Editing IBM System/360 (section)

===Basic hardware components===
[[File:IBM SLT card 03773.agr.jpg|thumb|A single-width [[Solid Logic Technology|SLT card]]. Each square metal can contains a [[hybrid circuit]] with several transistors.]]
[[File:IBM SLT chip, side view.jpg|thumb|upright|Six-transistor solid logic hybrid circuit with cap off]]
[[File:SLT Card Frame.corestore.jpg|thumb|upright|Many SLT cards plugged into an SLT backplane]]

Being uncertain of the reliability and availability of the then new monolithic [[integrated circuit]]s, IBM chose instead to design and manufacture its own custom [[hybrid integrated circuit]]s. These were built on 11&nbsp;mm square [[ceramic]] substrates. [[Resistor]]s were [[screen-printing|silk screened]] on and discrete [[glass]] encapsulated [[transistor]]s and [[diode]]s were added. The substrate was then covered with a metal lid or encapsulated in plastic to create a "[[Solid Logic Technology]]" (SLT) module.

A number of these [https://web.archive.org/web/20050122174353/http://www-03.ibm.com/ibm/history/exhibits/vintage/vintage_4506VV3081.html SLT modules] were then [[flip chip]] mounted onto a small multi-layer [[printed circuit board|printed circuit]] "SLT card". Each card had one or two sockets on one edge that plugged onto pins on one of the computer's "SLT boards" (also referred to as a backplane). This was the reverse of how most other company's cards were mounted, where the cards had pins or [[Edge connector|printed contact areas]] and plugged into sockets on the computer's boards.

Up to twenty SLT boards could be assembled side-by-side (vertically and horizontally, max 4 high by 5 wide) to form a "logic gate". Several gates mounted together constituted a box-shaped "logic frame". The outer gates were generally hinged along one vertical edge so they could be swung open to provide access to the fixed inner gates. The larger machines could have more than one frame bolted together to produce the final unit, such as a multi-frame Central Processing Unit (CPU).