Federico Faggin and the Microprocessor

Silicon Gate Technology and Fairchild

Federico Faggin was born on December 1, 1941, in Vicenza, a small city in northern Italy known more for Palladian architecture than electronics. He showed an early aptitude for physics and mathematics, and enrolled at the University of Padova — one of the oldest universities in the world — where he completed a degree in physics in 1965.

He joined Fairchild Semiconductor’s Italian facility in Agrate Brianza, where he was assigned to work on metal-oxide-semiconductor (MOS) transistor technology. The MOS transistor was emerging as the key device for dense integrated circuits, but it had manufacturing problems. The standard approach used aluminum as the gate material — the electrode that controlled the transistor’s switching behavior — and this metal gate had to be deposited in a separate step from the transistor’s source and drain regions, making it difficult to align precisely. Misalignment increased the transistor’s size and introduced unwanted parasitic capacitance.

Faggin developed a solution: replace the aluminum gate with polycrystalline silicon. A silicon gate could be fabricated first, then used as a self-aligned mask for the source and drain implants — the same lithography step that defined the gate also defined where the current-carrying regions would be. This eliminated the alignment problem, making transistors smaller, faster, and more consistent. The technique became known as silicon gate technology (SGT).

In 1968, Faggin was transferred to Fairchild’s main laboratory in Mountain View, where he developed SGT into a manufacturable production process and designed the first commercial silicon gate integrated circuit: the Fairchild 3708. The process he developed became directly foundational to Intel’s MOS manufacturing capability — Intel hired him away from Fairchild specifically because of it.

The 4004: Architecture Is Not a Microprocessor

When Faggin joined Intel in April 1970, he walked into a situation that tested his abilities immediately. A year earlier, Intel had taken a contract from Busicom, a Japanese calculator company, to produce twelve custom chips for a high-end scientific calculator. Intel engineer Marcian “Ted” Hoff had proposed a bolder solution: instead of twelve specialized chips, design four more general chips, one of which — the CPU chip — would be programmable. A programmable processor could be instructed to perform any function, making it far more flexible than a chip hardwired to do one thing.

Hoff’s architectural proposal was genuinely innovative. But after a year of effort, the design team had not produced a manufacturable chip. The architecture specified what the processor should do; it said almost nothing about how to fit a complete CPU into the physical silicon area available, using a manufacturing process that had never been applied to a device of this complexity.

Faggin took the project over and immediately understood the gap. Architecture is a specification. A microprocessor is a physical artifact — transistors placed precisely on silicon, connected by metal pathways that have to fit within the heat budget, power budget, and area budget of the die. Getting from specification to silicon requires a kind of intimate knowledge of the manufacturing process — what you can and cannot ask the technology to do — that Faggin possessed and the rest of the team did not.

Over the following twelve months — nearly all of 1970 and into early 1971 — Faggin worked at a pace his colleagues described as extraordinary even by Intel’s standards. He designed the circuit for all four chips in the MCS-4 chipset: the 4001 ROM, 4002 RAM, 4003 shift register, and 4004 CPU. He created the physical layout of each chip. He applied silicon gate technology to achieve the transistor density the design required. He built prototype circuits, ran silicon through the fabrication process, tested the results, identified failures, corrected the design, and ran more silicon. He did much of this work at night and on weekends.

The 4004 — the CPU chip — contained 2,300 transistors on a die measuring 3 millimeters by 4 millimeters. It had a 4-bit data path and a 12-bit address bus. At its rated clock speed of 740 kHz, it could execute roughly 92,000 simple instructions per second. By the standards of 1971 minicomputers, its computing power was modest. But it was a complete CPU, including arithmetic logic unit, registers, and control logic, on a single piece of silicon.

Intel announced the 4004 publicly on November 15, 1971. The announcement appeared in Electronic News. The headline read: “Intel delivers computer on a chip.”

The Credit Dispute

The announcement copy described Hoff as the key inventor of the 4004 concept. Faggin — who had designed every circuit in the chip and developed the manufacturing technology that made it possible — was mentioned only incidentally. This characterization persisted in Intel’s official history for decades.

Faggin objected, consistently and publicly. His argument was not that Hoff’s architectural contribution was insignificant — it was not — but that architecture without implementation is not an engineering product. Hoff had conceived what the microprocessor should do; Faggin had made it real, through twelve months of design work that required both deep knowledge of silicon gate technology and the ability to apply it to a circuit of unprecedented complexity. Without Faggin, the 4004 would have remained an idea.

The 8008, Intel’s Growing Indifference, and the Exit

Faggin continued at Intel after the 4004, designing the Intel 8008 (1972) — the first 8-bit microprocessor. The 8008 originated from a separate project: CTC, a Texas company, had contracted Intel to develop a terminal processor. The contract was eventually cancelled by CTC, but Intel retained the rights to market the chip. The 8008 became the first microprocessor widely used in hobbyist computers, and its instruction set architecture directly influenced the 8080 and 8085 that followed.

Faggin’s frustration with Intel grew through 1973 and 1974. He felt that Intel’s management — focused primarily on the memory business, which was generating most of the company’s revenue — undervalued the microprocessor division and its engineers. He also remained aggrieved by the credit situation around the 4004. In late 1974, he left Intel.

Zilog and the Z80

In 1974, Faggin co-founded Zilog with Ralph Ungermann, with venture capital funding from Exxon Enterprise. Zilog’s first product was the Z80 microprocessor, announced in 1976.

The Z80 was designed to be fully software-compatible with Intel’s 8080 — programs written for the 8080 would run on the Z80 without modification — while adding substantially more capability. Faggin designed the Z80 with two complete sets of registers, allowing operating systems and interrupt handlers to switch register contexts without saving and restoring registers in memory. He added an extended instruction set — block move and search instructions for memory operations, bit manipulation instructions, relative branch instructions that reduced program size. He included built-in dynamic RAM refresh circuitry, eliminating external refresh logic that designers had previously needed to add.

The Z80 entered a market where the 8080 was established but expensive. Zilog priced the Z80 competitively and delivered it in a 40-pin DIP package compatible with 8080 systems. It was faster, had more features, and cost less.

The result was one of the most successful microprocessors ever made. The Z80 powered the TRS-80 Model I (Radio Shack, 1977), the Sinclair ZX80 and ZX81 (1980, 1981), the ZX Spectrum (1982) — the machine that introduced personal computing to an entire generation of British users — the Osborne 1 portable computer, and countless CP/M-based business computers. The Z80 was the dominant processor of the CP/M ecosystem, the leading personal computing platform before the IBM PC. The Pac-Man arcade machine used a Z80. So did the MSX home computer standard, adopted across Asia and Europe. Millions of units were sold across thousands of applications.

The Z80 is still manufactured. As of the early 2020s, companies producing embedded control systems for industrial applications continue to use it. It has been in continuous production for nearly fifty years.

Synaptics and the Touchpad

After Zilog, Faggin went through several ventures before co-founding Synaptics in 1986 with Carver Mead of Caltech. Synaptics was initially focused on analog VLSI hardware for neural-network-inspired computation — building silicon circuits that performed pattern recognition by mimicking aspects of neural processing.

The neural network approach led to a more immediately commercial application: capacitive touch sensing. Synaptics developed the TouchPad — a flat, touch-sensitive surface that could track the position of a fingertip through the capacitive coupling between the finger and a grid of sensors beneath the surface. The device required no mechanical parts, no moving surfaces, no lubricant. It was thin, durable, and accurate.

The Synaptics TouchPad became the standard laptop pointing device through the 1990s and 2000s. Virtually every notebook computer sold between 1994 and the present has used either a Synaptics TouchPad or a competing device built on similar principles. The multi-touch sensing technology that Synaptics developed — detecting multiple simultaneous touch points — influenced the touchscreen technology that Apple used in the iPhone, though the relationship between Synaptics’ patents and Apple’s implementation was legally complex.

Consciousness and Later Life

In his seventies, Faggin turned to questions that might have seemed surprising from a microprocessor engineer: the nature of consciousness, the relationship between mind and matter, the limits of computational models of experience. He published a book, Silicon: From the Invention of the Microprocessor to the New Science of Consciousness (2021), in which he argued that the computational model of mind — the idea that consciousness is a form of information processing — was fundamentally inadequate to explain subjective experience. He proposed an alternative framework drawing on quantum mechanics and field theory.

The philosophical arguments in the book were contested. But the personal arc was coherent: a man who had spent fifty years building silicon devices that executed instructions had concluded that what mattered most — awareness, experience, the sense that something is happening — was not reducible to any computation he could design.

He had also, by that point, received most of the credit he had long deserved. Intel’s formal acknowledgment in 2009, the National Medal in 2010, and the ongoing recognition of the Z80’s historical significance meant that his name was associated, in the historical literature, with the inventions he had made.

Dead End: The Calculator Market

The 4004 was designed for a calculator application that largely vanished before the chip reached commercial maturity.

The full story of how the microprocessor transformed computing is told in The Integrated Circuit Revolution. The Intel context is covered in Andy Grove and Intel and Gordon Moore and Moore’s Law.

---

📚 Sources

• Federico Faggin: Silicon: From the Invention of the Microprocessor to the New Science of Consciousness (2021), Waterside Productions — worldcat.org/title/silicon
• Federico Faggin, Marcian E. Hoff, Stanley Mazor, and Masatoshi Shima: “The History of the 4004” — IEEE Micro, Vol. 16, No. 6 (December 1996) — doi.org/10.1109/40.546561
• Federico Faggin: “The MOS Silicon Gate Technology and the First Microprocessors” — La Rivista del Nuovo Cimento, Vol. 38, No. 12 (2015) — doi.org/10.1393/ncr/i2015-10119-7
• Michael S. Malone: The Intel Trinity (2014), HarperBusiness — worldcat.org/title/intel-trinity
• Masatoshi Shima: Oral History interview (the 4004 from the Japanese engineer’s perspective) — Engineering and Technology History Wiki, IEEE History Center — ethw.org/Oral-History:Masatoshi_Shima
• Robin Wilson: Sinclair and the Sunrise Technology: The Deconstruction of a Myth (2014) — worldcat.org/title/sinclair