The semiconductor revolution

October 28, 2011

Jack Ganssle-October 28, 2011

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

We're on track, by 2010, for 30-gigahertz devices, 10 nanometers or less, delivering a tera-instruction of performance.   —Pat Gelsinger, Intel, 2002

We all know how in 1947 Shockley, Bardeen, and Brattain invented the transistor, ushering in the age of semiconductors. But that common knowledge is wrong. Julius Lilienfeld patented devices that resembled field-effect transistors (although they were based on metals rather than modern semiconductors) in the 1920s and 30s (he also patented the electrolytic capacitor). Indeed, the United States Patent and Trademark Office rejected early patent applications from the Bell Labs boys, citing Lilienfeld's work as prior art.

Semiconductors predated Shockley et al by nearly a century. Karl Ferdinand Braun found that some crystals conducted current in only one direction in 1874. Indian scientist Jagadish Chandra Bose used crystals to detect radio waves as early as 1894, and Greenleaf Whittier Pickard developed the cat's whisker diode. Pickard examined 30,000 different materials in his quest to find the best detector, rusty scissors included. Like thousands of others, I built an AM radio using a galena cat's whisker and a coil wound on a Quaker Oats box as a kid, though by then everyone was using modern diodes.

Click on image to enlarge.
For image rights, see Wikipedia's entry on "cat's-whisker detector."

As I noted last month, RADAR research during World War II made systems that used huge numbers of vacuum tubes both possible and common. But that work also led to practical silicon and germanium diodes. These mass-produced elements had a chunk of the semiconducting material that contacted a tungsten whisker, all encased in a small cylindrical cartridge. At assembly time workers tweaked a screw to adjust the contact between the silicon or germanium and the whisker. With part numbers like 1N21, these were employed in the RADAR sets built by MIT's Rad Lab and other vendors. Volume 15 of MIT's Radiation Laboratory Series, titled "Crystal Rectifiers," shows that quite a bit was understood about the physics of semiconductors during World War II. The title of volume 27 tells a lot about the state of the art of computers: "Computing Mechanisms and Linkages."

Early tube computers used crystal diodes. Lots of diodes: the ENIAC had 7,200, Whirlwind twice that number. I have not been able to find out anything about what types of diodes were used or the nature of the circuits, but imagine an analog with 1960s-era diode-transistor logic.

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.

While engineers were building tube-based computers, a team lead by William Shockley at Bell Labs researched semiconductors. John Bardeen and Walter Brattain created the point contact transistor in 1947, but did not include Shockley's name on the patent application. Shockley, who was as irascible as he was brilliant, in a huff went off and invented the junction transistor. One wonders what wonder he would have invented had he been really slighted.

Point contact versions did go into production. Some early parts had a hole in the case; one would insert a tool to adjust the pressure of the wire on the germanium. So it wasn't long before the much more robust junction transistor became the dominant force in electronics. By 1953 over a million were made; four years later production increased to 29 million. That's exactly the same number as a single Pentium III used in 2000.

The first commercial part was probably the CK703, which became available in 1950 for $20 each, or $188 in today's dollars.

Meanwhile tube-based computers were getting bigger and hotter and were sucking ever more juice. The same University of Manchester that built the Baby and Mark 1 in 1948 and 1949 got a prototype transistorized machine going in 1953, and the full-blown model running two years later. With a 48- (some sources say 44) bit word, the prototype used only 92 transistors and 550 diodes! Even the registers were stored on drum memory, but it's still hard to imagine building a machine with so few active elements. The follow-on version used just 200 transistors and 1,300 diodes, still no mean feat. (Both machines did employ tubes in the clock circuit.) But tube machines were more reliable as this computer ran about an hour and a half between failures. Though deadly slow it demonstrated a market-changing feature: just 150 watts of power were needed. Compare that to the 25 KW consumed by the Mark 1. IBM built an experimental transistorized version of their 604 tube computer in 1954; the semiconductor version ate just 5% of the power needed by its thermionic brother. (The IBM 604 was more calculator than computer.)

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