IAS machine

IAS machine

The IAS machine is the computer that got copied by the entire world. Built at Princeton's Institute for Advanced Study under John von Neumann — with Herman Goldstine and Arthur Burks from the ENIAC team and Julian Bigelow as chief engineer — it ran fully from 10 June 1952, and its purpose was almost more important than its hardware: to prove the stored-program concept worked, in the open, with the plans distributed free to anyone who wanted to build one.^[1]

The machine itself was a work of extreme economy: a 40-bit word holding two 20-bit instructions, 1,024 words of memory, about 1,700 tubes, one thousand pounds — and asynchronous, with no central clock at all: each instruction simply started when the last one finished. Its memory was a salvage operation — the design called for 40 exotic RCA Selectron storage tubes that never materialized, so Bigelow's team substituted Williams tubes: forty CRTs storing bits as electrostatic patterns, plus a forty-first displaying the memory's state. Among the era's binary machines it was also an early fully parallel design — all 40 bits of a word moved at once.^[2]

A computer with forty children

The IAS's real product was its documentation. Schools, labs, and companies worldwide took the plans and built their own — a family tree of one-off machines historians just call "IAS machines": MANIAC at Los Alamos, ILLIAC at Illinois, JOHNNIAC at RAND (the machine that would later host JOSS — fitting, since IAS engineer Willis Ware went on to RAND and wrote the memo that started JOSS), BESM in Moscow, WEIZAC in Israel, DASK in Copenhagen, SARA at SAAB — and, at industrial scale, the IBM 701, the first IBM commercial scientific computer. A generation of national computing programs bootstrapped from one Princeton machine's blueprints.^[3]

Where it sits

The IAS machine was never a product and never wanted to be — it was a demonstration that the idea worked, packaged so well that the idea spread by photocopy. It ran until July 1958; the Smithsonian owns it now. Every "von Neumann architecture" machine since is, genealogically, a descendant of forty humming CRT tubes at Princeton.

Check your understanding

• Why was the IAS machine built — and what was done with its plans?
• What made its timing unusual among early computers?
• What storage technology was it designed around, and what did it actually use?
• Name three machines in the IAS clone family.