Things you can do with diodes

> The reason I put “gate” in scare quotes in the illustration is that the circuits are not readily composable to implement more complex digital logic...

Any good suggestions on resources talking about building complex digital logic out of something more suitable?

They might be referring to RTL (resistor-transistor logic). A transistor in the circuit can maintain the same output current that was input. (A transistor in fact a diode and a half.) RTL was superseded by TTL (transistor-transistor logic) but, hey, the Apollo computers that put astronauts on the Moon used RTL logic.

You could start with the late Don Lancster's book [1].

I have a little "breadboard helper" that I am wrapping up (that includes a project manual) for creating RTL circuits and others [2]. (I hope to sell a few.)

RTL book [1]: https://archive.org/details/RTL_Resistor-Transistor_Logic_Co...

Prototyping [2]: https://cdn.bsky.app/img/feed_fullsize/plain/did:plc:oxjqlam...

https://en.wikipedia.org/wiki/Logic_family has a list of common families; of particular note is CMOS, which is essentially what modern computing is based on.

Bebop To The Boolean Boogie might be useful for you - it's kind of a kids book but the concepts are all well done.

While diodes alone are not suitable for complex logic, they were instrumental on making computers cheaper in the late vacuum tube era. Vacuum tubes have fairly low reliability and short usable life so having too many of them in your computer is really bad for the cost and reliability of your system. Early transistors were not much better. They would get better over time, but cheap, reliable mass produced diodes were available long before transistors got there.

And while diodes alone cannot do it, a system with a few vacuum tubes to provide the gain and driving a whole lot of diodes made a lot of computers possible at price points that vacuum tubes alone could only dream of. An example is the hacker folklore sweetheart LGP-30, of The Story of Mel fame. 113 vacuum tubes driving 1500 diodes made for a computer that was the size of a fridge, weighed 800 pounds, drew 1.5kW and cost $50k (~500k in modern money), which made it pretty much a personal computer for the late 50's.