Computer scientists are more than just nerds with pocket packs," says John Hennessy. "They can have an appreciation for the arts and humanities and history as well as the sciences."
This pioneer in reduced-instruction-set computing (RISC) now has a chance to prove his point. Installed as president of Stanford University in 2000, Hennessy is responsible for a student population of some 14 000 and a program that boasts graduate schools of business, law, medicine, and engineering and offers undergraduate degrees in over 60 fields, including archaeology, drama, feminist studies, and music. He is the first computer scientist to head such a large and diverse U.S. university.
Hennessy has always been a pioneer. He helped evangelize RISC in the early 1980s when most people didn't believe computers with such an architecture would ever be much use, and he started a company that proved them wrong. He led the development of a new way of organizing cache memory in multiprocessors that in the late 1980s experts said was unworkable, but is today in wide use.
"My career parallels the coming of age of computer science," Hennessy, an IEEE Fellow, told IEEE Spectrum.
Hennessy's involvement in computing began some 35 years ago in New York City when he was 16. The dominant small computer at that time was Digital Equipment Corp.'s PDP-8 minicomputer, with a memory of up to 4096 12-bit words and a processing speed of a few hundred thousand instructions per second. The microprocessor had yet to be invented.
Relays, meanwhile, were cheap and abundant, costing less than a dollar each. "And," Hennessy says, "you could do some interesting computing if you had enough relays." So he and a friend decided to build a computer that would play tic-tac-toe. They used about 20 multipole relays.
"We didn't know the basics of logic design or switching theory," Hennessy recalls. "But we were able to figure out the decision tree for tic-tac-toe. And then we made a really important decision—we put red and green lights on the front and covered the whole thing in black Contac paper, which was absolutely crucial to get the right effect." People were astounded that this device could win.
Flush with the success of his tic-tac- toe computer, which won an award at a local science fair, Hennessy decided to major in electrical engineering in college. He blasted through Villanova University (Villanova, Pa.) in three and a half years, then went on to the State University of New York at Stony Brook. Within six months, in 1974, he had started the research that would be his Ph.D. thesis.
A manager at Brookhaven National Laboratory (Upton, N.Y.) initiated that Ph.D. project when he asked Stony Brook's computer science department for help in solving a control problem. Brookhaven feared that its workers might, because of long-term radiation exposure, be losing bone density. Monitoring this loss required regular X-ray scans; but a device was needed to control the scanner and keep the X-ray intensity as low as possible by scanning as quickly as possible, yet still capture an adequate image.
Hennessy's faculty advisor suggested he try using a microprocessor to solve the problem. In those early days of microprocessor technology, the state of the art was the Intel 8008, which preceded Intel's 8086 and was programmed largely in assembly language. For his thesis, Hennessy decided to build a programming language that, along with the necessary compiler, would do real-time control. He worked on this project for three years. While the resulting system was only an academic prototype and was never used commercially, Hennessy says that some of the ideas that emerged in both specifying and checking real-time constraints were later incorporated in real systems.
When Hennessy started his research, the wider computer world had only limited interest in real-time systems. But just as he was finishing his Ph.D. in 1977, the technology suddenly began getting a lot of attention as its potential became apparent. "So this little field I was working in just exploded," he told Spectrum.