Standard Modular System
Encyclopedia
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. They were used throughout IBM's second generation computers, peripherals, the 7000 series
, the 1400 series
, and the 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 SMS was superseded by Solid Logic Technology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's mounted on them.
SMS cards were constructed of individual discrete components mounted on single sided paper-epoxy printed circuit board
s. Single width cards were 2.5 inches wide by 4.5 inches tall by 0.056 inches thick, with a 16 pin gold
plated edge connector
. Double width cards were 5.375 inches wide by 4.5 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 buss 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 Customer Engineer 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 Customer Engineer 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).
When SMS was originally developed, IBM anticipated a set of a couple hundred standard card types would be all that would be needed, making design, manufacture and servicing simpler. Unfortunately that proved far too optimistic as the number of different SMS card types soon grew to well over 2500. Part of the reason for the growth was that multiple digital
logic families were implemented (ECL, RTL, DTL, etc.) as well as analog circuits, to meet the requirements of the many different systems the cards were used in.
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
ized circuit boards and mounting racks developed by IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
in the late 1950s, originally for the IBM 7030 Stretch. They were used throughout IBM's second generation computers, peripherals, the 7000 series
IBM 700/7000 series
The IBM 700/7000 series was a series of large-scale computer systems made by IBM through the 1950s and early 1960s. The series included several different, incompatible processor architectures. The 700s used vacuum tube logic and were made obsolete by the introduction of the transistorized 7000s...
, the 1400 series
IBM 1400 series
The IBM 1400 series were second generation mid-range business decimal computers that IBM sold in the early 1960s. They could be operated as an independent system, in conjunction with IBM punched card equipment, or as auxiliary equipment to other computer systems.1400-series machines stored...
, and the 1620
IBM 1620
The IBM 1620 was announced by IBM on October 21, 1959, and marketed as an inexpensive "scientific computer". After a total production of about two thousand machines, it was withdrawn on November 19, 1970...
. SMS was superseded by Solid Logic Technology
Solid Logic Technology
Solid Logic Technology was IBM's method for packaging electronic circuitry introduced in 1964 with the IBM System/360 series and related machines. IBM chose to design custom hybrid circuits using discrete, flip chip-mounted, glass-encapsulated transistors and diodes, with silk screened resistors...
(SLT) introduced with System/360
System/360
The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...
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's mounted on them.
SMS cards were constructed of individual discrete components mounted on single sided paper-epoxy printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s. Single width cards were 2.5 inches wide by 4.5 inches tall by 0.056 inches thick, with a 16 pin gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
plated edge connector
Edge connector
An edge connector is the portion of a printed circuit board consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a single discrete female connector , and they also tend to be...
. Double width cards were 5.375 inches wide by 4.5 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
Wire wrap
Wire wrap is a technology used to assemble electronics. It is a method to construct circuit boards without having to make a printed circuit board. Wires can be wrapped by hand or by machine, and can be hand-modified afterwards. It was popular for large-scale manufacturing in the 60s and early 70s,...
pins. All interconnections were made with wire-wrapped connections, except for power buss 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 Customer Engineer 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 Customer Engineer 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).
When SMS was originally developed, IBM anticipated a set of a couple hundred standard card types would be all that would be needed, making design, manufacture and servicing simpler. Unfortunately that proved far too optimistic as the number of different SMS card types soon grew to well over 2500. Part of the reason for the growth was that multiple digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
logic families were implemented (ECL, RTL, DTL, etc.) as well as analog circuits, to meet the requirements of the many different systems the cards were used in.