The microprocessor at 40-The birth of electronics -

The microprocessor at 40–The birth of electronics


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.

None of these inventions and discoveries affected the common person until the commercialization of the telegraph. Many people contributed to that device, but Samuel Morse is the most well-known. He and Alfred Vail also critically develop a coding scheme—Morse Code—that allowed long messages to be transmitted over a single circuit, rather like modern serial data transmission. Today's Morse code resembles the original version but with some substantial differences. SOS was dit-dit-dit dit-dit dit-dit-dit instead of today's dit-dit-dit dah-dah-dah dit-dit-dit.

The telegraph may have been the first killer app. Within a decade of its commercialization, over 20,000 miles of telegraph wire had been strung in the U.S., and the cost to send messages followed a Moore's Law-like curve.

The oceans were great barriers in these pre-radio days, but through truly heroic efforts Cyrus Field and his associates laid the first transatlantic cable in 1857. Consider the problems faced: with neither active elements nor amplifiers a wire 2,000 miles long, submerged thousands of feet below the surface, had to faithfully transmit a signal. Two ships set out and met mid-ocean to splice their respective ends together. Sans GPS, they relied on celestial sights to find each other. Without radio-supplied time ticks, those sights were suspect (four seconds of error in time can introduce a mile of error in the position).

William Thomson, later Lord Kelvin, was the technical brains behind the cable. He invented a mirror galvanometer to sense the miniscule signals originating so far away. Thomson was no ivory-tower intellect. He was an engineer (at that point in life) who got his hands dirty. He sailed on the cable-laying expeditions and innovated solutions to the problems encountered.

While at a party celebrating the success, Field was notified that the cable had failed. He didn't spoil the fun with that bit of bad news. It seems a zealous engineer thought if a little voltage was good, 2,000 would be better. The cable fried. This was not the first nor the last time an engineer destroyed a perfectly functional piece of equipment in an effort to “improve” it.

Amazingly, radio existed in those pre-electronic days. The Titanic's radio operators sent their dit-dit-dit dah-dah-dah dit-dit-dit with a spark gap transmitter, a very simple design that used arcing contacts to stimulate a resonant circuit. The analogy to a modern AM transmitter isn't too strained: today, we'd use a transistor switching rapidly to excite an LC network. The Titanic's LC components resonated as the spark rapidly formed, creating a low-impedance conductive path, and extinguished. The resulting emission is not much different from the EMI caused by lightning. The result was a very ugly wide-bandwidth signal, and the legacy of calling shipboard radio operators “sparks.”

TV, of a sort, was possible in the late 1800s, although it's not clear if it was actually implemented. Around 1884, Paul Nipkow conceived of a spinning disk with a series of holes arranged in a spiral to scan a scene. In high school I built a Nipkow Disk, although used a photomultiplier to sense the image and send it to TTL logic that reconstructed the picture on an oscilloscope. The images were crude, but recognizable.

The next killer app was the telephone, another invention with a complex and checkered history. But wait—there's a common theme here, or even two. What moved these proto-electronic products from curiosity to wide acceptance was the notion of communications. Today it's SMS and social networking; in the 19th century it was the telegraph and telephone. But it seems that as soon as any sort of communications tech was invented, from smoke signals to the Internet, people were immediately as enamored with it as any of today's cell-phone obsessed teenagers.

The other theme is that each of these technologies suffered from signal losses and noise. They all cried out for some new discovery that should amplify, shape and improve the flow of electrons. Happily, in the last couple of decades of the 1800s inventors were scrambling to perfect such a device. They just didn't know it.

Jack Ganssle () is a lecturer and consultant specializing in embedded systems development. He has been a columnist with Embedded Systems Design and for over 20 years. For more information on Jack, click here.

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