Hoff thought designing 12 custom chips for a calculator was crazy, so he created the Intel 4004, the first commercially produced microprocessor.

High School

By the age of 12 Marcian Hoff started his explorations on electronics, building things with parts ordered from an Allied Radio Catalog, a shortwave radio kit, and surplus relays and motors salvaged from the garbage at his father’s employer, General Railway Signal Co. Then in high school, working mostly with second­hand components, he built an oscilloscope, an achievement he parlayed into a technician’s job at General Railway Signal.

Undergraduate

Hoff returned to that job during breaks from his undergraduate studies at Rensselaer Polytechnic Institute. There, he would repair the state-of-the-art Tektronix 545s, then move on to more interesting stuff, like inventing an audio frequency railroad­train tracking circuit and a lightning protection unit that gave him two patents before he was out of his teens.

The best thing about the job, Hoff recalled, was the access it gave him to components that were beyond the budgets of most engineering students in the 1950s—transistors, and even the just-introduced power transistor. He did an undergraduate thesis on transistors used as switches, and the cash prize he won for it quickly went for a Heathkit scope of his own.

Graduate

He chose California’s Stanford University for graduate school. While working toward his Ph.D. there, he did research in adaptive systems (which today are called neural networks) and, with his thesis advisor Bernard Widrow, racked up two more patents. After getting his degree, Hoff stayed at Stanford for six more years as a postdoctoral researcher, continuing the work on neural networks.

Industry

By 1968 student hostility to the government over the Vietnam War was growing and life for researchers on campus who, like Hoff, relied on government funding was looking as if it might get uncomfortable. Hoff had already been contemplating the possibilities of industrial jobs when he received a telephone call from Robert Noyce, who told him he was starting a new company, Intel Corp., and had heard Hoff might be interested in a job.

That year Noyce hired Hoff as a member of the technical staff, Intel’s 12th employee. Working on memory technology, Hoff soon received a patent for a cell for use in MOS random-access integrated circuit memory. Moving on to become manager of applications research, he had the first customer contact of his career.

Calculator

One group of customers with whom Hoff made contact were from Busicom Corp., Tokyo. Busicom had hired Intel to develop a set of custom chips for a low-cost calculator and had sent three engineers to Santa Clara to work on the chip designs.

Hoff quickly concluded that the engineers were going in the wrong direction. He thought designing 12 custom chips for a calculator was crazy. Twelve chips, each with more than 3000 transistors and 36 leads, were to handle different elements of the calculator logic and controls, and he surmised the packaging alone would cost more than the targeted retail price of the calculator. Instead of 12 chips, he felt, all of these could fit on a single chip.

The Busicom engineers had no interest in dumping their design in favor of Hoff’s unproved proposal. But Hoff, with Noyce’s blessing, started working on the project. Soon Mazor, then a research engineer at Intel, joined him, and the two pursued Hoff’s ideas, developing a simple instruction set that could be implemented with about 2000 transistors. They showed that the one set of instructions could handle decimal addition, scan a keyboard, maintain a display, and perform other functions that were allocated to separate chips in the Busicom design.

In October 1969, Hoff, Mazor, and the three Japanese engineers met with Busicom management, visiting from Japan, and described their divergent approaches. Busicom’s managers chose Hoff’s approach, partly, Hoff said, because they understood that the chip could have varied applications beyond that of a calculator. The project was given the internal moniker “4004.”

Federico Faggin was assigned to design the chip, and in nine months came up with working prototypes of a 4-bit, 2300-transistor “microprogrammable computer on a chip.” Busicom received its first shipment of the devices in February 1971.

Microprocessor Revolution

The microprocessor revolution was gearing up, albeit slowly. Hoff joined Faggin as a microprocessor evangelist, trying to convince people that general-purpose one chip computers made sense. Word went out. In May 1971 an article in Datamation magazine mentioned the product, and the following November Intel produced its first ad for the 4004 CPU and placed it in Electronic News. By 1972 stories about the miracle of what began being called the microprocessor started appearing regularly in the press, and Intel’s competitors followed its lead by launching microprocessor products of their own.

One step Hoff did not take at that time was apply for a patent. To him the invention seemed to be obvious, and obviousness was considered grounds for rejecting a patent application. Instead of patenting, Hoff in March 1970 published an article in the proceedings of the 1970 IEEE International Convention that stated: “An entirely new approach to design of very small computers is made possible by the vast circuit complexity possible with MOS technology. With from 1000 to 6000 MOS devices per chip, an entire central processor may be fabricated on a single chip.”

Consulting

He now spends half his time as a consultant and half pursuing technical projects of his own devising.

When a lawyer shows him a patent disclosure, even one decades old, he can determine whether or not it could then have been “reduced to practice” and whether it provided sufficient information to allow “one of ordinary skill in the art” to practice the invention. Then he can build a model proving his conclusion, using vintage components from his collection, and demonstrate the model in court as an expert witness.

Hoff sees this ability to get down to basics as one of his strengths. “I relate things to fundamental principles,” he said. “People who don’t question the assumptions made going into a problem often end up solving the wrong problem.”

Doing legal detective work appeals to Hoff for another reason: it gives him an excuse to hunt for interesting “antique” components at flea markets and electronics stores.

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References

1. Tekla S. Perry (October 8, 2022) "How Ted Hoff Invented The First Microprocessor" IEEE Spectrum