At the time, resistors were cheaper and transistors were still hard to make. This approach was used with the Apollo Guidance Computer, which was built using discrete 3-input RTL-based NOR gates.

Don’t be thrown by its simplicity though. [Andrew] quickly moves on to talk about switching transistors and how they are used to build gates like the OR NOR gate seen above.

Article Open access Published: 25 May 2017 Digital logic circuits in yeast with CRISPR-dCas9 NOR gates Miles W. Gander, Justin D. Vrana, William E. Voje, James M. Carothers & Eric Klavins Nature ...