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The microprocessor at 40--The birth of electronics

August 29, 2011

Jack Ganssle-August 29, 2011

The 4004 spawned the age of ubiquitous and cheap computing.

"We always overestimate the change that will occur in the next two years and underestimate the change that will occur in the next ten." —Bill Gates

If one human generation represents 20 years, as many sources suggest, two entire generations have been born into a world that has always had microprocessors. Two generations never knew a world where computers were rare and so expensive only large corporations or governments owned them. These same billions of people have no experience of a world where the fabric of electronics was terribly expensive and bulky, where a hand-held device could do little more than tune in AM radio stations.

In November, 1971, 40 years ago, Intel placed an ad in Electronic News introducing the 4004, the first microprocessor. "A micro-programmable computer on a chip!" the headline shouted. At the time in my first year of college, I was fortunate to snag a job as an electronics technician. None of the engineers I worked with believed the hype. Intel's best effort at the time had resulted in the 1103 DRAM, which stored just 1 kilobit of data. The leap to a computer on a chip seemed impossible. And so it turned out, as the 4004 needed a variety of extra components before it could actually do anything. But the 4004 heralded a new day in both computers and electronics.

The 4004's legacy wasn't that of a single-chip computer. That came within a few years. Rather, it spawned the age of ubiquitous and cheap computing. Yes, the era of the personal computer came a decade later and entirely as a result of the microprocessor, but the 4004 immediately ushered in the age of embedded systems. In the decade between the micro's invention and the first IBM PC, thousands, perhaps millions, of products hit the market with embedded intelligence.

Forty years ago few people had actually seen a computer; today, no one can see one, to a first approximation, as the devices have become so small.

Embedded Systems Design magazine and the entire embedded systems industry that employs so many of us couldn't exist without the microprocessor. In the four decades since its birth, everything we know about electronics has changed. And so, for this and the next three issues of this magazine, I will devote this column to a look back at the story of this astonishing invention.

The history of the micro is really the story of electronics, which is the use of active elements (such as transistors, tubes, diodes) to transform signals. And the microcomputer is all about using massive quantities of active elements. But electrical devices—even radios and TV—existed long before electronics.

Happy Birthday, 4004
Jack Ganssle's series in honor of the 40th anniversary of the 4004 microprocessor.

Part 1: The microprocessor at 40--The birth of electronics
The 4004 spawned the age of ubiquitous and cheap computing.

Part 2: From light bulbs to computers 
From Patent 307,031 to a computer laden with 100,000 vacuum tubes, these milestones in first 70 years of electronics made the MCU possible.

Part 3: The semiconductor revolution
In part 3 of Jack's series honoring the 40th anniversary of the microprocessor, the minis create a new niche—the embedded system.


Mother Nature was the original progenitor of electrical systems. Lightning is merely a return path in a circuit composed by clouds and the atmosphere. Some think that bit of natural wiring may have created life on this planet. Miller and Urey created amino acids in 1952 using simulated high-energy discharges. But it took four billion years after Earth formed before Homo sapiens arrived, and then a little longer until Ben Franklin and others in France found, in 1752, that lightning and sparks are the same stuff. Hundreds of years later kids repeat this fundamental experiment when they shuffle across a carpet and zap their unsuspecting friends and parents (the latter usually holding something expensive and fragile).

Other natural circuits include the electrocytes found in electric eels. Somewhat battery-like, they're composed of thousands of individual "cells," each of which produces 0.15 volts. It's striking how the word "cell" is shared by biology and electronics, unified with particular emphasis in the electrocyte.

Alessandro Volta was probably the first to understand that these organic circuits used electricity. Others, notably Luigi Galvani (after whom the galvanic cell is named) mistakenly thought some sort of biological fluid was involved. Volta produced the first artificial battery, although some scholars think that the Persians may have invented one thousands of years earlier.

About the same time others had built Leyden jars—early capacitors. A Leyden jar is a glass bottle with foil on the surface and an inner rod. I suspect it wasn't long before natural philosophers (proto-scientists) learned to charge the jar and zap their kids. Polymath Ben Franklin, before he got busy with forming a new country and all that, wired jars in series and called the result a "battery," from the military term, which is the first use of that word in the electrical arena.

Many others contributed to the understanding of the strange effects of electricity. Joseph Henry showed that wire coiled tightly around an iron core greatly improved the electromagnet. That required insulated wire long before Digikey existed, so he reputedly wrapped silk ripped from his long-suffering wife's wedding dress around the bare copper. This led directly to the invention of the telegraph.

Wives weren't the only to suffer in the long quest to understand electricity. In 1746 Jean-Antoine Nollet wired 200 monks in a mile-long circle and zapped them with a battery of Leyden jars. One can only imagine the reaction of the circuit of clerics, but their simultaneous jerking and no doubt not-terribly pious exclamations demonstrated that electricity moved very quickly indeed.

It's hard to pin down the history of the resistor, but Georg Ohm published his findings that we now understand as Ohm's Law in 1827. So the three basic passive elements—resistor, capacitor, and inductor—were understood at least in general form in the early 19th century. Amazingly it wasn't till 1971 that Leon Chua realized a fourth device, the memresistor, was needed to have a complete set of components, and another four decades elapsed before one was realized.

Michael Faraday built the first motors in 1821, but it wasn't until the 1860s that James Maxwell figured out the details of the relationship between electricity and magnetism; 150 years later his formulas still torment electrical engineering students. Faraday's investigations into induction also resulted in his creation of the dynamo. It's somehow satisfying that this genius completed the loop, building both power consumers and power producers.

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