVO0f, 79 waIT 9 SPAT). 1 HA! A; 34 FDIT 1 AKSLIT PAC;F A 1- 0- 1I igK9 .FIT • 9 MF9PF 1 SMOOT on! XPAR YWAR P .142 - 1-- L1_ , PRINTED: 17:45 F76-0-74_ USAGE SINCE :::-DEr-774. rm. OF TIMES USED = 419 TOTAL CONNECT TIME = 57 HRS 11 MINS 11. SECS TOTAL CPU TIME =. 2 HRS 40 MINS 2 SECS RATIO COMMANDS - FREQUENCY OF USE XAXIS 26 ?AXIS 45 XIHC 191 YINC 168 XSFAN 279 YSPAN Ri.. TEXT 50::: ALIGN 0 XGRID *20 YGPID 18 GRID 82 DUMP 191 259 PLOT 1415 PRAME 4 XANOT 8 =g-r- 8 DATA 614 DRAW 24 BYE 419 XTIC 54 YTIC 38 LINE 299 SYMP. 125 COPY 0 RETUR 0 ERASE 172 MOVE 13 MODE 4 CANCE 118 RESET STAT 7 AXES 5 TICS 11 ANOT 2 PTS 5 XFORM 72 YFORM 77 FORM 2 WINDO . n PIC 31 FIT 128 RENO V 51 REFIT R .COEFF 51 LIST 31 CREPT 137 COLS 101 ITEMS 1:740 FROM 122 CLEAR 2 BLOCK 0 HIST 0 KEY 11 VERSI 2 AUTO 0 DELET 10 RES ,.., GRAPH R TIME S' RUN SHOOS 1 WAIT •0 SPAD 40 HARDC 46 EDIT 0 AXSHI ,c PAGE 12 TERMI 59 XFIT 0 MERGE ....L_.D SMOOT 42 %--.:cc. 10 YEAR 0 143 'CUPID' - RECORD OF USAGE PRINTED: 11:25 1 MAR 7i. USAGE SINCE 14 FEB 714 NO. OF TINES USED = 156 TOTAL CONNECT TINE = 20 HRS 32 MINS 36 SECS TOTAL CPU Tfl = 0 HRS 51 MINS 44 SECS RATIO (CPU/CONNECT) 2.46 MINS/HR COMMANDS - FREQUENCY OF USE XAXIS 13 YAXIS 36 XINC 84 YINC 57 XSPAN 96 /SPAN 87 TEXT 267 ALIGN 0 XGRID 0 YGRID 2 GRID 36 DUMP 52 LOAD 77 PLOT 591 FRAME 2 XANOT 3 YANOT 2 DATA 359 DRAW 0 BYE 156 XTIC 8 YTIC 9 LINE 86 SYME 59 CORY 0 RETUR 0 ERASE 83 MOVE 7 MODE 0 CANCE 137 RESET 140 STAT 33 AXES 21 TICS 3 ANOT 3 PTS 0 XF'ORl•t 25 YFORM 23 FORM 2 WINDO 3 PIC 8 FIT 61 REMOV 15 REFIT 5 COEFF 39 LIST 44 CREAT 59 COLS 49 ITEMS 7 FROM 52 CLEAR 0 BLOCK 11 HIST 5 KEY 0 VERSI 0 AUTO 13 DELET 3 RES 0 GRAPH 2 TIME 0 RUN 0 SNOOZ 0 WAIT 0 SPAD 17 HARDC 8 EDIT 0 AISHI 5 PAGE 0 TERMI 28 IFIT 1 MERGE 0 SMOOT 0 IBAR 5 YEAR 0 • 'CUPID' - RECORD OF USAGE PPINTEL.: 17:41 4-APR-74 U:AGE SINCE 1-MAR-74 HD. OF TIME: U:ED = 143 TOTAL CONNECT TIME = 20 HR.: 31 MINS 17 SECS TOTAL CPU TINE 0 HRS 42- MINS 57 SECS RATIO (CFU,CONNECT)= 2.04 MINS/HR CONNANDS - FREQUENCY OF I.Y.7'E XAXIS 4 YAIS 37 XINC. SF, 94 YSPAN 120 TEXT 294 ;:li_NN. 6: 1 .YGRID 1 GRID 34 DUMP 72 PLOT. 509 FRAME 3 XANOT 5 YANDT 0 - DATA 2::15 DRAW 0 DYE 143 FII 6 YTIC 7 LINE 70 SYMD 64 COPY 0 RETUR 0 ERASE 70 MOVE 0 MODE 0 CANOE 37 RESET 35 'STU ,_.m.. AXES F. TICS 1 ANOT 0 PTS 0 XFORM 28 YFORM 7:0 FORM 13 WINDO 0 PIC '•L. FIT 34 REMOV 6 REFIT 0 COEFF 9 LIST 11 CREAT 68 COLS 60 ITEMS 22 FROM 49 CLEAR 1 BLOCK 0 HIST 0 KEY 2 VERSI 2 AUTO 1 DELET 0 RES 1 GRAPH 0 TIME 0 RUN 0 SNOT? 0 WAIT 0 SPAD ,_., HARK 0 EDIT it AXSHI 0 PAGE- 2 TERMI. 15 XFIT 0 MERGE 0 -SMOOT 2 XDAR 0 YEAR 0 145 CUPID - RECORD OF USAGE PRINTED: 09:47 30-APR-74 USAGE SINCE 4-APR-74 NO . OF TINES USE) = 11 Q1 TOTAL CONNECT TINE = 19 HRS 42 MDIS 2 SECS . TOTAL CPU TINE 0 HRS 51 MINS 49 SECS RATIO ( CPU/CONNECT) = 2.58 MINS/HR. COMMANDS - FREQUENCY OF USE XAXIS 8 YAXIS 7 XINC 41 I1NC 43 %SPAN h5 YSPAN 75 TEXT 2)43 ALIGN 0 XGRID 5 YGRID 5 GRID 20 DUMP 51 LOAD 121 PLOT 482 FRAME 3 XANOT 3 YANOT 0 DATA 219 DRAW 5 BYE 110 XTIC 7 /TIC 2 LINE 38 SYM3 29 COPY 0 RETUR 0 ERASE 103 MOVE 14 MODE 0 CANCE 24 RESET 87 STAT 3 AXES 3 TICS 0 ANOT 1 PT S 0 X.P3RM 7 !FORM 7 FORM 0 WINDO 13 PIG 5 FIT 7 REMOV 1 REFIT 0 CO EFF 7 LIST 29 GREAT 129 COLS 97 ITEMS 79 FROM 85 CLEAR 0 BLOCK 0 HIST 0 KEY 1 VERSI 0 AUTO 0 DE1,ET 1 RES 0 GRAPH 0 TIME 1 RUN 0 SNOOZ 0 WAIT 0 SPAD 8 HARDC 12 EDIT 0 AXSHI 0 PAGE 0 TERMI 8 XFIT 0 MERGE 0 SMOOT 0 %BAR 0 YEAR 0 SIZE 2 PETS 0 INC 0 ROTAT 0 146 CUPID - COMMAND INDEX AND QUICK REFERENCE For more detail refer to the CUPID Command Manual(56)° COMMAND PARAMETERS FUNCTION ALIGN H Align text horizontally or vertically V ANOT none Control printing or non-printing of ON axis annotation OFF AUTO none Forces CUPID to scan data and set its AXES axis limits or annotation format FORMAT AXES none Controls type of axis (linear, log or ON square root) and whether or not the OFF axes should be drawn LIN LOG SQRT BLOCK none Block text horizontally or vertically BYE none Causes exit from CUPID CANCEL file Removes file from list of data files to be plotted. CLEAR none Resets FROM, COLS and ITEMS parameters to their default values. COEFFS none Displays coefficients of least squares polynomial COLS Xcol,Ycol Specifies columns from which X and Y data are to be extracted COPY text spec Copies a string from one position to another CREATE file Creates a file containing a subset of some other file DATA file Adds file to the list of files to be plotted DELETE none Deletes vectors inserted by DRAW no.of vec- tors DRAW none Draws vectors on the screen DUMP file Dumps the picture information for subsequent recovery ERASE none Erase a piece of text 147 COMMAND PARAMI.TERS FUNCTION FIT deg.of poly Fits a least squares polynomial FORMAT format spec. Determines the format in which axis annotation is printed FRAME none Determines printing or non-printing ON of picture frame OFF FROM file File from which data subsets are to be created GRID none Specifies grid lines at axis increments ON OFF no.of sub- divisions HARDCOPY none Triggers hard copy unit HIST none Specifies that data should he plotted ON as a histogram OFF NOLINF ITEMS start Items within columns from data subsets start,inc are to be created start,inc,end KEY file Create a data file from the keyboard LINE ON Type of line which joins data points OFF CONT DASH DOT CHAIN LIST none Display contents of file file LOAD file Load picture information from previously DUMPed file MERGE filel,file2,file3 Create a file by merging two other files in order of ascending X MODE text spec. Change style of text MOVE none Move a piece of text text spec. PICTURE none Set size and position of Picture frame SQUARE PLOT none Plot the current data file OVER 148 CONI.: Ai 1) PARAMETERS FUAiGTIGii POINTS none Plot or suppress plotting of data points ON OFF REFIT deg.of poly Fit polynomial and remove last one RENOVE, deg.of poly Remove polynomial from those to be plotted TES lncr. -Set increment for polynomial evaluation And smoothing .RESET -none Reset system and restore presumed settings :RETURN -none .Return to user prorram RUN .Run stored commands in file £MOCTh none interpolate between data points ON OFF deg.of smooth SNOOZE :none Temporarily suspend processinr ma.of secs SP -none Switch between screen and scratch-pad ON for commands OFF STATUS none Disilay list of data files set with LINE, DATA SYMBOL,RIST and SLOOTH information POLY SYLOL OFF Specifies symbol used to rare each data POINT point CROSS STAR SQR TRIG CIRCLE TEXT none Insert a piece of text text spec. TICS none Specifies tic marks at axis increments ON OFF no.of sub- divisions TIME none Display total connect and CPU time WAIT none Suspend processing until operator restarts 149 COKIYAND PARAPET FUNCTION WINDOW none Zoom in or zoom out on displayed nicture EXACT SHUT XBAR none Display data as vertical bars ON OFF width of bar YRAR none Display data as horizontal bars ON OFF width of bar XqRID none As for GRID ON OFF no.of sub- divisions XINC axis incr. Set size of X axis increment XSPAN xmin,xmax Range of X axis values XTIC none As for TICS ON OFF no.of sub- divisions XFIT xmin,xmax Range over which polynomials will be evaluated XFORMAT format spec. As for FORMAT. YGRID YINC YSPAN As for X command above YT IC YFORMAT I .150 The following options are set on initial entry to CUPID or after RESET command has been given:- ANOT ON AUTO AXES AUTO FORMAT AXES ON AXES LIN FRAME ON GRID OFF MODE HUS POINTS ON RES 10 TICS 1 The following options are set each time DATA is used:- LINE ON SYMBOL OFF HIST OFF SMOOTH OFF 150a APPENDIX int - CUPID cormund lanruage syntax 151 APPENDIX C HARDWARE CONFIGURATION OF THE REFRESHED GRAPHICS COMPUTER The refreshed graphics system consists of the following hardware:- PDP15/76 computer with 32K words of core memory. UC15 unichannel - PDP11j05 with 8K words of core memory (for control of peripherals). Memory multiplexor. GT15 graphics terminal. LA30 DEC writer TU56 dual DEC tape drive. RK05 exchangeable disc drive [14M words (18 bit) capacity]. PC15 paper tape reader/punch (reads at 300 chs per sec and punches at 50 chs per sec). LV11 Versatek electrostatic printer/plotter (in character mode 500 lines per min, 132 chs per line and in plot mode 122,880 dots per sec). PDP15 Facit 4070 paper tape punch (75 chs per sec). Figure 1 is a photograph of this equipment. Figure 2 is a photograph of the Ferranti flatbed plotter used to produce artwork and masks. Figure 3 is a close-up of the screen when being used for IC design. 152 I. eansTa 3 xialudav APPENDIX C ricure 2 154 Appendix C Figure 3 155 APPENDIX D PROGRAMS FOR THE LAYOUT OF INTEGRATED CIRCUITS AND PRINTED CIRCUITS INTRODUCTION REDAL is a suite of programs using an on-line CRT display to aid in the layout of integrated circuits and printed circuits. On completion of layout, paper tapes may be produced for driving a Ferranti flat-bed plotter. These programs were written by Redac Software Ltd. INTEGRATED CIRCUIT LAYOUT - METHOD OF USE The sequence of programs used to layout and produce masks for M.O.S. and Bipolar Integrated Circuits is shown below:- REDAL CIRCUIT CODING REDAL 1 V CIRCUIT LAYOUT. DESIGNER INTERACTION REDAL 5 V ERROR CHECKING REDAL 6C Nie ARTWORK DRAWINGS 156 INTEGRATED CIRCUIT PROGRAMS - METHOD OF USE (Continued) PROGRAM FUNCTION COMMENTS Redal 4 To simplify the The input data may be prepared in one of 'INPLAN' inputting of data two ways:- to the graphic 1. Manual method - The circuit is coded Layout data system software. manually by reading off co-ordinate points preparation from the circuit diagram and incorporating program. Input to the them in the appropriate 'Redal 4' program is a paper description statement. tape which contains a numer- ical description of the circuit. Output from the 2. Digitizer Method - A faster method program is stored of extracting the co-ordinate data from on disc or the circuit diagram is to use Ferranti magnetic tape and Free Scan Digitizer. The output from this is in a form would be run through a conversion program compatible with to produce 'Redal 4' type statements. the graphics system software. Redal 1 Displays the This is the design stage and operates 'LADYJANE' data produced interactively. The design may be modified by Redal 4 on the by adding or deleting shapes or Layout Aid V.D.U. manipulating shapes already existing. on Graphic Circuit design experience is required to Display Operation is now operate this part of the system. interactive using a light pen and menu type approach. Input is the tape or dis0 file produced by Redal 1. A copy of the final circuit description may be stored on paper tape or mag- tape. 157 PROGRAM FUNCTION COMMENTS Redal 5 Checks topology of The user specifies the separations of the laid out circuit various features of the circuit that he Dimensional against a set of requires checking. checking design rules Circuit design experience would be program specified by the required to interpret the error listing user. produced. Input is the tape containing the circuit descrip- tion produced by Redal 1 together with a paper tape containing the design rules. Output is a line- printer listing of the errors giving the X, Y co- ordinate of the errors together with an indication of the type of error. Redal 6c. Post processor to The program operates in 2 modes. produce a paper Data conversion 1. Normal mode - A tape of the whole of tape in a format for Ferranti the selected layer is produced. suitable for flat-bed driving a Ferranti 2. Repeat mode - Any faulty tapes plotter. plotter. Input is produced in the normal mode can be the circuit descrip reprocessed. -tion produced by Redal 1. This is a straightforward job to produce a plotting tape. The job is a purely mechanical operation taking only a few minutes. 158 INTEGRATED CIRCUIT LAYOUT PROGRAMS - SUMMARY DF MAJOR ROUTINES REDAL 4 Circuits are coded numerically using 5 types of statement. 1 Shape statement - Defines a shape and gives it a name. 2 Group statement - Defines a set of shapes as a group. 3 Recalled statement - Reproduces a previously named shape or group at a different reference point. 4 Macro Reproduce statement - Generates a -succession of similar shapes or groups equidistant from each other. 5 End of Data statement - End of data indicated by *. REDAL 1 'LADYJANE' The program operates on up -4)15 layers on an area initially 4000 units square. The interactive facilities available are - 1 Shapes may be manipulated ie transposed and rotated. 2 Further shapes may be added. 3 Shapes may be deleted. 4 Groups of shapes may be defined. 5 Any particular layer may be made brighter than the rest. 6 Small areas of the picture may be magnified for closer examination. REDAL 5 The features on the circuit that may be checked are 1 All items be within the defined bounds of the chip. 2 Minimum item width on each of 15 layers. 3 Minimum item separation on each of 15 layers. 4 Diffusion - to diffusion separation on transistor gates. 5 Contact window to diffusion separation. 6 Contact window to thin-oxide separation. 7 Contact window to aluminium separation. 8 Gate - thin oxide overlap to drain and source diffusions. 159 9 Gate - aluminium overlap to gate-thin-oxide at drain and source diffusions. 10 Gate - aluminium overlap to channel sides. 11 Diffusion to unassociated thin oxide separation. PRINTED CIRCUIT BOARD PROGRAMS - METHOD OF USE A sequence of 4 programs is used to layout printed circuit boards. The circuits may contain discrete components, integrated circuits or a mixture of the two. The boards may be single sided or double sided. The table below describes the function of each of these programs. 140 PEDAL 7 CIRCUIT COCINC AND VALIDITY CHECKING PEDAL 3 •■■•■ warms. •■•■••• •••■••• .1••■••• AUTOMATIC IDESIGNER PLACP,1ENT INTERACTION I < I AND ROUTING L- ••■••••• 01.71.M •••■•■ SMIMMIND •■••! REGAL 7 PEDAL 8 ART'u7OPK., DRAWINGS N.C. DRILLING 161 PROGRAM FUNCTION COMMENTS Circuit Coding. Data for input to The circuit designer supplies a circuit Redal 3 is pre- diagram on which is shown aLl components pared on paper together with their values and inter- tape. connections. Note Two sets of From this the data prep offf_cer extracts data are prepared the following information for the paper independently if tape. checking with 1. List of component outlimes. Redal 7 is 2. Location of component connections required. within these outlines. 3. Component list. 4. Connection list. 5. Statement of board shape and size. This work involves engineering and D.O. knowledge, and a familiarity- with the symbols specified in BS 393. Redal 7 Redal 7 operates Input to the program is two nieces of paper (mode 1) in 2 modes. Its tape and the output is a lineprinter Error detection function here is listing of any errors detected program. to check the The data prep officers check and correct validity of the their work. They may have tp call on the initial data. assistance of the circuit designer if It does this by design errors are suspected. comparing two independently prepared sets of data. Redal 3 or Displays the data This is the design stage and would be Redal 14 on the VDU. operated interactively from she graphics Initially all terminal. Layout of Printed Circuit components are Boards. 162 PROGRAM FUNCTION COMMENTS placed in a heap a. In the case of low frequency circuits, at the origin. The D.O. staff, who are already doing this system is now work using manual methods, would be interactive and the ideally placed to use the graphics user has at his terminal after a short period of training. disposal a series of routines which b. In the case of very complex and novel enable him to place circuits, the circuit designers inter- the components on vention may be required. the board and man- Note When making connections using ipulate the conn- Redal 3 the designer must distinguish ections for minimum between power and signal tracks. track length and minimum number of crossovers. The finished design may be output to paper tape. Redal 7 The function here The data prep officers concerned would (mode 2) is to compare the again interpret the error listing and Error completed layout make the necessary corrections. At this detection with the initial stage a copy of the finished layout would data. be sent to the circuit designer for his approval. Redal 8 Converts The operator inputs Redal paper tape and Post processor information collects plotter tape. This operation program produced by is purely mechanical and only takes a Redal 3 into a few minutes. paper tape suitable for driving 1. Ferranti plotter 2. N.C. drilling machine 153 PRINTED CIRCUIT BOARD LAYOUT - SUMMARY OF MAJOR ROUTINES INPUT DATA The input data is prepared in the following form. 1 Library List - This list consists of a statement of each component shape to be used, together with the X and Y co-ordinates of all the connections within that shape and a number identifier for each shape. Pad sizes are specified for each connection. 2 Component List - All components including test points and edge connectors etc. are listed. Each component is given a name eg R3, C14 followed by the identifier from the library list. 3 Connection List - A list of all connections taken from the circuit diagram in the form:- R2 1 C3 2 Statement of Board Size - This states the X and Y co-ordinates of all corners of the board. REDAL 3 This program is interactive and the routines available include:- 1 MOVE - components may be moved, rotated, fixed and unfixed. 2 WINDOW - A small area of the circuit may be magnified for closer examination. 3 ROUTE - Connections may be replaced by routes. Routes can also be deleted. 4 MODIFY - The original data may be modified eg further components may be added. 5 PLACE - Gives an initial guide to the best layout automatically. 6 AUTOROUT - Automatic, semi-automatic and manual routines for minimising crossovers. 7 RECONN - Sorts connection trees for minimum connection length. 8 MANHAT - Places routes automatically taking into account pad size and track widths. 164- REDAL 14 "AUTO" This program performs similar functions to Redal 3, but allows for Multilayer PCBs. In addition it gives the designer additional routing options, in particular the ability to distinguish between tracks of different widths. This is particularly important when power rails are being positioned. A comparison of facilities between Auto and Redal 3 is included, because this is important when analysing the benchmark results tabulated in Appendix E• 165 THE FACILITIES OF REAL 3 REDAL 14 FACILITY REOAL3 REDAL1 Multilayer Boards No Yes Routing without plated Yes through holes Pre-routing manually No Ties Specifying the side, lies or layer for a route Max No. of segments 5 I 32 per -route Automatic Routing of tracks of specified Yes widths only Moving components lirithout its routes Yes I No being replaced by connections Manipulation of groups Yes I No of components Renaming of Yes I No components 166 1 APPENDIX E PART 1 Benchmark Designs and Results, for the Evaluation of the P.C.B Automation. BOARD A NO OF CONNECTIONS = 495 COMPONENTS = 32 DIL's + 42 RESISTORS + 15 CAPACITORS BOARD SIZE = 10.0" x 7.8" Shown in Plate 1 of Appendix E BOARD B NO OF CONECTIONS = 131 COMPONENTS = 10 DIL's + 7 RESISTORS t 1 CHOKE BOARD SIZE = 6.5" x 7.5" Shown in Plate 2 of Appendix E BOARD C NO OF CONNECTIONS = 160 COMPONENTS = 6 DIL's + 28 RESISTORS + 28 DIODES + 20 TRANSISTORS BOARD SIZE = 5.5" x 5.5" Shown in Plate 3 of Appendix E BOARD D NO OF CONNECTIONS = 602 COMPONENTS = DIL's + 78 RESISTORS + 11 CAPS BOARD SIZE = 10.0"x 7.8" Shown in Plate 4 of Appendix E 167 3 COITARATIE COSTIMS BOARD A CAD LABOUR COMPUTER Grade Cost Grade Cost Graphics Stage B C Time (Hrs) (E) (Hrs) (E) (Hrs) Data 12.00 20.62 Prep Data 2.58 0.50 Checking 1.50 Design > 8.0 33.26 15.00 25.77 10.00 Post 1.00 1.72 1.00 Processors Artwork Production 4.00 6.87 & Checking ( Totals 8.0 33.26 33.50 57.56 11.50 Man Hours - 41.50 Computer time = 11.5 hours MANUAL 1 ■ DO DO DO DO Photographer's Grade Cost Grade Cost B C Cost (c) (Hrs) (E) (Hrs) (E) 8.0 33.26 80.0 137.W. h Man Hours = 88.0 x Cost = £174.70 168 •• DSEXA 0 .1:1 1 9 1 8 I LT t° I 1 4 4 • 17::'r7; 9 a 4949499 •I °•••11 4. . : ri / IT u713, 4 4 4 4 • , d 2 4■,. 4 a •-4,°_°Y I • 1919999 I r 6 e• =.1.0 • • 11f1lt=1110000 111.°L1, • :7:71 4 4944 •• ••••1 1... 0000 i p--0 9 i114 I • 9°9 I 4 99 .11°.", r 17.. • ...LT] 0-d .1111 • 1 O 9 99 •••••••11 99 °*".°11 00 00 "1111 " H0I3FWAY CARD A LCP23 R 15 47 0 (X721 • e e • O •• • I. IP Plate 1 Board I. 169 COMPARATIVE COSTIEGS BOARDS- B CAD LABOUR COMPUTER Grade Grade Graphics Stage B Cost C Cost time (Hrs) ( 0 (Hrs) (0 (Hrs) Data 8.00 Prep 13.74 Data Checking 0.25 0.43 0.25 Design > 4 16.63 7.00 12.03 3.50 Post Processors 0.50. 0.86 0.50 Artwork Production 2.50 4.30 & Checking t Totals 4 16.63 18.25 31.36 4.25 I Man Hours = 22.25 Computer Time = 4.25 hours MANUAL Grade Grade B Cost Cost Photographer's (fir s) (0 (Hrs) (Z) Cost (L) 4 16.63 48 82.46 4 I Man Hours . 52 Cost = £103 170 DSEXB 0 •10 0000 1 000 0000 - 917 1 100400° p000do 000 000 000 0001,000 000 •0?0 000 •0?0 0.. 0:4° COUNT AND STORE 0 8 X 2 ° 110000 el•e•e„ 10 0 0 011 010 00 00 00 000 100001 I 0400T000- 00;0 • 0 0 0 0 0704400 0 1 0 "'plate, 2 Board B 171 AHATI`TE COSTINGS .BOARD C rAD IABOUR COMPUTER Grade Graphics Grade Cast Cost . :Stage - B G -tine (Hrs ) (..t) (Hrs ) (E) (Hrs ) :Data :8 - If rep "1:3.714 data C.25 Checking :0:25 0.143- Design 6 214.94 7.00 -1 2..03 :5;00 :Post '0 .50 'Processors - 10;50 0.186 _Artwork Production :2 ;50 4.30 e.... Checking :Totals 6 24.94 18.25 31.36 5.75 .Man Hours =241.25 Computer Tine = -5.75 hours MANUAL 1 Grade Cost Grade Cost That ographer 1 s C Cost ( £ ) (Hrs) (E) (Hrs) (L) 6 24.94 50 85.90 _4 _I Man Hours = 56 Cost £1311.811 172 DSEXC 0 1.1.1. 1, irmsm „ 1101° T-T 0 0 0 0 0 0 0 0 0 0.0ii00 0000000 010100 . . 110 2 17,77.- "SATE AU BOARD 3 RS 3 2 0 0 0 OX320 0 ... 11111110 00 100 00 T-11 ee. gr-111 00 14 II 00 prl OO l'r—f :F.1 0 1:0 °i1 10 :1 :1 0 1: t;;;;ill:E__T: 10 00 00. II II" , !I III 0 0 Plate 3 Board C 173 .LABOUR COMPUTER Grade Cost Grade Cost Graphics .Stage B C time (Hrs) (Z) (Hrs) (I) (Hrs) Data 10.00 17.18 Prep . Data # 1.00 1.72 0..50 checking Design 11.0 16.63 16.00 27.49 12.00 Post P rocessors 1..50 2.56 1.50 .Artwork • Production .4.00 6.87 & Checking totals 4.0 1.6.63 32.50 35.82 114.00 o4 Man Hours = 36.5 .computer time = 14 hours No Manual results are available for board D. 174 PC002 1 ..4. .11 —Ws-4 .1 111.ra-21 , trrr 1 kJ • ..... 1...6... Ifed.1 —1 :•-•-° I °' 0-----e I • 6-- o .L.1., .. 11°11 1.0•01*. 1.•.•. 0,1 • • I I • • La,' °°°°°°' o • ....6., ..• .• °I .1 •l• `--7° 5-1-r.111.1 Ili I ' • a I•y•-••• !1, ••••-• ._Lsr•-•-••-•• To•••••• o •—• CONTROL CORD LCP 20 R1E, 41 00000 • 1 7'1E3 to 4 Board P 175 DRAWING OFFICE COMMENTS ON THE FACILITIES PROVIDED Listed below are some of the observations that have been made by Drawing office staff while using the PCB design packages. This list is not exhaustive and no attempt has been made to establish priorities for the amendments suggested. DATA PREPARATION he standard assignment table could usefully be revised to provide arrange of-pad, hole, track and edge connector sizes that were Post Office standards. b It would be an advantage if the number of characters per component name were not limited to four. DATA CHECKING a It would be an advantage to be able to check connection lists on, say, the IBM 370/168 since this would lead to a significant reduction in the computer time used by the non graphics utility TTograms on the PDP15/76. b Time could also be saved if the input data to REDAL 7 were on a dectape or disc USE OF THE GRAPHICS SCREEN a It would seem that there is a case for either wending Z ROUTE to include all of the above options available in AUTO ROUTE or alternatively using the multilayer package for designing single and double sided boards. More detailed studies of these two routines from both the operation and software aspects are necessary before drawing any firm conclusions on this matter. 176 b Some people have expressed the need for route corners to have a radius and for as much copper on a board as possible. c The input of data to the layout routines from dectape or disc is required. The facility to change the side of the board displayed on 'the screen and to expand, contract or move -the displayed area whilst in any routine. POST PROCESSORS a IREDAL 12 would seem -to be of little - value but :could be -turnedto some advantage if the co-ordinate values output were of those pin number- one of each component on the board rather -than -the no-ordinates of the reference corner of the :component. b The identification drawing post-processor puts components names in the centre of the component outline. An option to displace the component name from this position would enable the production of silk screen printing masters on the Ferranti Plotter. c There may be a case for the provision of a magnetic tapeunit for the PDP15 and the Ferranti Plotter to reduce the running time for the pcB and MOS post processors. 177 17,7777,17'7r77,0 1 Suther1Pnd, 27 7. A Man Nnchine Graphical Communication System,. M.I.T Lincoln Laboratory Report. T.7.296 Jan 1963. 2 Roberts L G. Machine Pereeption of Three Dimensienal Solids. M.I.T Lincoln Irboratory T2315 Nay 1963. 3 WO 7"1iott and P N Fenwick. 'Progress in low cost grPphics'. Tho Computer - .111etin, Volume 15, No 1, Jan 1971, page 16. 4 G C Barney and J N Hamburg. 'The connection of storage display terminals to a time sharing eomputerv. The Computer Bulletin, Volume 15, No 1, Jan 1971, rage 24. 5 D J Grover. 'Low cost graphic display with serial access store'. The Computer Bulletin, Volume 15, Ne 1, Jan 1971, page 33. 6 T H Myer and I E Sutherland. 'On the design of display processors'. Communications of the ACM, Vol II, page h10, June 1968. 7 D J Myrme. 'Computer Graphics - Part 1 Choosing a System'. Computer Aided Design, Volume 3, No 3, Spring 1971, rage 18. 8 A Van Dam and J C nichener. 'Storage Tube Graphics: a comparison of terminals'. International Symposium Computer Graphics 70. 9 Dovere„ C. Storage Cathode Pay tubes and Circuits. Second Edition March 1970. Tektronix Inc. 10 Rose N A and Oldfield„ Printed Wiring Lavout by Computer. Eleetronics and Power October 1971. 11 Oldfield, J V. The Case for Interactive Computer Graphics. Electronics and Power February 1969. 12 Newman., 117. A Prototype Low Cost Simple User Graphics System. FTP '..lbring Conference on Graphic Lanuar'es VPncover, nay 1972. 13 Trier, P 7. Computer Aided Design in 7lectronic. T77 7lectronicrl Division Chairman's Address October 1971. 14 Ministry of Technclo7y Computer Aided Design Committee. Report on Computer Graphics. January 1969 Fazes 20-23. 15 ThacT7e1 B and' 'borsch U. The Man Conruter Link. A Survey of existf- equipment. E:a Flectronics Ltd July 196P. 16 F Y. Appendices to Graphical Output in a Research Department International SyYTosium Computer Graphics 70 (RCS Multi-Access Group) Jul, 1968. 17 Muriford r, N,;rcer N, Mills S and Weir w. The 7uman problems of comr,lier ir+roduction.Mannoement Decision Vol 10 No 1 Spring 1972. 18 Jenkins A P, and Jones C D. An Interactive Graphical System Using Co7nut-srF linked by n Vo-7 e.Ori—nde Ti_ e.. Tritt-rnPtion,1 Graphics 70, 2runel University. April 1970. 178 19 7-71ntt; T. Co .-,-_ tnr Cr..Thins fnr 7,'a egr-ed Circuit Pe sign. international S,-;-mposium Computer Grrphics 70, PJrunel University Anri71 1970- • 20 Perslop, R D, Grenn, R 7, 2ds. Advanced Computer Grrnhics, 7connmics Techniques rnd Arrlicrtions. Based on Internr.tionr1 qTnnosium, C A. 70, Prunel University April 1970. 21 New mm„ An 77perimentra Progrr.m for Architectural Design- Computer Journal Vol 9, ro 1, ny 1966. 22 newmen, Til: end Sproul, F F Principles of Interective Computer Grephics. nrtgrnw Hill 19Th. 23 Ellis, 70, Heafner, J F and Sibley TIC. The Grail Project. An a 24 rarovrc, Y. Dofining Generrl networks for CAD. Computer Journal Vol 17 ro 4 7ov 1974. Page 332. 25 Tbodsford P A. GT70 - Graphical Input/Output University of Cambridge CAD Group June 1969. 26 Lee, R M. Four Test Prtterns for Vector (line drawing) Computer Displrys. Society for Information Display Journal USA Vol 11, Yo 2, (I!rrch April 197h). 27 Barron D Jnb Control Inngurges end Job Control Promrams. Computer Journal Volume 17 7o 3 August 1974. 29 Silvester, H, Brown C F. A computer Prog.rrm to Produce Steroescopic Vi ewe Of 1-:a.t'aerrtinel unctions. PO Research Memorenda Jrnurry 1971. 29 K H, 7=, H. The Use of the Computer Progrem Suite Orchnrd for Designing the Artwnrk of Double Sided PCP-. The 7nrccni Review Vol XY=II 7o 194 3rd Quarter 1974. 30 Bowden (Lori). Article on the Prrsiliar Peconomy. The Gurrdirn July 9 1974 31 Hewlett; R J. Simplifying Dosimn Finnncirl Tires, Jcnurry 22 1973. 32 Atiyeh J. The Use of Grrrhic Disrl-y ns en Aid to Integrated Circuit Masi; Production. Internetionn? Conference on Computer Aided Design IDE Tmblicfltior No 51, April 1962. 33 700:1 B, E0-, el.. Computer Aided. Production of Yns::s for Silicon Tntegrnted Circuits. Ibid. 179 34 Eades, J D et al. Application of GAELIC to the Design of large scale integrated circuit. International Conference Computer Aided Design. IEE Conference Publication No 111 April 1974. 35 Hillier W E Practical Multilayer Printed Circuit Board Layout Using Interactive Graphics. Ibid. 36 Eades, J D. Graphical Layout of Integrated Circuits. IEE Colloquium on the Economic and Practical Aspects of Using Computer Aides for the Design of Printed and Integrated Circuits. March 1974. IEE Digest No 1974/15. 37 Ramsey, F R. Computer Generation of Artworks for PCB and ICs. Ibid. 38 Cook, D E. The Economics of CAD in PCB Design. Ibid. 39 Neill, T B M. An improved Method of Analysing Non-Linear Networks. International Conference on Computer Aided Design Southampton, April 1969. IEE Conference Publication No 51. 40 Van Dam, A and Evans, D (1967). A compact data structure for storing, retrieving and manipulating line drawings. Proc. SJCC p 601. 41 Proceedings of the 1968 NATO School on Software Engineering. NATO Publication. 42 Repsher, W G. Bellflow Draws Flow Diagrams Automatically. Bell Lab Record Vol 49 No 7 August 1971. 43 Cloot, P L and Sutton-Smith, C N. Management Use of Displays in Critical Path analysis. Computer Graphics in Management-Case Studies in Industrial Applications. K Elliot-Green and R D Parslow (Editors) Gower Press 1970. 44 Nicholson, T A J. A Review of Scheduling Techniques. AERE Harwell Research Memo AERE M1694 1966. 45 Newman,W.E. and SprouliR.F. Principles of Interactive Computer Graphics. Mcgraw Hill 1974 Part 1 pages 1-80. 46 Carmody, Stevens et al. .A Hypertext Editing System for the 360. Pertinant Concepts in Computer Graphics. Faium, M et al (Editors) Urbana III 1969 Pages 291-350. 47 Clarke, K E and Woods, B J. Cupid - An Information Display System which exploits the Characteristics of the DVST. Datafair 1973 BCS Conference Publication. 48 Clarke, K E. Assessing the Performance of Computer Graphics systems. Conference on Computer Performance - Methods of Assessment. University of Surrey, England. Sept 1972. BCS Conference Publication. 180 49 Schlechtendall, E G. A comparison of Integrated Systems for CAD. Computer Aided Design Conference 1974 IEE Conference Publication No 111. 50 Hookins, K H and Emms, H. "The use of the Computer Program Suite ORCHARD for designing the Artwork for Double Sided PCBs. The Marconi Review. Vol XXXVII No 194. 51 De Mari, A. System Design at Fiat's Computer Aided Design Laboratory. Proceedings of the Conference "On-Line 72" p. 619, Vol 2, Sept 1972. 52 Zelinger, S H. On Line Interactive Graphics - The Designer's dream or the production Manager's Nightmare. Ibid. 53 Wise, D J K. LIDO - An Integrated System for Computer Layout and Documentation of Digital Electronics. Computer Aided Design Conference 1969. IEE Publication 51. 54 CEEFAX. BBC Engineering Information Sheet 4008(2) June 1974. 55 ORACLE - Broadcasting the written word IBA Publication 1974. 56 CUPID. Conversational Utility Program for Information Display. Volume II Users Guide. Version 2. 57 Apperley„ M D and Spence, R. Innovation in the Application of Interactive Computer Graphics to Circuit Design. 1974 European Conference on Circuit Theory and Design. IEE Conference Publication No.1160 58 Chasen, S. H. Applications of Man-Computer Graphics. International Symposium on Computer Graphics 70. Brunel University April 1970. 59 Foley, J.D. Optimum Systems Design of Computer Driven Graphics Terminals. International Symposium Computer Graphics 70. Brunel University, April 1970. 60 Fedida, S. VIEWDATA, An Interactive Information Service for The General Public. Eurocomp conference, London 1975. (obtainable from P.O.Research Dept., Martlesham, Suffolk.) 181