IBM System/360 Model 40

{{Infobox computing device

| name = IBM System/360 Model 40

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| logo_size = 120px

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| logo = File:IBM Logo 1956 1972.svg

| image = File:IBM System 360 at USDA.jpg

| caption = IBM System/360 Model 40 at the USDA

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| manufacturer = International Business Machines Corporation (IBM)

| family = System/360

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| releasedate = {{Start date|1964|04|07}}

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| discontinued = {{End date|1977|10|07}}

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| memory = 16–128 KB Core

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The IBM System/360 Model 40 was a mid-range member of the IBM System/360 family. It was announced on April 7, 1964, shipped in 1965, and withdrawn on October 7, 1977.{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2040.html|title=IBM Archives: System/360 Model 40|website=IBM|date=23 January 2003|archive-url=https://web.archive.org/web/20231209150627/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2040.html|archive-date=2023-12-09|url-status=dead}}[https://www.flickr.com/photos/dabcanboulet/131523955/ IBM System/360 model 40] (Flickr from Yahoo!)

File:IBM System 360 Model 40 with open gates.jpg

History

On April 7, 1964, IBM announced the IBM System/360, to be available in six models.{{cite book|url=https://books.google.com/books?id=Bc8BGhSOawgC&pg=PA275|title=Building IBM: Shaping an Industry and Its Technology|author=Emerson W. Pugh|year=1995|publisher=MIT Press|page=275|location=Cambridge, Massachusetts|isbn=0-262-16147-8}}{{cite book|title=From Mainframes to Smartphones|author1=Martin Campbell-Kelly|author2=Daniel D. Garcia-Swartz|year=2015|publisher=Harvard University Press|isbn=9780674729063}}Fortune magazine, Sept. 1966, p.118 The 360/40 was first delivered in April 1965.{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|title=IBM Archives: System/360 Dates and characteristics|date=23 January 2003|archive-url=https://web.archive.org/web/20230422131739/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|archive-date=2023-04-22|url-status=dead}}

The 360/30 and the 360/40 were the two largest revenue producing System/360 models,{{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|url=https://archive.org/details/ibms360early370s0000pugh|url-access=registration|date=1991|publisher=MIT Press|location=Cambridge, Massachusetts|isbn=9780262161237}} accounting for over half of the units sold.An ADP Newsletter cited on page 56 in {{cite book|editor-last=Weiss|editor-first=Eric A.|title=Computer Usage Essentials|date=1969|publisher=McGraw-Hill|lccn=71-76142}} shows sales of the 360 Model 30 (36%) and the Model 40 (22.6%), for a total of 58.6%

Models

Five models of the 360/40 were offered.{{cite book|url=http://www.bitsavers.org/pdf/ibm/360/functional_characteristics/A22-6881-2_360-40_funcChar.pdf|title=IBM System/360 Model 40 Functional Characteristics|id=A22-6881-2|date=August 1971}} The D40, E40, F40, G40 and H40 were configured with 16K, 32K, 64K, 128K and 256K of core memory and correspondingly 16, 32, 64, 128 and 128 not a typo: the physical limit seemed to be 224; see p. 17 of the Model 30 Functional Characteristics multiplexer subchannels.

The H40 occupied "more floor space than the other models."{{rp|p.5}}

Configuration

colspan="2" \| A typical, early, basic Model 40 system had the following configuration:{{cite book\|url=http://bitsavers.org/pdf/ibm/360/operatingGuide/C20-1635-2_Model_40_Operating_Techniques.pdf\|title=IBM System/360 Model 40 Operating Techniques\|id=C20-1635-2\|publisher=IBM}}
class="wikitable"
style="vertical-align: top;" \|Model 40 processor	IBM 2040 Central Processing Unit 128 KB byte storage storage protection feature universal instruction set one multiplexor channel two selector channels interval timer
Operator console	IBM 1052 Typewriter- Keyboard (usually assigned to 009 hexadecimal address)
Unit record device	IBM 1442 Card Reader-Punch (00A) or IBM 2540 Reader-Punch (00C & 00D)
Line printer	IBM 1443 Printer (00B) or IBM 1403 Printer (00E)
Disk storage	IBM 2311 Magnetic Disk Drives (190 & 191) or IBM 2314 Direct Access Storage Facility
Tape storage	IBM 2401 Magnetic Tape Units (180 & 181 for 7-track, and 182 & 183 for 9-track)
Telecommunications controller (If used in a telecommunications environment)	IBM 2701 Communication Controller

Microprogramming

Image:IBM 360 20 TROS.jpg (TROS), from the IBM System 360/40]]

Like most System/360 models the Model 40 is microprogrammed. The microcode is stored in transformer read-only storage (TROS), organized as up to 8192 words of 56 bits each. Standard microcode consists of up to 4096 words. The additional 4096 words are used for the 1401 or 1410 compatibility feature.{{cite book |last1=IBM Corporation |title=IBM Field Engineering Manual of Instruction: System/360 model 40 Functional Units |date=1970 |pages=52–73 |url=http://bitsavers.org/pdf/ibm/360/fe/2040/SY22-2843-1_Model_40_Functional_Units_Mar70.pdf}}

IBM 1400 series emulation

With the additional Compatibility Feature hardware and Compatibility Support software under DOS/360, the IBM 1401/1440/1460 object programs can be run in the emulation mode, with little or no reprogramming.{{cite book|url=http://bitsavers.org/pdf/ibm/360/dos/C27-6940-2_14xx_Emulator_Feb69.pdf|title=IBM System/360 Disk Operating System 1401/1440/1460 Emulator Programs: Compatibility Support/30 & /40|id=C27-6940-2|edition=Third|date=February 1969|publisher=IBM}}

Other

Although the cover of IBM's MVT Guide{{cite book|url=http://www.bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC28-6720-5_MVT_Guide_Rel_21.7_Aug74.pdf|title=IBM System/360 Operating System: MVT Guide OS Release 21.7|date=August 1974|publisher=IBM|id=GC28-6720-5}} indicates that even a 360/40 could run MVT,

the IBM operating system used was usually the realistically sized DOS/360,{{Citation needed|date=September 2017}} because all but one model of the 360/40 had less than MVT's minimum memory requirements of 256KB.{{cite book|url=http://www.bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC28-6551-16_Storage_Estimates_R21.7_Apr73.pdf|title=IBM System/360 Operating System: Storage Estimates OS Release 21.7|date=April 1973|publisher=IBM|id=GC28-6551-16}}{{cite web|author=Ray Saunders |url=http://www.os390-mvs.freesurf.fr/mvs360.htm |title=MVS... And Before OS/360 ? |archive-url=https://web.archive.org/web/20071220191855/http://www.os390-mvs.freesurf.fr/mvs360.htm |archive-date=2007-12-20}}

The IBM System/360 Model 40 was developed at IBM Hursley{{cite journal|url=http://www.cs.man.ac.uk/CCS/res/res23.htm|title=Editorial|author=Nicholas Enticknap|journal=Resurrection: The Bulletin of the Computer Conservation Society|issue=23|quote=Mike Flinders, who also worked at Hursley where the 360/40 was designed}} and manufactured at IBM's facilities in Poughkeepsie, New York, Mainz, Germany; and Fujisawa, Japan.{{cite web|url=https://www.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV8001.html|title=IBM Archives: Fujisawa plant|website=IBM|date=23 January 2003|archive-url=https://web.archive.org/web/20230924020615/https://www.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV8001.html|archive-date=2023-09-24|url-status=dead}}

A modified Model 40 ran CP-40, the ancestor of CP/CMS, which in turn was the progenitor of the VM line.

Notes

References

System 360 Model 40