IBM Solid Logic Technology Module
A small ceramic circuit module that packed transistors and resistors into a standard unit, used throughout the System/360 family.
Solid Logic Technology, or SLT, was IBM's hybrid circuit design for System/360. A ceramic substrate about half an inch square carried printed resistors and tiny transistor and diode chips, sealed in a metal can. Several modules plugged into a card, and cards plugged into a backplane.
IBM made SLT modules in large volume at its own plants. The approach was a step between wired transistors and monolithic integrated circuits. It made computers smaller, cheaper to build and easier to repair by swapping a card.
Why it matters
SLT let IBM produce a full family of compatible computers from common parts. It also helped the company mass-produce complex logic at a time when integrated circuits were still new.
Key facts
- Used in the IBM System/360 family starting in 1964.
- Each module held discrete transistor and diode chips on a ceramic base.
- Modules mounted on cards that plugged into backplanes.
- Sat between discrete transistors and integrated circuits.
Sources
- Campbell-Kelly, Martin, and William Aspray, et al. Computer: A History of the Information Machine. 3rd ed. Westview Press, 2013.
- Pugh, Emerson W. Building IBM: Shaping an Industry and Its Technology. MIT Press, 1995.
- Computer History Museum online collection catalog (computerhistory.org/collections).