Using the Tools: the Story of Mead-Conway VLSI Design
While some of PARC's pioneers were getting restless by the mid-1970s, others were just beginning to find uses for the marvelous tools of the office of the future. One was Lynn Conway, who used the Alto, networks, and laser printers to develop a new method of designing integrated circuits and disseminate the method to hundreds of engineers at several dozen institutions around the country.
When Bert Sutherland came in as manager of the Systems Science Laboratory in 1975, he brought Carver Mead, a professor at the California Institute of Technology in Pasadena, to PARC to wander in and create some havoc." Mead was an expert in semi conductor design who had invented the MESFET in the late 1960s.
Sutherland had worked on the application of computer graphics to integrated-circuit layout, Conway recalled, so it was natural for him to think about applying an advanced personal computer like the Alto to the problem of IC design. Conway herself was drawn to integrated-circuit design by the frustration of the OCR-Fax project, in which she had conceived an elegant architecture that could only be realized as racks and racks of equipment. But those racks might become a few chips if only they could be designed by someone who knew what they should do and how they should fit together.
Carver Mead came up and gave a one-week course at PARC on integrated-circuit design," Fairbairn recalled. Lynn Conway and I were the ones that really got excited about it and really wanted to do something."
Then a whole bunch of things really clicked," said Conway. While Carver and I were cross-educating each other on what was going on in computing and in devices, he was able to explain some of the basic MOS design methods that had been evolving within Intel. And we began to see ways to generalize the structures that [those designers] had generated.'' Instead of working only on computer tools for design, Conway explained, she and Mead worked to make the design methods simpler and to build tools for the refined methods.
Between mid-'75 and mid-'77, things went from a fragmentary little thing-one of a number of projects Bert wanted to get going-to the point where we had it all in hand, with examples, and it was time to write."
In a little less than two years, [Carver] Mead and [Lynn] Conway had developed the concepts of scalable design rules, repetitive structures, and the rest of what is now known as structured VLSI design
In a little less than two years, Mead and Conway had developed the concepts of scalable design rules, repetitive structures, and the rest of what is now known as structured VLSI design-to the point where they could teach it in a single semester.
Today structured VLSI design is taught at more than 100 universities, and thousands of different chips have been built with it. But in the summer of 1977, the Mead-Conway technique was untested-n fact belittled. How could they get it accepted?
The amazing thing about the PARC environment in 1976-77 was the feeling of power; all of a sudden you could create things and make lots of them. Not just one sheet, but whole books," said Conway.
And that is exactly what she and her cohorts did. We just self-published the thing [Introduction to VLSI Systems]," said Conway, and put it in a form that if you didn't look twice, you might think this was a completely sound, proven thing."
It looked like a book, and Addison-Wesley agreed to publish it as a book. Conway insisted it couldn't have happened without the Altos. Knowledge would have gotten out in bits and pieces, always muddied and clouded-we couldn't have generated such a pure form and generated it so quickly.''
The one tool Conway used most in the final stages of the VLSI project was networks: not only the Ethernet within PARC, but the ARPAnet that connected PARC to dozens of research sites across the country. The one thing I am clear of in retrospect," said Conway, is the sense of having powerful invisible weapons that people couldn't understand we had. The environment at PARC gave us the power to outfox and outmaneuver people who would think we were crazy or try to stop us; otherwise we would never have had the nerve to go out with it the way we did."