Standard Modular System: Difference between revisions

Revision as of 00:23, 18 March 2018

Revision as of 00:27, 18 March 2018

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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 [[IBM 2400|240x-series tape drives]] and controllers, the [[IBM 2540|2540 card reader/punch]] and [[IBM 1403|1403N1 printer]], and the [[IBM 2821 Control Unit|2821 Integrated Control Unit]] for the 1403 and 2540. A few SMS cards used in System/360 peripheral devices even had SLT-type hybrid ICs 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 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 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 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 embossed 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'').