“Harvard Mark I”的意思、由来-开放百科全书

The IBM Automatic Sequence Controlled Calculator (ASCC), called Mark I by Harvard University’s staff,^[1] was a general purpose electromechanical computer that was used in the war effort during the last part of World War II.

One of the first programs to run on the Mark I was initiated on 29 March 1944^[2] by John von Neumann. At that time, von Neumann was working on the Manhattan project, and needed to determine whether implosion was a viable choice to detonate the atomic bomb that would be used a year later. The Mark I also computed and printed mathematical tables, which had been the initial goal of British inventor Charles Babbage for his "analytical engine".

The Mark I was disassembled in 1959, but portions of it are displayed in the Science Center as part of the Harvard Collection of Historical Scientific Instruments. Other sections of the original machine were transferred to IBM and the Smithsonian Institution.

Origins

The original concept was presented to IBM by Howard Aiken in November 1937.^[3] After a feasibility study by IBM engineers, the company chairman Thomas Watson Sr. personally approved the project and its funding in February 1939.

Howard Aiken had started to look for a company to design and build his calculator in early 1937. After two rejections,^[4] he was shown a demonstration set that Charles Babbage’s son had given to Harvard University 70 years earlier. This led him to study Babbage and to add references of the Analytical Engine to his proposal; the resulting machine "brought Babbage’s principles of the Analytical Engine almost to full realization, while adding important new features."^[5]

The ASCC was developed and built by IBM at their Endicott plant and shipped to Harvard in February 1944. It began computations for the U.S. Navy Bureau of Ships in May and was officially presented to the university on August 7, 1944.^[6]

Design and construction

The ASCC was built from switches, relays, rotating shafts, and clutches. It used 765,000 electromechanical components and hundreds of miles of wire, comprising a volume of {{Convert|816|cuft|4=0}} - {{convert|51|ft|m}} in length, {{convert|8|ft|m}} in height, and {{convert|2|ft|m}} deep. It weighed about {{convert|9,445|lb|ST MT|1}}.^[7] The basic calculating units had to be synchronized and powered mechanically, so they were operated by a {{convert|50|ft|m|adj=on}} drive shaft coupled to a {{convert|5|hp|}} electric motor, which served as the main power source and system clock. From the IBM Archives:

The enclosure for the Mark I was designed by futuristic American industrial designer Norman Bel Geddes. Aiken considered the elaborate casing to be a waste of resources, since computing power was in high demand during the war and the funds ($50,000 or more according to Grace Hopper) could have been used to build additional computer equipment.^[9]

Operation

The Mark I had 60 sets of 24 switches for manual data entry and could store 72 numbers, each 23 decimal digits long.^[10] It could do 3 additions or subtractions in a second. A multiplication took 6 seconds, a division took 15.3 seconds, and a logarithm or a trigonometric function took over one minute.{{sfn|Campbell|1999|p=43}}

The Mark I read its instructions from a 24-channel punched paper tape. It executed the current instruction and then read in the next one. A separate tape could contain numbers for input, but the tape formats were not interchangeable. Instructions could not be executed from the storage registers. This separation of data and instructions is known as the Harvard architecture (although the exact nature of this separation that makes a machine Harvard, rather than Von Neumann, has been obscured with the passage of time; see Modified Harvard architecture).

Main sequence mechanism was unidirectional. This meant that complex programs had to be physically lengthy. A program loop was accomplished by loop unrolling or by joining the end of the paper tape containing the program back to the beginning of the tape (literally creating a loop). At first, conditional branching in the Mark I was performed manually. Later modifications in 1946 introduced automatic program branching (by subroutine call).^[10]{{sfn|Campbell|1999|p=53}} The first programmers of the Mark I were computing pioneers Richard Milton Bloch, Robert Campbell, and Grace Hopper.^[11]

Instruction format

The 24 channels of the input tape were divided into three fields of eight channels. Each accumulator, each set of switches, and the registers associated with the input, output, and arithmetic units were assigned a unique identifying index number. These numbers were represented in binary on the control tape. The first field was the binary index of the result of the operation, the second was the source datum for the operation and the third field was a code for the operation to be performed.^[12]

Contribution to the Manhattan project

In 1928 L.J. Comrie was the first to turn IBM “punched-card equipment to scientific use: computation of astronomical tables by the method of finite differences, as envisioned by Babbage 100 years earlier for his Difference Engine”.^[13] Very soon after, IBM started to modify its tabulators to facilitate this kind of computation. One of these tabulators, built in 1931, was The Columbia Difference Tabulator^[14]

“Von Neumann joined the Manhattan Project in 1943, working on the immense number of calculations needed to build the atomic bomb. He showed that the implosion design, which would later be used in the Trinity and Fat Man bombs, was likely faster and more efficient than the gun design.”^[17]

Aiken and IBM

Aiken published a press release announcing the Mark I listing himself as the sole “inventor”. James W. Bryce was the only IBM person mentioned, even though several IBM engineers including Clair Lake and Frank Hamilton had helped to build various elements. IBM chairman Thomas J. Watson was enraged, and only reluctantly attended the dedication ceremony on August 7, 1944.^[18]^[19] Aiken, in turn, decided to build further machines without IBM’s help, and the ASCC came to be generally known as the "Harvard Mark I". IBM went on to build its Selective Sequence Electronic Calculator (SSEC) to both test new technology and provide more publicity for the company's own efforts.^[18]

Successors

The Mark I was followed by the Harvard Mark II (1947 or 1948), Mark III/ADEC (September 1949), and Harvard Mark IV (1952) – all the work of Aiken. The Mark II was an improvement over the Mark I, although it still was based on electromechanical relays. The Mark III used mostly electronic components—vacuum tubes and crystal diodes—but also included mechanical components: rotating magnetic drums for storage, plus relays for transferring data between drums. The Mark IV was all-electronic, replacing the remaining mechanical components with magnetic core memory. The Mark II and Mark III were delivered to the US Navy base at Dahlgren, Virginia. The Mark IV was built for the US Air Force, but it stayed at Harvard.

The Mark I was disassembled in 1959, but portions of it are displayed in the Science Center, as part of the Harvard Collection of Historical Scientific Instruments. Other sections of the original machine were transferred to IBM and to the Smithsonian Institution.^[20]

See also

References

1. ^The machine’s name as actually displayed on the hardware itself is "Aiken-IBM Automatic Sequence Controlled Calculator Mark I". An early photograph (Wilkes 1956:16 figure 1-7) displays the name as "IBM Automatic Sequence Controlled Calculator".
2. ^Bernard Cohen, p.164 (2000)
3. ^Bernard Cohen, p. 53 (2000)
4. ^Bernard Cohen, p.39 (2000) It was first rejected by the Monroe Calculator Company and then by Harvard University.
5. ^{{cite web|url=http://www-03.ibm.com/ibm/history/exhibits/markI/markI_intro2.html |title=IBM’s ASCC introduction 2|accessdate=14 December 2013}}
6. ^{{cite journal|title=Proposed automatic calculating machine (Abstract)|journal=IEEE Spectrum|date=August 1964|volume=1|issue=8|pages=62–69|doi=10.1109/MSPEC.1964.6500770|url=http://ieeexplore.ieee.org/document/6500770/|accessdate=7 August 2017|publisher=IEEE Xplore|issn=0018-9235}}
7. ^{{cite web |title=IBM Archives: Feeds, speeds and specifications ASCC Statistics |url=http://www-03.ibm.com/ibm/history/exhibits/markI/markI_feeds2.html |website=www-03.ibm.com |date=23 January 2003}}
8. ^IBM Archives: FAQ / Products and Services
9. ^Computer Oral History Collection, 1969-1973, 1977Grace Murray Hopper Interview, January 7, 1969, Archives Center, National Museum of American History{{cite web |url=http://invention.smithsonian.org/downloads/fa_cohc_tr_hopp690107.pdf |title=Archived copy |accessdate=2012-10-21 |deadurl=yes |archiveurl=https://web.archive.org/web/20120223191745/http://invention.smithsonian.org/downloads/fa_cohc_tr_hopp690107.pdf |archivedate=2012-02-23 |df= }}
10. ^{{cite book |last1=Beyer |first1=Kurt W. |title=Grace Hopper and the Invention of the Information Age |date=2015 |publisher=BookBaby |isbn=9781483550497 |url=https://books.google.com/books?id=mp5XDQAAQBAJ&lpg=PT78&dq=%22subsidiary%20sequence%20unit%22&pg=PT78#v=onepage&q=%22subsidiary%20sequence%20unit%22&f=false |language=en|pages=78-79}}*{{Cite journal|last=Bloch|first=Richard|date=1984-02-22|title=Oral history interview with Richard M. Bloch|url=http://hdl.handle.net/11299/107123|journal=|language=en-US|volume=|pages=9–10|via=}}*{{Cite web|url=http://www.cbi.umn.edu/hostedpublications/Tomash/index.htm|title=The Erwin Tomash Library on the History of Computing: An Annotated and Illustrated Catalog|last=|first=|date=1948|website=www.cbi.umn.edu|series=CBI Hosted Publications|at=Image: Harvard.Vol 16.1948.subsiderary sequence mechanism, description: H Chapter, pp. 577-578|language=en|nopp=y|archive-url=|archive-date=|dead-url=|access-date=2018-05-08}}*ASCC operational manual, subsidiary sequence control, pp. 22, 50, 57, 73, 91
11. ^Wexelblat, Richard L. (Ed.) (1981). History of Programming Languages, p. 20. New York: Academic Press. {{ISBN|0-12-745040-8}}
12. ^¹{{cite book |author = Maurice Vincent Wilkes |title = Automatic Digital Computers |publisher = John Wiley & Sons |year = 1956 |location = New York |pages = 16–20 |url = https://books.google.com/books?id=n_oNAAAAQAAJ |authorlink = Maurice Wilkes}}
13. ^{{cite web|url=http://www.columbia.edu/cu/computinghistory/comrie.html|title= Columbia University Computing History: L.J. Comrie|accessdate=15 December 2013}}
14. ^{{cite web|url=http://www.columbia.edu/cu/computinghistory/packard.html|title=The Columbia Difference Tabulator - 1931|accessdate=15 December 2013}}
15. ^¹#AIKEN, Bernard Cohen p.166 (2000)
16. ^Bernard Cohen, p. 164 (2000)
17. ^{{cite web|url=http://www.atomicheritage.org/index.php/component/content/262.html?task=view |title=Atomic Heritage Foundation: John von Neumann|accessdate=15 December 2013}}
18. ^¹{{cite book |author= Emerson W. Pugh |title= Building IBM: Shaping an Industry and Its Technology |publisher= MIT Press |year= 1995 |isbn= 978-0-262-16147-3 |url = https://books.google.com/books?id=Bc8BGhSOawgC }}
19. ^{{cite book |author1= Martin Campbell-Kelly |author2 = William Aspray, |title = A History of the Information Machine |publisher = Basic Books |year = 1996 |url = |isbn = 0-465-02989-2 |page=74}}
20. ^{{cite web|title=Collection of Historical Scientific Instruments Mark I|url=http://www.atlasobscura.com/places/mark-i|website=Atlas Obscura|accessdate=2016-05-24}}