Editing Whirlwind I (section)

===Design and construction===
By 1947, Forrester and collaborator [[Robert Everett (computer scientist)|Robert Everett]] completed the design of a high-speed [[stored-program computer]] for this task. Most computers of the era operated in [[serial computer|''bit-serial'' mode]], 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 ("20,000 single-address operations per second" in 1951)<ref>{{Cite journal |author-last=Everett |author-first=R. R. |title=The Whirlwind I computer |journal=Papers and Discussions Presented at the December 10–12, 1951, Joint AIEE-IRE Computer Conference: Review of Electronic Digital Computers |year=1951 |publisher=[[Association for Computing Machinery|ACM]] |pages=70–74 |doi=10.1145/1434770.1434781 |s2cid=14937316 |url=http://research.microsoft.com/en-us/um/people/gbell/Computer_Structures__Readings_and_Examples/00000157.htm |access-date=2013-08-12|doi-access=free }}</ref> was essentially sixteen times as fast as other machines. Today, almost all [[Central processing unit|CPU]]s perform 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]] [[calculator]] in this respect; except there was no operand stack, only an [[accumulator (computing)|accumulator]]. 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 five bits&nbsp;— and so it was 16 bits.<ref name="EverettSwain">{{Cite report |url=http://www.bitsavers.org/pdf/mit/whirlwind/R-series/R-127_Whirlwind_I_Computer_Block_Diagrams_Volume_1_Sep47.pdf |title=Report R-127 Whirlwind I Computer Block Diagrams |author-first1=R. R. |author-last1=Everett |author-first2=F. E. |author-last2=Swain |publisher=Servomechanisms Laboratory, MIT |date=September 4, 1947 |page=2 |archive-url=https://web.archive.org/web/20060908172605/http://www.cs.stthomas.edu/faculty/resmith/papers/WhirlwindR-127.pdf |archive-date=2006-09-08 |access-date=2012-12-31 |quote=The basic impulse rate for operation of the computer will be one megacycle. […] The Whirlwind I Computer is being planned for a storage capacity of 2,048 numbers of 16 binary digits each.}}</ref>

The Whirlwind design incorporated a [[control store]] driven by a master clock. Each step of the clock selected one or more signal lines in a [[diode matrix]] that enabled gates and other circuits on the machine. A special switch directed signals to different parts of the matrix to implement different instructions.{{Citation needed|date=July 2009}}  In the early 1950s, Whirlwind I "would crash every 20 minutes on average."<ref>{{Citation |format=pdf transcript of vocal recording |title=An Interview With Fernando J. Corbató |date=14 November 1990 |url=http://purl.umn.edu/107230 |access-date=2013-08-12|last1=Corbató |first1=F. J. }}</ref>

Whirlwind construction started in 1948, an effort that employed 175 people, including 70 engineers and technicians. The use of carry save multiplication appears to have been first introduced in the Whirlwind computer in the late 1940s.<ref>{{cite book |title=Computer Architecture and Organization |last=HAYES |first=JOHN.P |isbn=0-07-027363-4 |year=1978 |page=190 |publisher=McGraw-Hill International Book Company }}</ref> In the third quarter of 1949, the computer was advanced enough to solve an equation and display its solution on an oscilloscope,<ref name="ProjectWhirlwind" />{{Rp|11.13}}<ref name=":0">{{Cite journal|date=1950-01-01|title=2. Whirlwind I|url=https://apps.dtic.mil/sti/citations/AD0694596|archive-url=https://web.archive.org/web/20210311004157/http://www.dtic.mil/docs/citations/AD0694596|url-status=live|archive-date=March 11, 2021|journal=Digital Computer Newsletter|language=en|volume=2|issue=1|pages=1–2}}</ref> and even for the first animated and interactive computer graphic game.<ref>{{Cite book|url=https://books.google.com/books?id=6a8_AAAAQBAJ&q=Whirlwind+bouncing+ball&pg=PA81|title=The History of Visual Magic in Computers: How Beautiful Images are Made in CAD, 3D, VR and AR|last=Peddie|first=Jon|date=2013-06-13|publisher=Springer Science & Business Media|isbn=9781447149323|pages=81–82|language=en}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=JshzAAAAIAAJ&q=Whirlwind+charlie+adams|title=Computer graphics; utility, production, art|date=1967|publisher=Thompson Book Co.|pages=106|language=en}}</ref> Finally Whirlwind "successfully accomplished digital computation of interception courses" on April 20, 1951.<ref>{{Cite book|url=https://books.google.com/books?id=Mi8MhzheOokC&q=Whirlwind+1951&pg=PA102|title=When Computers Went to Sea: The Digitization of the United States Navy|last=Boslaugh|first=David L.|date=2003-04-16|publisher=John Wiley & Sons|isbn=9780471472209|pages=102|language=en}}</ref><ref name="ProjectWhirlwind" />{{Rp|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. 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 [[Semi-Automatic Ground Environment|ground controlled interception]], and the Whirlwind was the only machine suitable to the task. They took up development under ''Project Claude''.

Whirlwind weighed {{Convert|20000|lb|ST MT}} and occupied over {{Convert|2000|sqft|m2}}.<ref>10 short tons:
*{{Cite web|url=http://ed-thelen.org/comp-hist/BRL-t-z.html#WHIRLWIND-I|title=WHIRLWIND-I|last=Weik|first=Martin H.|date=December 1955|website=ed-thelen.org|series=A Survey of Domestic Electronic Digital Computing Systems}},
20,000 lbs:
*{{Cite web|url=http://ed-thelen.org/comp-hist/BRL2nd/BRL-2ndCompSurv.html|title=WHIRLWIND I|last=Weik|first=Martin H.|date=June 1957|website=ed-thelen.org|series=A Second Survey of Domestic Electronic Digital Computing Systems}}
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