IBM System/360 Model 20: Difference between revisions

Revision as of 18:19, 14 September 2024

Revision as of 18:22, 14 September 2024

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Developed by IBM in [[Böblingen]], Germany,<ref name=Pugh>{{cite book|last1=Pugh|first1=Emerson W.|last2=Johnson|first2=Lyle R.|last3=Palmer|first3=John H.|title=IBM's 360 and Early 370 Systems|year=1991|publisher=MIT Press|isbn=0-262-16123-0|url=https://archive.org/details/ibms360early370s0000pugh|url-access=registration}}</ref>{{rp|pp.217–218,352}} the system was intended for [[Computer data processing|data processing]] and as a replacement for [[Unit record equipment|tab equipment]]. An incompatible small computer, the [[IBM 1130]] introduced the following year, was designed for scientific and engineering computing.

The design of the Model 20 was the result of a tug of war within IBM. [[John Haanstra]] had wanted a low-end machine that could execute [[IBM 1401]] instructions. [[Fred Brooks]] wanted the machine to have System/360 architecture. The final result was a compromise where cost concerns predominated: the system leased for under $2000 per month ({{inflation|US|2000|1964|fmt=eq}}) including ''[[#IBM 2560 Multi-Function Card Machine|Multi-Function Card Machine]]'' and line printer, compared to around $3000 ({{inflation|US|3000|1964|fmt=eq}}) for a comparable 1401.<ref name=Pugh />{{rp|p.446}}

Based on number of systems sold the Model 20 was the most successful model of System/360. According to Pugh "The number of Model 20 processors installed by the end of 1970 in the United States exceeded 7,400."<ref name=Pugh />{{rp|p.639}} Other models, however, brought in greater revenue. Despite their popularity there are relatively few Model 20s in existence in working condition in 2020.<ref>{{cite web |last1=Bradley |first1=Adam |last2=Blackburn |first2=Christopher |last3=Vaughan |first3=Peter |title=IBM 360 Model 20 Rescue and Restoration |url=https://ibms360.co.uk/ |accessdate=Mar 2, 2020}}</ref>