Whirlwind I was a Cold War-era vacuum-tube computer developed by the MIT Servomechanisms Laboratory for the U.S. Navy.

Its development led directly to the Whirlwind II design used as the basis for the United States Air Force SAGE air defense system, and indirectly to almost all business computers and minicomputers in the 1960s,[3] particularly because of the mantra "short word length, speed, people.

"[4] During World War II, the U.S. Navy's Naval Research Lab approached MIT about the possibility of creating a computer to drive a flight simulator for training bomber crews.

They envisioned a fairly simple system in which the computer would continually update a simulated instrument panel based on control inputs from the pilots.

The Servomechanisms Lab in MIT building 32[5] conducted a short survey that concluded such a system was possible.

By 1947, Forrester and collaborator Robert Everett completed the design of a high-speed stored-program computer for this task.

This was simply not fast enough for their purposes, so Whirlwind included sixteen such math units, operating on a complete 16-bit word every cycle in bit-parallel mode.

Ignoring memory speed, Whirlwind ("20,000 single-address operations per second" in 1951)[7] was essentially sixteen times as fast as other machines.

The machine worked by passing in a single address with almost every instruction, thereby reducing the number of memory accesses.

Whirlwind operated much like a reverse Polish notation calculator in this respect; except there was no operand stack, only an accumulator.

Each step of the clock selected one or more signal lines in a diode matrix that enabled gates and other circuits on the machine.

[15][11]: 11.20–21  The project's budget was approximately $1 million a year, which was vastly higher than the development costs of most other computers of the era.

They were detected by the microphone, amplified, reshaped into the correct pulse shape, and sent back into the delay line.

Since a delay line held a defined number of bits, the frequency of the clock had to change with the temperature of the mercury.

The main memory was so late that the first experiments of tracking airplanes with live radar data were done using a program manually set into test storage.

Recognizing that this had the potential to be a data storage medium, Forrester obtained a workbench in the corner of the lab, and got several samples of the material to experiment with.

In the fall of 1949, Forrester enlisted graduate student William N. Papian to test dozens of individual cores, to determine those with the best properties.

The electrostatic memory design and production was summarily canceled, saving a good deal of money to be reallocated to other research areas.

[21]: 225 After connection to the experimental Microwave Early Warning (MEW) radar at Hanscom Field using Jack Harrington's equipment and commercial phone lines,[22] aircraft were tracked by Whirlwind I.

[23] The Cape Cod System subsequently demonstrated computerized air defence covering southern New England.

The Whirlwind II design for a larger and faster machine (never completed) was the basis for the SAGE air defense system IBM AN/FSQ-7 Combat Direction Central.

An effort was also started to convert the Whirlwind design to a transistorized form, led by Ken Olsen and known as the TX-0.

Even this version proved troublesome, and Olsen left in mid-project to start Digital Equipment Corporation (DEC).

The power to run the machine cost $2500 per month, and the Wolf Research and Development Corporation did work for the Air Force and Buckminster Fuller's World Game.

[25][26][27] Ken Olsen and Robert Everett saved the machine, which became the basis for the Boston Computer Museum in 1979.

[28] As of February 2009, a core memory unit is displayed at the Charles River Museum of Industry & Innovation in Waltham, Massachusetts.

The building which housed Whirlwind was until recently home to MIT's campus-wide IT department, Information Services & Technology and in 1997–1998, it was restored to its original exterior design.