Standard Modular System: Difference between revisions

Revision as of 06:50, 22 April 2015

Revision as of 05:16, 11 January 2016

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{{Refimprove|date=May 2010}}

{{Other uses|IBM SMS (disambiguation){{!}}IBM SMS}}

[[File:SMScard.jpg|thumb|A single -width SMS card.]]

[[File:IBM 1401 card cage.agr.jpg|thumb|SMS card in an [[IBM 1401]] mid-size computer.]]

[[File:SMS card from IBM 1401.agr.JPG|thumb|SMS card from a 1401]]

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The '''Standard Modular System (SMS)''' was a system of standard [[transistor]]ized circuit boards and mounting racks developed by [[IBM]] in the late 1950s, originally for the [[IBM 7030 Stretch]].<ref>{{cite web|url=http://www.computer-museum.ru/books/archiv/ibm36040.pdf#page=18|title=The 360 Revolution|last=Boyer|first=Chuck |date=April 2004|publisher=IBM|pages=18|accessdate=25 November 2013}}</ref> They were used throughout IBM's second generation computers, peripherals, the [[IBM 700/7000 series|7000 series]], the [[IBM 1400 series|1400 series]], and the [[IBM 1620|1620]]. SMS was superseded by [[Solid Logic Technology]] (SLT) introduced with [[System/360]] in 1964, however they remained in use with legacy systems through the 1970s.

Many IBM peripheral devices that were part of System/360, but were adapted from second-generation designs, continued to use SMS circuitry instead of the newer SLT. These included the 240x-series tape drives and controllers, the 2540 card reader/punch and 1403N1 printer, and the 2821 Integrated Control Unit for the 1403 and 2540. A few SMS cards used in System/360 peripheral devices even had SLT-type hybrid IC'sICs mounted on them.

SMS cards were constructed of individual [[discrete component]]s mounted on single -sided paper-epoxy [[printed circuit board]]s. Single -width cards were 2.5&nbsp;inches wide by 4.5&nbsp;inches tall by 0.056&nbsp;inches thick, with a 16 pin [[gold]] plated [[edge connector]]. Double width cards were 5.375&nbsp;inches wide by 4.5&nbsp;inches tall, with two 16 pin gold plated edge connectors. Contacts were labeled ''A–R'' (skipping ''I'' and ''O'') on the first edge connector, and ''S–Z, 1–8'' on the second.

The cards were plugged into a card-cage back-plane and edge connector contacts connected to [[wire wrap]] pins. All interconnections were made with wire-wrapped connections, except for power bus lines. The back-plane wire-wrap connections were mostly made at the factory with automated equipment, but the wire-wrap technology facilitated field-installation of engineering changes by customer engineers.

Some card types could be customized via a "program cap" (a double rail metal jumper bar with 15 connections) that could be cut to change the circuit configuration. Card types with a "program cap" came with it precut for the standard configuration and if a Customercustomer Engineerengineer needed a different configuration in the field he could make additional cuts as needed. This feature was intended to reduce the number of different card types a Customercustomer Engineerengineer had to carry with him to the customer's site.

The card type was a two to four letter code imbossed on the card (e.g., ''MX, ALQ''). If the card had a "program cap" the code was split into a two letter card type code and a two letter "cap connection" code (e.g., ''AK ZZ'').