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Whirlwind (computer)
Encyclopedia
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
was developed at the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
. It is the first computer that operated in real time, used video displays for output, and the first that was not simply an electronic replacement of older mechanical systems. Its development led directly to the United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
's Semi Automatic Ground Environment
Semi Automatic Ground Environment
The Semi-Automatic Ground Environment was an automated control system for tracking and intercepting enemy bomber aircraft used by NORAD from the late 1950s into the 1980s...
(SAGE) system, and indirectly to almost all business computers and minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
s in the 1960s.
Background
During World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, the U.S. Navy approached MIT about the possibility of creating a computer to drive a flight simulator
Flight simulator
A flight simulator is a device that artificially re-creates aircraft flight and various aspects of the flight environment. This includes the equations that govern how aircraft fly, how they react to applications of their controls and other aircraft systems, and how they react to the external...
for training bomber
Bomber
A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...
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. Unlike older systems like the Link Trainer
Link Trainer
The term Link Trainer, also known as the "Blue box" and "Pilot Trainer" is commonly used to refer to a series of flight simulators produced between the early 1930s and early 1950s by Ed Link, based on technology he pioneered in 1929 at his family's business in Binghamton, New York...
, the system they envisioned would have a considerably more realistic aerodynamics
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
model that could be adapted to any type of plane. This was an important consideration at the time, when many new designs were being introduced into service.
A short study by the MIT Servomechanisms Laboratory concluded that such a system was certainly possible. The Navy decided to fund development under Project Whirlwind, and the lab placed Jay Forrester in charge of the project. They soon built a large analog computer
Analog computer
An analog computer is a form of computer that uses the continuously-changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved...
for the task, but found that it was inaccurate and inflexible. Solving these problems in a general way would require a much larger system, perhaps one so large as to be impossible to construct.
In 1945 Perry Crawford, another member of the MIT team, saw a demonstration of ENIAC
ENIAC
ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....
and suggested that a digital computer was the solution. Such a machine would allow the accuracy of the simulation to be improved with the addition of more code in the computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
, as opposed to adding parts to the machine. As long as the machine was fast enough, there was no theoretical limit to the complexity of the simulation.
Up until this point all computers constructed were dedicated to single tasks, run in batch mode. A series of inputs were set up in advance and fed into the computer, which would work out the answers and print them. This was not appropriate for the Whirlwind system, which needed to operate continually on an ever-changing series of inputs. Speed became a major issue, whereas with other systems it simply meant waiting longer for the printout, with Whirlwind it meant seriously limiting the amount of complexity the simulation could include.
Design and construction
By 1947, Forrester and collaborator Robert EverettRobert Everett (computer science)
Robert R. Everett is a computer scientist. He is an honorary board member of the Mitre Corporation.In 1945 he worked with Jay Forrester on the Whirlwind project, one of the first real time electronic computers...
completed the design of a high-speed stored-program computer for this task. Most computers of the era operated in bit-serial mode
Serial computer
A serial computer is typified by internally operating on one bit or digit for each clock cycle. Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating magnetic devices were usually serial computers....
, using single-bit arithmetic and feeding in large words, often 48 or 60 bits in size, one bit at a time. 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 was essentially sixteen times as fast as other machines. Today almost all CPUs do arithmetic in "bit-parallel" mode.
The word size was selected after some deliberation. The machine worked by passing in a single address with almost every instruction, thereby reducing the number of memory accesses. For operations with two operands, adding for instance, the "other" operand was assumed to be the last one loaded. Whirlwind operated much like a reverse Polish notation
Reverse Polish notation
Reverse Polish notation is a mathematical notation wherein every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position. It is also known as Postfix notation and is parenthesis-free as long as operator arities are fixed...
calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
in this respect; except there was no operand stack, only an accumulator
Accumulator (computing)
In a computer's central processing unit , an accumulator is a register in which intermediate arithmetic and logic results are stored. Without a register like an accumulator, it would be necessary to write the result of each calculation to main memory, perhaps only to be read right back again for...
. The designers felt that 2048 words of memory would be the minimum usable amount, requiring 11 bits to represent an address, and that 16 to 32 instructions would be the minimum for another 5 bits — and so it was 16-bits. Nevertheless the small word size led John von Neumann
John von Neumann
John von Neumann was a Hungarian-American mathematician and polymath who made major contributions to a vast number of fields, including set theory, functional analysis, quantum mechanics, ergodic theory, geometry, fluid dynamics, economics and game theory, computer science, numerical analysis,...
to conclude the machine would be worthless.
The Whirlwind design incorporated a control store
Control store
A control store is the part of a CPU's control unit that stores the CPU's microprogram. It is usually accessed by a microsequencer. Early control stores were implemented as a diode-array accessed via address decoders, a form of read-only memory. This tradition dates back to the program timing...
driven by a master clock. Each step of the clock selected a signal line in a diode matrix
Diode matrix
A diode matrix is a two-dimensional grid of wires, where each "intersection" where one row crosses over another either has a diode connecting them, or the wires are isolated from each other....
that enabled gates and other circuits on the machine. A special switch directed signals to different parts of the matrix to implement different instructions. The design inspired Maurice Wilkes to develop the concept of microprogramming
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
.
Construction of the machine started the next year, an effort that employed 175 people including 70 engineers and technicians. Whirlwind took 3 years to build and first went online on April 20, 1951. The project's budget was $1 million a year, and after three years the Navy had lost interest. However, during this time the Air Force had become interested in using computers to help the task of ground controlled interception
Semi Automatic Ground Environment
The Semi-Automatic Ground Environment was an automated control system for tracking and intercepting enemy bomber aircraft used by NORAD from the late 1950s into the 1980s...
, and the Whirlwind was the only machine suitable to the task. They took up development under Project Claude.
The core of the machine
The speed of the original design (20 KIPS) turned out to be too slow to be very useful, and most of the problem was attributed to the fairly slow speed of the Williams tubeWilliams tube
The Williams tube or the Williams-Kilburn tube , developed in about 1946 or 1947, was a cathode ray tube used to electronically store binary data....
s for main memory of 256 words. Forrester started looking at replacements, first using magnetic tape formed into spirals, even at one time considering using a 3-D array of neon lamp
Neon lamp
A neon lamp is a miniature gas discharge lamp that typically contains neon gas at a low pressure in a glass capsule. Only a thin region adjacent to the electrodes glows in these lamps, which distinguishes them from the much longer and brighter neon tubes used for signage...
s, and eventually creating core memory.
Before its conversion to core memory, the machine could add two numbers in 49 μs and multiply them in 61 μs. After conversion, addition time was 8 μs, multiplication 25.5 μs, and a division 57 μs. Speed was roughly doubled (40 KIPS) when the new version was completed in 1953.
The Cape Cod System and Whirlwind II
The Cape Cod System was designed to demonstrate a computerized air defence system, covering southern New EnglandNew England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
. Signals from three long range (AN/FPS-3) radars, eleven gap-filler radars, and three height-finding radars were converted from analog to digital format and transmitted over telephone line
Telephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
s to the Whirlwind I computer in Cambridge, Massachusetts
Cambridge, Massachusetts
Cambridge is a city in Middlesex County, Massachusetts, United States, in the Greater Boston area. It was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Cambridge is home to two of the world's most prominent...
. The Cape Cod System verified that the new core-based machine was fast enough for use in SAGE
Semi Automatic Ground Environment
The Semi-Automatic Ground Environment was an automated control system for tracking and intercepting enemy bomber aircraft used by NORAD from the late 1950s into the 1980s...
, and an industrial effort was started in order to mass-produce the AN/FSQ-7
AN/FSQ-7
The AN/FSQ-7 was a computer model developed and built in the 1950s by IBM in partnership with the US Air Force. Fifty-two were built and used for command and control functions for the Semi Automatic Ground Environment air-defense system...
computers for this role.
After Whirlwind was completed and running, a design for a larger and faster machine to be called Whirlwind II was begun. But the design soon became too much for MIT's resources. It was decided to shelve the Whirlwind II design without building it and concentrate MIT's resources on programming and applications for the original machine, now called Whirlwind I. IBM based their production designs, the AN/FSQ-7, on the stillborn Whirlwind II. Thus the AN/FSQ-7 is sometimes incorrectly referred to as "Whirlwind II", even though they were not the same machine or design.
Legacy
Whirlwind I ran in a support role for SAGE until June 30, 1959. A member of the project team, Bill Wolf, then rented the machine for a dollar a year until 1973. Ken OlsenKen Olsen
Kenneth Harry Olsen was an American engineer who co-founded Digital Equipment Corporation in 1957 with colleague Harlan Anderson.-Background:...
and Robert Everett
Robert Everett (computer science)
Robert R. Everett is a computer scientist. He is an honorary board member of the Mitre Corporation.In 1945 he worked with Jay Forrester on the Whirlwind project, one of the first real time electronic computers...
then saved the machine from the scrap heap and it became the basis for the Digital Computer Museum, which would later become The Computer Museum
The Computer Museum, Boston
The Computer Museum was a Boston, Massachusetts museum that opened in 1979 and operated in three different locations until 1999. It was once referred to as TCM and is sometimes called the Boston Computer Museum....
on Boston's Museum Wharf. Today it is in the collection of the Computer History Museum
Computer History Museum
The Computer History Museum is a museum established in 1996 in Mountain View, California, USA. The Museum is dedicated to preserving and presenting the stories and artifacts of the information age, and exploring the computing revolution and its impact on our lives.-History:The museum's origins...
in Mountain View, California, and a portion of the machine is currently on display. As of February 2009, one of Whirlwind's core memory units is on display at the Charles River Museum of Industry
Charles River Museum of Industry
Charles River Museum of Industry is a museum located near the intersection of the Charles River and what is now Moody Street in Waltham, Massachusetts. The building was originally a textile mill for the Boston Manufacturing Company, which the museum claims to have been "America's First Factory" in...
in Waltham, Massachusetts
Waltham, Massachusetts
Waltham is a city in Middlesex County, Massachusetts, United States, was an early center for the labor movement, and major contributor to the American Industrial Revolution. The original home of the Boston Manufacturing Company, the city was a prototype for 19th century industrial city planning,...
.
The Whirlwind used approximately 5000 vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s. An effort was also started to convert the Whirlwind design to a transistorized form, led by Ken Olsen
Ken Olsen
Kenneth Harry Olsen was an American engineer who co-founded Digital Equipment Corporation in 1957 with colleague Harlan Anderson.-Background:...
and known as the TX-0
TX-0
The TX-0, for Transistorized Experimental computer zero, but affectionately referred to as tixo , was an early fully transistorized computer and contained a then-huge 64K of 18-bit words of magnetic core memory. The TX-0 was built in 1955 and went online in 1956 and was used continually through the...
. TX-0 was very successful and plans were made to make an even larger version known as TX-1. However this project was far too ambitious and had to be scaled back to a smaller version known as TX-2
TX-2
The MIT Lincoln Laboratory TX-2 computer was the successor to the Lincoln TX-0 and was known for its role in advancing both artificial intelligence and human-computer interaction.- Specifications :...
. Even this version proved troublesome, and Olsen left in mid-project to start Digital Equipment Corporation
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
(DEC). DEC's PDP-1
PDP-1
The PDP-1 was the first computer in Digital Equipment Corporation's PDP series and was first produced in 1960. It is famous for being the computer most important in the creation of hacker culture at MIT, BBN and elsewhere...
was essentially a collection of TX-0 and TX-2 concepts in a smaller package.
MIT's Barta Building (now building N42) which housed Whirlwind during the project's lifetime, is now home to MIT's campus-wide IT department, Information Services & Technology. In 1997-8, the building was restored to its original exterior design, and can be found at 211 Massachusetts Ave, Cambridge.
See also
- History of computing hardwareHistory of computing hardwareThe history of computing hardware is the record of the ongoing effort to make computer hardware faster, cheaper, and capable of storing more data....
- Laning and Zierler systemLaning and Zierler systemThe Laning and Zierler system was one of the first operating algebraic compilers, that is, a system capable of accepting mathematical formulae in algebraic notation and producing equivalent machine code. It was implemented in 1954 for the MIT WHIRLWIND by J. Halcombe Laning and Neal Zierler...
- System DynamicsSystem dynamicsSystem dynamics is an approach to understanding the behaviour of complex systems over time. It deals with internal feedback loops and time delays that affect the behaviour of the entire system. What makes using system dynamics different from other approaches to studying complex systems is the use...
- Jay W. Forrester
External links
- Oral history interview with Fernando J. Corbató at Charles Babbage InstituteCharles Babbage InstituteThe Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....
, University of Minnesota. Corbató discusses computer science research at the Massachusetts Institute of Technology (MIT), including the development of the Whirlwind computer. - Oral history interview with Douglas T. Ross at Charles Babbage Institute, University of Minnesota. Ross recounts some of his working on MIT's Whirlwind computer in the 1950s. He reports on his first use of Whirlwind for airborne fire control problems. Soon after that the Whirlwind was used for the Cape Cod early warning system, a precursor to the SAGE Air Defense System. Ross describes improvements made to Whirlwind, including the first light penLight penA light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy...
and photoelectric tape reader. Ross also discusses some of the programs he wrote or used on Whirlwind. - Computer Structures: Readings & Examples — The Whirlwind I computer
- Overview of the Lincoln Laboratory Ballistic Missile Defense Program
- Whirlwind documentation on Bitsavers.org
- Compaq donates artifacts