An Interview with Homer Coonce

Early Transistor Digital Logic - Flyable TRADIC to Nike Zeus


Oral History Homer Coonce



I believe the Nike Zeus program also used transistors. What are your recollections of this work?


By the time of the Nike Zeus project, transistor development had made great progress and several types of junction transistors were available. The germanium, diffused junction 2N559 was chosen over other types, including silicon, because at the time we felt comfortable with it. It was one of the first designs available that met our requirements for fan-out, speed, etc., and Western Electric had demonstrated their ability to manufacture them in quantity.


I recall meetings with device designers where various parametric trade-offs were debated. I had developed worst-case equations for the RCTL logic used in Zeus and as different leakage currents and beta combinations were proposed, I would plug the parameters into the equations to be sure we preserved our fan-out requirements. The calculations were made with my "trusty" sliderule. (A laptop would have been nice.)



How were the 2N559 transistor circuit packs deployed into Nike Zeus?


The Nike Zeus circuit pack shown in this Oral History (page 7) was referred to as an "A" module. The system also used a small number of circuit packs which were twice the size of the "A" module. They were referred to as "B" modules.





Oral History Homer Coonce



Both types of modules were mounted on a power and ground distribution plane approximately fifteen inches square. They were interconnected using wire-wrap posts protruding from the top of the module. Power and ground connections were made with wire-wrap posts extending from the bottom of the modules. This larger assembly was called a "C" plane. "C" planes were stacked one on top of the other to form a unit referred to as a "D" unit. As I recall, "C" planes were interconnected using "fuzz buttons". Spring-loaded pins along one edge of the top module made pressure contact with balls of tightly woven wire mesh on the lower module. (They were very similar to the ones used in Flyable TRADIC). Thus, "C" planes could be unstacked for repair or replacement.





Go To Coonce Oral History, Pg 4














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