Institute for Advanced Study I | June 10, 1952

 

The IAS machine is the first electronic computer built at the Institute for Advanced Study (IAS) in Princeton, New Jersey. It is sometimes referred to as the von Neumann machine because the design was documented in a paper edited by John von Neumann. The construction of the computer began in 1946 under his supervision and was completed in 1951. Its general structure is known as the von Neumann architecture, although the actual design and implementation were carried out by others. The computer is part of the collection at the Smithsonian National Museum of American History but is not currently on display.

In front of the IAS machine, J. Robert Oppenheimer and John von Neumann are seen together. In May 1946, Julian Bigelow was hired as the chief engineer. Other contributors to the project included Hewitt Crane, Herman Goldstine, Gerald Estrin, Arthur Burks, George W. Brown, and Willis Ware. The machine operated in a limited capacity during the summer of 1951 and became fully operational on June 10, 1952. It continued to operate until July 15, 1958.

The IAS machine is a binary computer that uses 40-bit words and can store two 20-bit instructions in each word. It had a memory of 1,024 words (approximately 5 kilobytes by modern standards). Negative numbers were represented in two's complement format, and it featured two general-purpose registers: the Accumulator (AC) and the Multiplier/Quotient (MQ). The machine used 1,700 vacuum tubes (triodes: 6J6, 5670, 5687, along with a few diodes: 6AL5 type, 150 pentodes to drive the memory CRT, 40 Williams tube memories, and one CRT: 5CP1A type for status monitoring). The memory was originally designed to use about 2,300 RCA Selectron vacuum tubes, but due to development issues with this complex tube, it was changed to Williams tubes.

The machine weighed approximately 1,000 pounds (450 kg).

Asynchronous in nature, it did not have a central clock to regulate the timing of instructions. A subsequent instruction did not start until the previous one had finished. The time for addition was 62 microseconds, while multiplication took 713 microseconds.

Some claim that the IAS machine was the first design to mix programs and data in a single memory, but this had already been implemented by the Manchester Baby in 1948. The Soviet MESM also became operational before the IAS machine.

Von Neumann proposed the requirement that instructions, data, and input/output should all be accessed through the same bus, which later became known as the von Neumann bottleneck.