with the Generation of
VLSI Design and Implementation Methodologies
by Lynn Conway
Xerox PARC Technical Report VLSI-81-2
Copyright @ 1981,
Lynn Conway. All Rights Reserved.
Also published as:
"The MPC Adventures", by Lynn Conway,
Microprocessing and Microprogramming - The Euromicro Journal, Vol. 10, No.
4, November 1982, pp 209-228.
PDF (20p; 8.0mb)
Editor's note, 1-10-15: In this
report, Lynn described the methods used to deliberately generate the engineering
paradigm shift later known as the "VLSI Revolution". However, being an early
exploration in "social physics", the concepts went completely over the heads of
audiences back in 1981.
ended up simply being taken for granted, and her role in causing the paradigm
shift faded from history. It wasn't until late 2012, when Lynn stepped forward and
published her "VLSI
Reminiscences", that people began to
fathom the depth of what had actually happened
In January 1981,
Lynn Conway gave an invited talk at the
Second Caltech Conference on Very Large Scale Integration. Her
talk provided a sketch of the early
work on VLSI design methodology, and the efforts to test,
debug and propagate the resulting VLSI design methods.
- The talk also described the new form of internet-based MPC
implementation infrastructure conceived of by Lynn Conway, and
architected, developed and implemented into innovative software
and procedural protocols by Conway, Alan Bell and Martin Newell
- The MPC system supported rapid prototyping of many student
design projects at many universities in '79 and '80, and played
an important role in the evaluation and propagation of the Mead-Conway
design methods and design courses. Alan
Bell created a semi-automated e-mail interaction interface for
the MPC software server which enabled a very large scale-up in
the number of users and the amount of interaction with each user. MPC79 was thus one of the earliest demonstrated
forms of automated, internet-based "electronic commerce",
in this case, commerce in VLSI design files and the resulting
- The Mead-Conway methods went on to have considerable
Courses rapidly spread to scores of universities. DARPA initiated
a major VLSI research program to support extensions of their
work. By '82-'83, the courses were being offered at over
110 universities worldwide. The book
eventually sold over 70,000 copies. Many companies were started
to design new VLSI systems and to provide VLSI CAD tools to the
new VLSI designers.
- The MPC technology itself was transferred to USC-ISI in 1981,
where it became known as the "MOSIS"
system. ISI has operated and evolved MOSIS right up until the present time,
with support from NSF and DARPA, as a national infrastructure
for rapid prototyping of VLSI designs by universities and research
- Lynn's 1981 Caltech talk about these events was transcribed
and published as Xerox Palo Alto Research Center Technical Report
VLSI-81-2. This report follows below (you can also retrieve a PDF of the
report at this link: [PDF]
- THE MPC ADVENTURES:
Experiences with the Generation
of VLSI Design and Implementation Methodologies
an Invited Lecture at the
- Second Caltech Conference on Very Large Scale
- January 19,1981
- Lynn Conway
Copyright @ 1981,
Lynn Conway. All Rights Reserved.
PALO ALTO RESEARCH CENTER
3333 Coyote Hill
Road/Palo Alto/California 94304
- During the early '70's, Carver
Mead began a pioneering series of courses in integrated circuit
design at Caltech, presenting the basics of industry MOS design
practice at the time. Observing some of the students' successes
in later doing projects using these basics, Mead sensed that
it might be possible to create new, much simpler methods of IC
design than those then used in industry.
- In the mid 70's, Carver Mead
and Lynn Conway, and their research groups at Caltech and Xerox,
began a collaboration to search for improved, simplified
methods for VLSI system design. They hoped to create methods
that could be very easily learned by digital system designers,
but that would also allow the full architectural potential of
silicon to be realized. Their research yielded important basic
results during '76 and '77. In the summer of '77, they began
writing the textbook Introduction to VLSI Systems, to
document the new methods.
- In the late 70's, Lynn Conway
realized the need for large-scale experimentation to further
generate, test, and validate the methods. Conway began using
novel methods within a systematic, rapidly expanding set of interactions
with many universities throughout the United States. Students
at these schools took courses using the evolving textbook,
and then did design projects as part of those courses.
The projects were implemented, and the resulting feedback was
used to extend, refine, and debug the text, the courses, the
university design environments, and the new design methods.
- As a result of the research
methodology used, and the very large scale of the interactions
with the university community (via computer-communications networks),
the Mead-Conway design methods evolved unusually rapidly, going
from concept to integration within industry in just a few years.
- This talk tells the story of
these events, focussing on the research methods used to generate,
validate, and culturally integrate the Mead-Conway design methods.
- 1. Introduction
- 2. Evolution
of the VLSI Design Courses; Role of the MPC Adventures
MIT '78 VLSI Design Course
MPC Adventures: MPC79 and MPC580
- 3. Present
Status of the VLSI Design Courses and the VLSI Implementation
- 4. Sketch
of and Reflections on the Research Methods Used
- 5. Looking
- 6. Acknowledgements
- 7. References
- 8. Suggested
- It's great to be here with you today.
I remember an equally sunny January day here in Pasadena when
the first VLSI Conference was held at Caltech two years ago.
That seems such a short while ago, but the period since has been
one of tremendous activity in VLSI, a time of real discovery
and rapid progress. I'm really looking forward to the Technical
Sessions of the next two days, to hearing about some of the best
recent work in this exciting field.
- My talk today is about "The
MPC Adventures", namely the multi-university, MultiProject
Chip escapades of the past two years. I'll describe these adventures,
and the new VLSI implementation system that made possible the
economical, fast-turnaround implementation of VLSI design projects
on such a large scale. I'll also describe the experiences I've
had with the processes involved in generating new cultural forms
such as the "Mead-Conway" VLSI design and implementation
methodologies. One of my objectives today is to help you visualize
the role that the "MPC Adventures" played in the generation
of the methodologies.
- I am particularly interested
in developing effective research methodologies in the sciences
of the artificial, especially in areas such as engineering design.
The sort of question that really interests me is: How can we
best organize to create, validate, and culturally integrate new
design methods in new technologies? What are the research dynamics
involved? Consider the following:
- When new design methods are
introduced in any technology, especially in a new technology,
a large- scale exploratory application of the methods by many
designers is necessary in order to test and validate the methods.
A lot of effort must be expended by a lot of people, struggling
to create many different systems, in. order to debug the primitives
and composition rules of the methodology and their interaction
with the underlying technology. A similar effort must also be
expended to generate enough design examples to evaluate the architectural
possibilities of the design methods and the technology. That
is the first point: A lot of exploratory usage is necessary
to debug and evaluate new design methods. The more explorers.
that are involved in this process, and the better they are able
to communicate, the faster the process runs to any given degree
- Suppose some new design methods
have been used and fairly well debugged by a community of exploratory
designers, and have proven very useful. Now consider the following
question: How can you take methods that are new, methods that
are not in common use and therefore perhaps considered unsound
methods, and turn them into sound methods? In other
words, how can you cause the cultural integration of the
new methods, so that the average designer feels comfortable using
the methods, considers such usage to be part of their normal
duties, and works hard to correctly use the methods? Such cultural
integration requires a major shift in technical viewpoints by
many, many individual designers. Changes in design practices
usually require changes in the social organization in which the
designer functions. These are difficult obstacles to overcome.
We see that numbers are important again, leading us to the second
point: A lot of usage is necessary to enable sufficient individual
viewpoint shifts and social organization shifts to occur to effect
the cultural integration of the methods. The more designers
involved in using the new methods, and the better they are able
to communicate with each other, the faster the process of cultural
- When methods are new and are
still considered unsound, it is usually impossible in traditional
environments to recruit and organize the large numbers of participants
required for rapid, thorough exploration and for cultural integration.
Therefore, new design methods normally evolve via rather ad hoc,
undirected processes of cultural diffusion through dispersed,
loosely connected groups of practitioners, over relatively long
periods of time. (Think, for example of the effect of the vacuum
tube-to-transistor technology transition on the design practices
of the electronic design community, or of the effect of the discrete-
transistor-to-TTL technology transition). When the underlying
technology changes in some important way, new design methods
exploiting the change compete for market share of designer mind-time,
in an ad hoc process of diffusion. Bits and pieces of design
lore, design examples, design artifacts, and news of successful
market applications, move through the interactions of individual
designers, and through the trade and professional journals, conferences,
and mass media. When a new design methodology has become widely
integrated into practice in industry, we finally see textbooks
published and university courses introduced on the subject.
- I believe we can discover powerful
alternatives to that long, ad hoc, undirected process. Much of
this talk concerns the application of methods of experimental
computer science to the particular case bf the rapid directed
creation, validation, and cultural integration of the new VLSI
design and VLSI implementation methods within a large computer-communication
- First I will sketch the evolution
of the new VLSI design methods, the new VLSI design courses,
and the role that implementation played in validating the concepts
as they evolved. Next I'll bring you up to date on the present
status of the methods, the courses, and the implementation systems.
Finally, I'll sketch the methods that were used to direct this
evolutionary process. We'll reflect a bit on those methods, and
look ahead to other areas where such methods might be applied.
2. Evolution of the VLSI Design Courses; Role
of the MPC Adventures
- In the early 1970's, Carver
Mead began offering a pioneering series of courses in integrated
circuit design here at Caltech. The students in these courses
in MOS circuit design were presented the basics of industrial
design practice at the time. Some of these students went on to
do actual design projects, and Carver found that even those without
backgrounds in device physics were able to complete rather ambitious
projects after learning these basics. These experiences suggested
that it might be feasible
to create new and even simpler methods of integrated system design.
- In the mid 1970's, a collaboration
was formed between my group at Xerox PARC and a group led by
Carver here at Caltech, to search for improved methods for VLSI
design. We undertook an effort to create, document, and debug
a simple, complete, consistent method for digital system design
in nMOS. We hoped to develop and document a method that could
be quickly learned and applied by digital system designers, folks
skilled in the problem domain (digital system architecture and
design) but having limited backgrounds in the solution domain
(circuit design and device physics). We hoped to generate a method
that would enable the system designer to really exploit the architectural
possibilities of planar silicon technology without g;ving up
the order of magnitude or more in area-time-energy perforn-iance
sacrificed when using the intermediate representation of logic
gates as in, for example, traditional polycell or gate-array
- Our collaborative research on
design methodology yielded important basic results during '76
and '77. We formulated some very simple rules for composing FET
switches to do logic and make registers, so that system designers
could easily visualize the mapping of synchronous digital systems
into nMOS. We formulated a simple set of concepts for estimating
system performance. We created a number of design examples that
applied and illustrated the methods.
- Now, what could we do with this
knowledge? Write papers? Just design chips? I was very aware
of the difficulty of bringing forth a new system of knowledge
by just publishing bits and pieces of it in among traditional
- I suggested the idea of writing
a book, actually of evolving a book, in order to generate
and integrate the methods, and in August 1977 Carver and I began
work on the Mead-Conway text. We hoped to document a complete,
but simple, system of design knowledge in the text, along with
detailed design examples. We quickly wrote a preliminary draft
of the first three chapters of this text, making use of the Alto
personal computers, the network, and the electronic printing
systems at PARC. In parallel with this, Carver stimulated work
on an important design example here at Caltech, the work on the
"OM2". Dave Johannsen carefully applied the new design
methods as they were being documented, refined and simplified,
to the creation of this major design example.
- We then decided to experimentally
debug the first three chapters of material by interjecting them
into some university MOS design courses. An initial draft of
the first three chapters [1(a)] was used by Carlo Sequin at U.C.
Berkeley, and by Carver Mead at Caltech in the fall of '77. During
the fall and winter of '77-78, Dave Johannsen finished and documented
the new OM2 design. The OM2 provided very detailed design examples
that were incorporated into a draft of the first five chapters
[1(b)] of the text. We distributed that draft in February '78
into spring semester courses by Bob Sproull at CMU, and by Fred
Rosenberger at Washington University, St. Louis.
- We were able to debug and improve
the material in these early drafts by getting immediate feedback
from the '77-78 courses. We depended heavily on use of the ARPAnet
for electronic message communications. Our work rapidly gained
momentum. A number of people joined to collaborate with us during
the spring of '78: Bob Sproull at CMU and Dick Lyon at PARC created
the CIF 2.0 specification; Chuck Seitz prepared the draft of
Chapter 7 on self-timed systems; H. T. Kung and several others
contributed important material for Chapter 8 on Concurrent Processing.
By the summer of '78 we completed a draft of the manuscript of
the entire textbook [1(c)].
MIT78 VLSI Design Course
- During the summer of 1978, 1
prepared to visit M.I.T. to introduce the first VLSI system design
course there. This was to be a major test of the full set of
new methods and of a new intensive, project-oriented form of
course. I also hoped to thoroughly debug the text prior to publication.
I wondered: How could I really test the methods and test the
course contents? The answer was to spend only half of the course
on lectures on design methods, then in the second half, have
the students do design projects. I'd then try to rapidly implement
the projects and see if any of them worked (and if not, find
out what the bugs were). That way I could discover bugs, or missing
knowledge, or missing constraints in the design methods or in
the course contents.
- I prepared a detailed outline
for such a course, and printed up a bunch of the drafts of the
text. Bob Hon and Carlo Sequin organized the preparation of a
"Guide to LSI Implementation, 2nd Ed., that contained lots
of practical information related to doing projects, including
a simple library of cells for 1/0 pads, PLA's, etc. I then travelled
to M.I.T., and began the course. It was a very exciting experience,
and went very well. We spent seven weeks on design lectures,
and then an intensive seven weeks on the projects. Shortly into
the project phase it became clear that things were working out
very well, and that some amazing projects would result from the
- While the students were finishing
their design projects, I cast about for a way to get them implemented.
I wanted to actually get chips made so we could see if the projects
worked as intended. But more than that, I wanted to see if the
whole course and the whole method worked, and if so, to have
demonstrable evidence that it had. So I wanted to take the completed
layout descriptions and very quickly turn them into chips, i.e.
implement the designs (We use the term "VLSI implementation"
for the overall process of merging the designs into a starting
frame, converting the data into patterning format, making masks,
processing wafers, dicing the wafers into chips, and mounting
and wire-bonding the chips into packages).
- We were fortunate to be able
to make arrangements for fast implementation of those student
projects following the MIT course. I transmitted the design files
over the ARPAnet from M.I.T. on the east coast to some folks
in my group at PARC on the west coast. The layouts of all the
student projects were merged together into one giant multiproject
chip layout, a trick developed here at Caltech, so as to share
the overhead of maskmaking and wafer fab over all of the designs.
The project set was then hustled rapidly through the prearranged
mask and fab services. Maskmaking was done by Micro-Mask, Inc.,
using their new electron-beam maskmaking system, and wafer fabrication
was done by Pat Castro's Integrated Circuit Processing Lab (ICPL)
at HP Research, in Palo Alto. We were able to get the chips back
to the students about six weeks after the end of the course.
A number of the M.I.T. '78 projects worked, and we were able
to uncover what had gone wrong in the design of several of those
- The M.I.T. course led to a very
exciting group of projects, some of which have been described
in later publications. I'll now show a map and some photos of
the project chip (see Ref. 6). The project by Jim Cherry, a transformational
memory system for mirroring and rotating bit map image data,
is particularly interesting, and was one of those that worked
completely correctly. Jim's project is described in detail in
the second edition of the Hon and Sequin Guidebook (see Ref,
5). Another interesting project is the prototype LISP microprocessor
designed by Guy Steele, that was later described in an
M.I.T. AI Lab report .
- As a result of this course and
the project experiences, we uncovered a few more bugs in the
design methods, found constraints that were not specified, topics
that were not mentioned in the text, that sort of thing. You
can see that the project implementation did far more than test
student projects. It also tested the design methods, the text,
and the course.
- During the spring of '79 we
began preparing the final manuscript of the Mead - Conway text
for publication by Addison-Wesley the following fall. Hon and
Sequin began preparing a major revision of the Implementation
Guide  that would contain important things like a CIF primer,
new, improved library cells, and so forth. I began preparing
an "Instructor's Guide", based on the experiences and
information from the M.I.T. '78 VLSI design course , containing
a detailed coure outline, a complete set of lecture notes, and
homework assignments from that course. These materials
would help transport the course to other environments.
MPC Adventures. MPC79 and MPC580
- I'll now describe the events
surrounding the multiproject chip network adventures of the fall
of 1979 and spring of 1980. 1 remember thinking: "Well,
ok, we've developed a text, and also a course curriculum that
seems transportable. The question now is, can the course be transported
to many new environments? Can it be transported without one of
the principals running the course?" In reflecting on the
early work on the text by communicating with our collaborators
via the ARPAnet, and by thinking about which schools might be
interested in offering courses, I got an idea: If we could find
ways of starting project-oriented courses at several additional
schools, and if we could also provide VLSI implementation for
all the resulting student projects, we could conduct a really
large test of our methods. The course might be successful in
some schools, and not in others, and we could certainly learn
a lot from those experiences. I began to ponder the many ways
we could use the network to conduct such an adventure.
- We began to train instructors
from a number of universities in the methods of teaching VLSI
design. Doug Fairbairn and Dick Lyon ran an intensive short course
for PARC researchers during the spring of '79, and a videotape
 was made of that entire course. During the summer of '79,
we began using those tapes as the basis for short, intensive
"instructor's courses" at PARC for university faculty
members. Carver Mead and Ted Kehl also ran an instructor's course
at the University of Washington, with the help of the PARC tapes,
in the summer of '79. All "graduates" of the courses
received copies of the Instructor's Guide, to use as a script
at their schools.
- By early fall of '79, quite
a few instructors were ready to offer courses. We at PARC gathered
up our nerve, and then announced to this group of universities:
"If you run courses, we will figure out some way so that
at the end of your course, on a specified date, we will take
in any designs that you transmit to us over the ARPAnet; we will
implement those projects, and send back wirebonded, packaged
chips for all of your projects within a month of the end of your
course!" This multi- university, multiproject chip implementation
effort came to be known as "MPC79".
- About a dozen universities joined
to participate in MPC79. As this large university community became
involved, the project took on the characteristics of a great
"network adventure", with many people simultaneously
doing large projects to test out new ideas. Through the implementation
effort, students hoped to validate their design projects, instructors
would be able to validate their offering of the course, and we
would be able to further validate and test the design methodology
and the new implementation methods in development at PARC.
- We coordinated the MPC79 events
by broadcasting a series of detailed "informational messages"
out over the network to the project lab coordinators at each
school. MSG#1 announced the service and the schedule; MSG#2 distributed
the basic library cells, including I/0 pads and PLA cells; MSG#3
described the "User's Guide" for interactions with
the system; MSG#4 contained information about the use of CIF2.0;
MSG#5 provided last-minute information just prior to the design
deadline; MSG#6 was sent just after the implementation was completed,
and contained news about the results of the entire effort. Figure
1. flowcharts the overall activity.
- Figure 1. Flowchart of the
overall MPC79 activity:
- During this period, Alan Bell
pioneered the architecture and teamed up with Martin Newell to
develop a "VLSI Implementation System", which is something
like a time-sharing operating system, or information management
system, for providing remote access to mask and fab services.
This system manages all user interactions, manages the data base
of design files, handles the logistics, the scheduling, enabling
users all around the country to interact by electronic messages
with (what they perceive to be) an automatic system that implements
- Figure 2 shows a simple block
diagram of the basic modules of the system. It contains a user
message handier and an associated design file processing subsystem;
these provide a means for interacting with users to receive requests
for service, transmit status and error messages, and build the
design-file data base. It also contains a die-layout planning
and design-file merging subsystem used to pack all of the participants
designs together into a mask specification following the design
deadline time. Finally it contains a CIF to MEBES (electron beam
maskmaking) format-conversion subsystem to prepare the data files
for hand off to the foundry.
- Figure 2. Block Diagram
of the VLSI Implementation System:
- Following is a photo (Fig. 3)
of Alan Bell operating the implementation system at PARC during
the very final stages of project merging following the MPC79
design deadline. He's taken almost all of the designs, as identified
in a display menu listing the project ID's, and packed them into
the 12 die- types of the project set.
- Figure 3. Alan Bell using
the Implementation System to merge the MPC79 projects:
- For MPC79, the implementation.
system produced MEBES mask specifications containing 82 projects
from 124 participating designers, merged into 12 die-types that
were distributed over two mask sets. Thus there was a tremendous
sharing of the overhead involved in the maskmaking and wafer
fab. For MPC79 the masks were again made by Micro-Mask, Inc.,
and wafer fabrication was again done by HP-ICPL, Several chips
of each project type were custom wire-bonded and prepared for
shipment back to the designers, along with "implementation
documentation" containing pinout information for the
projects, electrical parameter measurements for the wafer lots,
etc. Figure 4 provides a visualization of the many projects conveyed
through one of the MPC79 wafer types, and of the corresponding
of hierarchy of information associated with the project set.
- Figure 4a. Photo of MPC79
type-A wafer type-AE die, type AE-7 chip:
Figure 4b. Corresponding hierarchy
of informational material:
- Just 29 days after the design deadline
time at the end of the courses, packaged custom wire-bonded chips
were shipped back to all the MPC79 designers. Many of these worked
as planned, and the overall activity was a great success. I'll
now project photos of several interesting MPC79 projects. First
is one of the multiproject chips produced by students and faculty
researchers at Stanford University (Fig. 5). Among these is the
first prototype of the "Geometry Engine", a high performance
computer graphics image-generation system, designed by Jim Clark.
That project has since evolved into a very interesting architectural
exploration and development project. 
- Figure 5. Photo of MPC79
- (containing projects
from Stanford University):
- Another project that turned up in
MPC79 was a LISP microprocessor  designed by Holloway, Sussman,
and Steele at MIT and Bell at PARC. This "Scheme-79"
chip is a further step in the evolution of LISP microprocessor
architectures by the M.I.T. AI-Lab group. Their work is based
on the prototype LISP microprocessor3 Guy Steele designed for
the 1978 MIT course.
- The results of this design methodology
experimentation and demonstration were very exciting, and convinced
us of the overall merits of the design methods, the courses,
and the implementation infrastructure. We first reported on the
results at the M.I.T. VLSI conference in Jan. 1980 [11,12].
- At PARC we then began the transfer
of the implementation system technology to an internal operational
group; the transfer was completed during the spring of 1980.
That operational group now has the responsibility of providing
VLSI implementation service within Xerox. They ran the implementation
system for a very large group of schools in the spring of 1980,
in order to provide themselves with a full-scale test the overall
operation of the system, and to confirm the success of the technology
transfer. That effort, known as "MPC580" , had
about twice as many participants as did MPC79. Over 250 designers
were involved! They produced so many projects, including a number
of full-die sized projects, that 5 mask sets were required. Although
MPC580 involved a lot of maskmaking and wafer fabrication, the
project set was turned around from design- cutoff to packaged
chips in about six weeks.
- Some really interesting projects
were created by the MPC580 designers. An example is the RSA encryption
chip  designed by Ron Rivest at MIT. Ron is a computer science
theoretician and faculty member at M.I.T., had taken the VLSI
design course the previous fall, and had done a small project
for MPC79. He and several other M.I.T. people then created the
prototype RSA encryption chip architecture and design during
the spring of 1980, in time for the MPC580 cutoff.
- I think you can now begin to see
the role the provision of implementation plays in stimulating
architectural exploration, the offering of design courses, and
the creation of design environments.
Status of the VLSI Design Courses
- and the VLSI Implementation Systems
- The design methodology introduced
in the Mead-Conway text has now become well integrated into the
university computer science culture and educational curriculum.
During the '79-'80 school year, courses were offered at about
12 universities. During the present '80-'81 school year, courses
are being offered at more than 80 universities.
- In addition, a number of industrial
firms have begun to offer internal, intensive courses on the
design methodology. For example, courses are being offered at
several locations within Hewlett-Packard, under the leadership
of Merrill Brooksby, Manager of Corporate Design Aids at HP.
The HP courses are project oriented, and provide students with
fast-turnaround project implementation. Brooksby believes that
in addition to directly improving the skills of HP designers,
the course plays an important role by providing a common internal
base of design knowledge through which designers can communicate
about work in other technologies (the "common culture effect").
Similar courses are being offered at DEC, in an effort led by
Lee Williams. Many other industrial firms have begun using an
excellent videotape VLSI system design course produced recently
by VLSI Technology, Inc. (VTI) .
- Design aid concepts and software
are evolving rapidly in the university VLSI research community.
During the work on MPC79, we began to see very interesting new
types of analysis aids originating at MIT. I'm thinking of the
work of Clark Baker, Chris Terman, and Randy Bryant who began
creating circuit extractors, static checkers, and switch simulators
of a sort appropriate for our design methods [16,17]. They began
to provide access to such analysis aids over the network, aids
that could be easily and efficiently used to partially validate
projects prior to implementation. These tools were used to debug
some large projects prior to submission to MPC79 (for example,
the Scheme-79 chip). Some of these tools are now in routine use
at a number of other universities. I believe we'll soon see analysis
aids embodying these new concepts placed into widespread use
- A VLSI implementation system has
been put into use by Xerox Corporate Research to support exploratory
VLSI system architecture and design within Xerox Corporation.
Another implementation system is being operated by USC-ISI for
the Defense Advance Research Projects Agency's (DARPA) VLSI research
community, a community consisting of several large research universities
(including M.I.T., CMU, Stanford, U.C. Berkeley, Caltech, etc.),
and a number of Defense Department research contractors. (Danny
Cohen will describe that system in a later talk)
- The initial system architecture
of the system used for MPC79, and the operational experiences
during MPC79, provided the knowledge on which the new Xerox and
ISI systems were based. One of the major improvements contained
in both these newer systems is the fully-automated handling of
user electronic message interactions and management of the design
file data base. During MPC79, Alan Bell interacted with the designers
with some machine assistance in message handling (using a menu-based
graphical interface that made message-processing and file management
interactions easy and fast), but in fact he did actually look
at all user messages. When we ran MPC79, we couldn't predict
the bounds on the information that would have to be conveyed
between designer and system. The generation of that knowledge
was an important result of MPC79, making it possible to automate
the message handling and data base management in later systems.
Our knowledge about the implementation system to foundry interface
was also considerably expanded and refined during these experiences
- As I think back over the origins
of the VLSI implementation system, it's clear that we didn't
initially set out to create such a system. It was really a serendipitous
result. We were extremely motivated and driven to provide VLSI
implementation to a large university community. I thought that
it just might be possible to do that. I realized that pulling
off VLSI implementation on such a vast scale would generate and
propagate a lot of artifacts, and thus announce the presence
of the new design culture, and help to culturally integrate our
methods. So, we began working very hard at PARC to create ideas
to bring down the cost per project and the overall turnaround
time, and to scale up capabilities for handling as many designers
- Somewhere along the line I began
to use the metaphor that "we're creating something for mask
and fab that was like the time-shared operating system was for
computing systems". Our idea was to create a system that
provided remote-entry, time and cost-sharing access to expensive
capital equipment, and that also managed the logistics of providing
such access to a large user community.
- At that time, and even now in most
integrated circuit design environments, the maskmaking and wafer
fabrication required to implement prototypes for a design project
cost about $15,000 to $20,000, and with some luck take only three
or four months getting through the various queues. (Designers
using internal company facilities may not see those costs, but
I guarantee they're there; on the other hand, all IC designers
are familiar with those long turnaround times). With that as
background, we were really amazed when we added up the costs
in dollars and time to implement the projects in MPC79. By using
the implementation system to provide shared access for a large
community of users to what amounts to a "fast-turnaround
silicon foundry" for rapid maskmaking and wafer fabrication,
we achieved a cost per project on the order of a few hundred
dollars, and a total turnaround time of only 29 days! (And remember,
we weren't using internal mask and fab facilities at PARC,
but were instead going to outside foundry services.)
- TABLE 1.
- [ Reprinted with permission
LAMBDA, The Magazine of VLSI Design  ]
- Computing and Design Environments
for 1980-81 VLSI Design
- at Universities that participated
- Thus we had demonstrated that the
time and cost to implement a prototype VLSI designs were as low
as they would be using TTL for an equivalent size designs. However,
once you've successfully prototyped a design in VLSI, you can
take tremendous advantage of the low replication costs and high-performance
of VLSI when competing against similar systems implemented in
TTL. Therefore, I believe that in addition to the many business
opportunities in VLSI design aids and chip designs, there must
also be a substantial business opportunities in the area of VLSI
implementation systems and services, foundry service brokerage,
and foundry services.
- Those of you who are interested
in learning more about the present courses and design aid environments
in the universities might read my recent column  in Lambda
Magazine. I'll now show a table (see Table 1.) from that
article that tabulates the courses, the computing and design-aid
environments (as of summer 1980), and the project experience
at the key group of 12 universities that collaborated with us
at PARC during MPC79 and MPC580. You can see some interesting
patterns of diffusion and convergence in this table. You can
see how new types of analysis aids arc being used this year at
most schools to qualify projects for implementation, and how
rapidly those new concepts have swept through this university
community, most of whom are on the ARPAnet.
4. Sketch of and Reflections on the Research Methods Used
- How was all of this done? Let's
reflect on these events, focussing on the research methods used
to direct and help all of these different things jointly evolve.
You'll notice a common idea running through all of these events:
Fast-turnaround implementation provides a means for testing concepts
and systems at many levels. It isn't just used for testing the
project chips. It also tests the design environments, the courses
and instructional methods, the text materials, and the design
- I'll now describe a basic method
of experimental computer science, and sketch how this method
was applied to the generation of the VLSI design and implementation
methodologies. Later I'll describe the resources required in
order to direct this sort of large scale, experimental evolution
of engineering knowledge and design practices.
- There is a basic experimental method
that is used in experimental computer science when we are exploring
the space of what it is possible to create. The method is especially
applicable when creating computer languages, operating systems,
and various kinds of computing environments, i.e., applications
where we provide primitives that many other people will use to
generate larger constructs. Suppose that you've conceived of
a new system concept, and want to try it out experimentally.
The method is simple: You build a prototype of a system embodying
that concept, run the system, and observe it in operation. You
might immediately decide, "Hey, this is just not feasible,"
and scrap the idea right there; or you may think, "Well,
maybe we can improve things," or, "Let's try something
slightly different," make some revisions, and run the system
again. This simple, iterative procedure is sketched in Figure
6. After the experimentation has generated sufficient knowledge
(for example, has demonstrated the feasibility of the concept),you
may make a transition into some later phase in the evolution
of the concept.
- What might such later phases be?
Suppose you've successfully taken a new concept through a feasibility
test, perhaps experimenting with a quick implementation that
you ran yourself. You may think, "Well, let's build an improved
prototype, and have some other user run it. I'll watch the user
use it, and see what happens." After going around that loop
a few times, and making further
refinements, you may make the
transition to building a prototype to be placed in trials by
many users. Thinking back, you can see how the design course
was taken through a succession of such phases, from feasibility
to transfer to a few other "users" and on to full scale
"field trials". By obtaining feedback from users and
observing results at each step, you move on to on the next phase
(see Fig. 7) of refinement and integration of that particular
- Figure 6. An Experimental
- Figure 7. Some Phases
in the Evolution of a System:
- If we study the development of the
VLSI design methodology, its validation, and its social propagation,
you'll notice that the following has happened: The evolution
of the methodology involved a multilevel cluster of systems that
were being jointly evolved (see Fig. 8). Each system in the cluster
runs through the experimental loops, and passes through the various
phases of its own evolution. Entries at the higher levels, for
example the methodology, or the text, or the documents to support
a course, might be more solid and in later phases of their evolution
at any given time than, for example, a course in a particular
school, or the design environment for that course.
- Student design projects play a key
role in this process, supporting new refinements in the higher
level systems in the hierarchy every new school semester. Fast
turnaround implementation of designs was used to close the experimental
loop on all the systems in this hierarchy.
- Figure 8. The Joint Evolution
of the Multi-Level Cluster of Systems:
- If we think back over the evolution
of these systems, we can see how all these things were running
in parallel in a rapidly enlarging social enterprise. The early
courses run here at Caltech demonstrated that it might be feasible
to create a simple design methodology. Following the period of
basic design methodology research, the preliminary courses run
at Caltech, U.C. Berkeley, and CMU helped debug the emerging
text documenting the new design methods. The newly documented
methodology was then introduced into the M.I.T. '78 course, which
became the prototype for the new type of intensive, project-oriented
courses. The results of that course prepared the way for seeding
similar courses in many other schools.
- The text itself passed through drafts,
became a manuscript, went on to become a published text. Design
environments evolved from primitive CIF editors and CIF plotting
software on to include all sorts of advanced symbolic layout
generators and analysis aids. Some new architectural paradigms
have begun to similarly evolve. An example is the series of designs
produced by the OM project here at Caltech. At MIT there has
been the work on evolving the LISP microprocessors [3,10]. At
Stanford, Jim Clark's prototype geometry engine, done as a project
for MPC79, has gone on to become the basis of a very powerful
graphics processing system architecture , involving a later
iteration of his prototype plus new work by Marc Hannah on an
image memory processor .
- While these things were evolving,
Dick Lyon undertook the important work of developing, debugging,
and evolving a set of basic library cells (see refs. 2,5) that
would later be used in all of the courses by all of the
students in the MPC adventures. Again. in parallel with that,
there was the iterative evolution through a series of experiments,
from the early multiproject chip sets to the remote entry multiproject
chip done at MIT, to the early implementation systems at PARC,
and now on to the automated implementation systems at PARC and
- One thing to remember about this
is that such enterprises are organized at the meta-level of research
methodology and social organization; they are not planned in
fully-instantiated detail using some sort of PERT chart. The
evolution of a system of knowledge has a certain dynamics.
There is a great deal that happens concurrently. There is the
necessity for various activities to reach some minimum sufficient
stage of development in order to support activity at some other
level. If things are staged right, and people are in close contact
with each other and are highly motivated by effective leadership,
then a lot of these things can move rapidly forward together.
But remember, there is always a strong element of chance when
folks go off exploring. The unfolding of the events depends upon
what is discovered, and upon how well the opportunities presented
by the discoveries are seized upon and exploited by the overall
community of explorers.
- Some key resources are required
in order to organize such an enterprise. Perhaps the most important
capital resource that we drew upon was the computer-communications
network, including the communications facilities made available
by the ARPAnet, and the computing facilities connected to the
ARPAnet at PARC and at various universities. Such a computer-communication
network is a really key resource for conducting rapid, large
scale, interactive experimental studies.
- The networks enable rapid diffusion
of knowledge through a large community because of their high
branching ratios, short time-constants, and flexibility of social
structuring; any participant can broadcast a message to a large
number of other people very quickly. It isn't like the phone,
where the more people you try to contact, the more time-overhead
is added so that you start spending all of your time trying to
get your messages around instead of going on and doing something
- The high social branching ratios
and short communications time constants of the networks also
make possible the interactive modifications of the systems, all
of these systems, while they are running under test. If someone
running a course, or doing a design, or creating a design environment
has a problem, if they find a bug in the text or the design method,
they can broadcast a message to the folks who are leading that
particular aspect of the adventure and say, "Hey! I've found
a problem." The leaders can then go off and think, "Well,
my God! How are we going to handle this?" When they've come
up with some solution, they can broadcast it through the network
to the relevant people. Thus they can modify the operation of
a large, experimental, multi-person, social-technical system
while it is under test. They don't have to run everything through
to completion, and then. start all over again, in order to handle
contingencies. This is a subtle but tremendously important function
performed by the network, and is similar to having an interactive
run-time environment when creating and debugging complex software
- There is another thing that happens
in the network: it's relatively easy to get people to agree to
standards of various kinds, if the standards enable access to
interesting servers and services. For example, CIF became a de
facto standard for design layout interchange because we at
PARC said "if you send a CIF file to us we will implement
your project". Everybody put their designs in CIF!
- We answered our own questions: "Is
CIF documented well enough to be propagated around? Does it really
work anyway? Does it have the machine independence we've tried
for?" That way we debugged CIF and culturally integrated
- Such networks enable large, geographically
dispersed groups of people to function as a tightly-knit research
and development community. New forms of competitive-collaborative
practices are enabled by the networks. The network provides the
opportunity for rapid accumulation of sharable knowledge. Much
of what goes on is captured electronically - - designs, library
cells, records of what has happened in the message traffic, design-aid
software and knowledge - - all can be captured in machine
representable form, and can be easily propagated and shared.
- One reason for the rapid design-environment
development during '79-'80 was a high degree of collaboration
among the schools. Often, as useful new design aids were created,
they were quickly shared. Many of the schools had similar computing
environments, and the useful new knowledge diffused rapidly via
- Another reason for rapid progress
was keen competition among the schools and among individual participants.
The schools shared a common VLSI design culture; during '79-'80
all used the same implementation system, and batches of projects
from the schools were often implemented simultaneously. Therefore,
project creation, innovations in system architecture, and innovations
in design aids at each of the schools were quite visible to the
others. Students and researchers at MIT, Stanford, Caltech, CMU,
U.C. Berkeley, etc., could visualize the state of the art of
each other's stuff. These factors stimulated competition,
which led to many ambitious, innovative projects.
- Successful completion of designs,
and thus participation in such competition, depended strongly
on the quality of the design environment in each school. Therefore,
there was strong pressure in each school to have the latest,
most complete set of design aids. This pressure tended to counter
any "not invented here" opposition to importing new
ideas or standards. The forces for collaboration and for competition
were thus coupled in a positive way, and there was "gain
in the system".
- Now, think back to the question,
"How do unsound methods become sound methods?"
Remember, you need large scale use of methods to validate
them, and to produce the paradigm shifts so that the methods
will be culturally integrated. In industry, it's very difficult
to take some new proposed technique for doing things and put
it in use in a large scale in any one place; a manager trying
such things would be accused of using unsound methods. However,
in the universities, especially in graduate courses in the major
research universities, you have a chance to experiment in a way
you might not in industry, a way to get a lot of folks to try
out your new methods.
- A final note about our methods:
The major human resources applied in all of these adventures
were faculty members, researchers, and students in the universities.
The research of the VLSI System Design Area has often involved
the experimental introduction and debugging of new technical
and procedural techniques by using the networks to interact with
these folks in the universities. These resources and methods
were applied on a very large scale in the MPC adventures. There
are risks associated with presenting undebugged technology and
methods to a large group of students. However, we have found
the universities eager to run these risks with us. It is exciting,
and I believe that it is appropriate for university students
to be at the forefront, sharing in the adventure of creating
and applying new knowledge. The student designers in the MPC
adventures not only had their projects implemented, but also
had the satisfaction of being part of a larger experimental effort
that would impact industry-wide procedures.
- These experiences suggest opportunities
and provide a script for university-government-industry collaboration
in developing new design methodologies and new supporting infrastructure
in many areas of engineering design. The universities can provide
the experimental and intellectual arena; government can provide
infrastructure and university research funding; industry can
provide knowledge about and access to modem, expensive, capital
equipment that can implement experimental designs created by
university students and researchers. Modern computer- communications
networks, properly used, can tie all these activities together.
The implementation of designs closes all the experimental loops.
- I wonder where we might apply some
of these methods next? Where might some of you apply methods
like these in order to aggressively explore new areas? Well,
first of all, there certainly are tremendous opportunities for
further discoveries and evolutionary progress in VLSI design
and implementation methodology.
- We are now seeing the beginnings
of new architectural methodologies appropriate for VLSI in a
number of specialized areas of application. For example you might
study the work that Dick Lyon is doing to create a new architectural
set of "VLSI building blocks" for bit-serial digital
signal processing . Wouldn't it be interesting if those techniques
could now be tried in a few courses? We'd find out if people
can really learn about signal processing with VLSI, and then
quickly compose working systems, thus providing a reality test
of Dick's ideas.
- There are many other areas of digital
system architecture ripe for the introduction of new architectural
methodologies appropriate for VLSI. There are areas like computer
graphics for providing high-bandwidth visual displays for interactive
personal computing systems, and the generation of computer images
for electronic printing and plotting. There's image processing,
taking digitized input image data and processing it to recognize
and detect things, with applications in OCR systems, visual input
systems for controlling robots, smart visual sensors for various
defense systems, that sort of thing. There are areas like data
encryption and decryption. So there's a whole world of specialized
architectural areas that people can now explore, given that they
have access to a VLSI design environment and to quick turnaround
implementation to try out their ideas. As successes accumulate,
the underlying knowledge and the detailed design files can be
rapidly propagated around the VLSI network community.
- There are many opportunities for
evolving new design and analysis aids appropriate for the new
design methodology. Progress has been rapid so far ,
but there is plenty more to do. Those interested in creating
and testing new design aids might ask yourselves "What can
I create and then introduce over the network that would be valuable
to the VLSI community, that might integrate with the overall
activity?" That line of thinking, taking into account the
current state of the community, and the means of introducing
new ideas into the community for testing and validation, may
increase your chances of successfully creating something that
becomes culturally integrated.
- For example, the early circuit extractor
work done by Clark Baker  at MIT became very widely known
because Clark made access to the program available to a number
of people in the network community. From Clark's viewpoint, this
further tested the program and validated the concepts involved.
But Clark's use of the network made many, many people aware of
what the concept was about. The extractor proved so useful that
knowledge about it propagated very rapidly through the community.
(Another factor may have been the clever and often bizarre error-messages
that Clark's program generated when it found an error in a user's
- Another area of' opportunity is
in the evolution of standards. For example, we need a standard
process test chip" for the back-end foundry interface, so
that designers and foundry operators will have a mechanism for
deciding to shake hands and exchange dollars for wafers. Although
some strawman versions have been proposed, there is no standard
now. Perhaps a standard process test chip could be evolved by
inserting strawman versions into wafers that are run for university
multiproject chips sets. The community could then gradually converge
on a workable standard.
- There are opportunities for further
evolution of implementation systems, Also, similar design and
implementation methods could be mapped into technologies other
than nMOS. Design primitives, design rules, and design examples
could be created, for example, for CMOS and then run through
the same kind of scenario as above to introduce those into a
- I myself have become interested
in the prospects for bringing about a convergence of the work
in VLSI design methodology with work based in knowledge engineering
[22,23]. There is the possibility of creating knowledge-based
expert systems to aid VLSI system designers. I can imagine directing
die evolution of such expert systems by using similar methods
to those described above: trying out ideas, prototyping them,
evaluating them, and bringing them in large-scale use within
a computer- communication network community. But an added twist
is possible here, that of making knowledge about expert systems
accessible to the larger CS community, a community now knowing
about VLSI. That way we could help to generate a common literacy
about knowledge, a common knowledge representation language,
and knowledge about the methods of knowledge engineering.
- You'll note that the experimental
methods described in this talk aren't limited to application
in the exploration of microelectronic system design. I find it
fascinating to think about applying these methods to the rapid
exploration of other domains of engineering design that may be
operating under new constraints, and thus be full of new opportunities.
- For example, it is becoming common
in some industrial environments for folks to do mechanical
system design by using computers to specify the shape and
dimensions of parts and to generate the tapes for numerically
controlled machine tools that can implement the parts. Consider
the opportunity here: What if we documented a simple design method
for creating mechanical systems under the assumption that the
parts are to be remotely machined and assembled in some sort
of magical automatic factory". Then ask the question, "Well,
how would you teach mechanical design tinder the many new constraints
imposed by the remote factory?" If you had access to such
a factory, or if you could even emulate it using manual procedures
where necessary, you could put in place the same sort of overall
experimental environment to develop from very early crude principles
some sort of new design methodology that would be appropriate
for that environment. In that way one could evolve an entire
design culture of methods, courses, design examples, design aids,
etc., using the methods described above, and that culture could
be rapidly spread out through the networks into a large university
- I am very interested in studying
and experimenting further with techniques for creating, refining,
and culturally integrating new engineering design methodologies.
If any of you folks engage in similar work, especially within
the university computer-communications network community, I'd
be very interested in learning of your experiences. I'd enjoy
brainstorming with you on how to improve the underlying methods,
and how to spread knowledge about the results.
Acknowledgements and Conclusions
- I am deeply indebted to many people
for their contributions and help in creating the design methods,
the textbook, and the implementation methods and system, and
also the university VLSI design courses, design environments,
and research programs. There are literally hundreds of people
who have played important roles in the overall activity. Students,
researchers, and faculty members in the universities, and a number
of industrial researchers, industrial research managers, and
government research program managers have been actively involved
in these events. I am at a loss to acknowledge all of the individual
- However, I would like to individually
acknowledge some of the folks at PARC who've worked on this research
since the early days. I am thinking of Doug Fairbairn, who was
with us during the key early years; Dick Lyon, who has contributed
so much to the effort; Alan Bell and Martin Newell for their
innovations and efforts in the creation of VLSI implementation
systems that have supported so well the validation and spread
of VLSI knowledge. I'd especially like to acknowledge the support
and encouragement that all of us at PARC have received over the
years from the senior research management of Xerox Corporation,
in particular, from Bert Sutherland.
- Let's look at the photo of Alan
Bell again (Fig. 3), and think back to the MPC79 effort. I'm
sure you now sense that MPC79 was not just a technical effort,
that there was a tremendous human dimension to the project. So
many folks were simultaneously creating and trying out things:
students and researchers trying out new designs that were very,
very important to them; instructors and project lab coordinators
trying out the new courses and project lab facilities; at PARC
the new implementation system was coming into existence, under
the pressure of trying to provide VLSI implementation service
to the many university designers. This built up into a tremendously
exciting experience for all participants, a giant network adventure
that climaxed as the design-cutoff time approached, and the final
rush of design files flowed through the ARPAnet to PARC.
- So when you see someone interacting
with a personal computer connected to a network, rather than
jumping to the conclusion that you are observing a reclusive
hacker running an obscure program, you might ask yourself "I
wonder what adventures this person is involved in?" Remember,
you may be observing a creatively behaving individual who is
participating in, or perhaps even leading, some great adventure
out in the network!
- These events are reminiscent of
the pervasive effects of the telegraph and the railroads, as
they spread out everywhere during the nineteenth century, providing
an infrastructure people could use to go on adventures, to go
exploring, and to send back news of what they had found. I think
of personal computers and the computer communication networks
as a similar sort of infrastructure, but here and now, as we
explore the modern frontier - - the frontier of what we can create.
- The new knowledge and products our
VLSI design community is creating will have tremendous social
impact, by helping rapidly spread and increasing the power of
the new personal computing and computer-communication
- Thus your work in computer science
and VLSI system design is expanding the opportunities for all
of us to go on all sorts of grand adventures in the future!
- 7. REFERENCES
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und Entwicklung einer wissenschafilichen Tatsache: Einjuhrung
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Laboratory Life.- The Social Construction of Scientific Facts,
Vol. 80, Sage Library of Social Research, Sage Publications,
Beverly Hills, 1979.
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Colleges. Diffusion of Knowledge in Scientific Communities, Univ.
of Chicago Press, Chicago, 1972.
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J. Norton, Advanced Intellecl-Augmentation Techniques, Stanford
Research Institute, Menlo Park, CA, 1972.
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"Applications of Information Networks", Proceedings
of the IEEE, Vol., 66, No. 11, November, 1978.
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Proceedings of the IEEE, Vol., 66, No. 11, November, 1978.
Lynn Conway's VLSI Archive > MPC Adventures