The RCA Selectron -- Background of memories for digital computers

" water buffalo...two water buffalo...three waterbu RUN! RUN! TIGER! TIGER!,, just a shadow, false alarm. Where was I? Um, water, one water buffalo...two water buffalo....

When the first hominids attempted dominion over the world there were two functions, among many others, that were necessary: Quantizing and Memory. Tools and mnemonics were soon in use. "One pebble represents one water buffalo. My pile of pebbles shows how many waterbuffalo I saw today." Abstraction and analogy were added to the tool kit.

The abacus was a nice step forward in that the pebbles were constrained on a bamboo rod, minimizing loss and subsequent error. Additionally, a concept was embraced that not all pebbles carried the same meaning. Some pebbles can represent a larger quantity of items than other pebbles.

Leap to World War II. Crypto, Bletchley Park, The Institute for Advanced Study, digital computers, 4k-bit memory tubes. "Wuzzah? 4096-bit digital memories in the 1940s?" Yup. "4096 bits, with decoding, in a vacuum tube?" Yup. "Let me get this straight, 4k RAM in one package 30 years before the Mostek MK4096 4k-bit chip?" Well, sorta: The Mostek part was a DRAM, and needed external support circuitry to be refreshed every two milliseconds to retain the data. Selectrons were static devices. But we are getting ahead of ourselves.

Two needs of war drove the development of the electronic computer: calculating artillery geometry and deciphering encrypted documents. Guns and spies.

Guns: You're here, the target is there, and you want to deliver a projectile to the target. You know the projectile mass, the distance, the difference in elevation, the direction and strength of any wind and the wind resistance of the projectile. And how much energy (powder) you have to launch it. You could calculate where to point your gun -- direction and height -- but it would be so much nicer to just look it up in a table. One where the calculations were carefully performed in a calm office environment rather than hastily done out in the rainy weather while other folks are trying to deliver their projectiles to you.

Spies: Guess what the string of nonsensical letters transmitted over the radio mean. They mean sumthin' to the other guys. Guess? Or run through all the combinations of replacements looking for patterns you know exist from previous messages, and from knowledge about the way the message was encoded. There has to be a mathematical way to do this.... There are only so many types of guns and ammo, but brand new messages are arriving all the time. This makes the gun calculations seem easy.

The United States military pushed development of calculating aids for artillery ballistics calculations; The result was ENIAC. The British efforts to automate the process of code breaking resulted in Colossus and other machines. If necessity really is the mother of invention, WWII initiated the information age.

After the war the Princeton, New Jersey based Institue for Advanced Study realized that a computer might be a useful tool. Seeing as none were commercially available it was decided to build their own. This was a remarkable decision on several levels, not the least being that the IAS was not known for a "roll up your sleeves and get dirty" mindset. Think "Albert Einstein" and not "Marie Curie." IAS folks were more likely to suffer from the ravages of chalkboard dust than radium poisoning, so building their own machine was a big change.

The IAS's John von Neumann headed the computer development program and was quick to enlist the aid of the best and the brightest...and most powerful post-war America had to offer.

David Sarnoff's Radio Corporation of America had just relocated its laboratories to Princeton, albeit just the other side of nearby U. S. Route 1. RCA Laboratories "volunteered" to develop the "memory organ" for Von Neumann's machine. (The somewhat "slimy and creepy" biological terminology for the elements of computing devices used during the formative years of electronic computing appear more alien and humorous in the modern context. Early work on computing was, in some circles, leaning away from developing overblown adding machines and toward the goals of harnessing "electric brains" which could mimic the human mind. But I digress....) At the behest of General Sarnoff, the Labs set one of their brightest teams, under the supervision of Vladimir Zworykin of television development fame, to the task. Swiss born Jan Rajchman had recently completed work on the Computron, part of a crash program during the war to develop digital computers to aim anti-aircraft guns. While the Computron -- co-developed with the brilliant engineer Richard L. Snyder, Jr. who had recently left RCA and joined the IAS -- was hailed as technologically amazing it suffered from being both too early (and thus not recognized as being useful) and too advanced to be practically built with the existing state of the art in electron tube engineering.

Could a memory device be created with the technology developed for the abandoned Computron? That was the plan. The Selectron -- A Selective Electrostatic Storage Tube -- began as a model of simplicity in both theory and implementation. With the resources of a modern research laboratory and the leading electronics empire devoting experts and resources a clever and useful memory device began to emerge.

To be continued...