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A comment on Germanium transistors: logic circuits in the IBM 1401 computer. Parent comment

Re:Germanium transistors: logic circuits in the IBM 1401 com... by yholio on Wednesday March 03, 2021 @02:54PM (#26333511)
What's DEFL - Diode Emitter Follower Logic, suppose it's IBM's name for ECL? Do we have examples of these circuits being used in critical circuits in mainframes of the 60s?

I can't imagine a logic circuit of that era that was technically capable of being clocked at 100Mhz, 30 years before these frequencies became the norm.

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Re:Germanium transistors: logic circuits in the IBM 1401 com... by kens on Wednesday March 03, 2021 @03:13PM (#26333759)
I've looked, but I can't find anything more about DEFL. (The table says it was used in certain serial numbers of the core memory for the Stretch computer, so it seems rather obscure.)

Based on the speed, it's plausible that it is a type of ECL, but I don't know where the diodes would fit in. IBM had other names such as current-steering logic for ECL.

Keep in mind that the 10ns speed doesn't mean you can run at 100 Mhz, since there are likely to be multiple levels of logic, as well as other delays. But it's still pretty fast.

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Re:Germanium transistors: logic circuits in the IBM 1401 com... by bsder on Wednesday March 03, 2021 @05:08PM (#26335383)
Is it possible this is DTL (Diode Transistor Logic) in IBM-speak?
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Re:Germanium transistors: logic circuits in the IBM 1401 com... by kens on Wednesday March 03, 2021 @05:23PM (#26335609)
It's possible. IBM had several other types of diode-transistor logic including DDTL, SDTRL and CTDL. The emitter follower was more often used with ECL.
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Re:Germanium transistors: logic circuits in the IBM 1401 com... by kens on Wednesday March 03, 2021 @09:06PM (#26337710)
I found an IBM patent for high-speed logic using diodes and an emitter-follower. I don't know if this is "Diode Emitter Follower Logic" but it kind of matches the name.

https://patents.google.com/patent/US3050641A/

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