easist way to build digital logic on civilization collapse?

Question

Assume civilization collapses (to set the stage). What is the easiest way to build digital logic given copious scrap material at-hand? Is there any design I can use to build digital logic at-home? Enough to build _small but useful_ processors? Something like Intell 4004 or the 8086.

ThrowawayR2 · Accepted Answer

Not an EE but I'll proffer an opinion. Pulling chips from scrap is largely useless because there aren't any datasheets available to identify the function, pinout, and timings to operate them. Options that come to mind are:
Diode logic with an amplifier between each stage (https://en.wikipedia.org/wiki/Diode_logic) or DTL. Discrete surface mount diodes are still present on circuit boards and can be extracted for re-use. See the IBM 1401 for an example of a simple DTL computer.
Relay logic (https://en.wikichip.org/wiki/relay_computer). Building relays by hand using scrap material is practical, though difficult. Expect your gizmo to have the size, capability, and power requirements similar to the Zuse Z2 ( https://en.wikipedia.org/wiki/Z2_(computer) ).

ColinWright · Answer

The ARM2 had about 30000 transistors and was already capable of doing significant things. The questions then are:
* How would you build a transistor?
* How would you build thousands of transistors?
* How would you make them reliable?
* How would you power them?
* How would you implement memory?
Depending on what materials you have to hand, and your abilities to machine them, and your power sources, many alternatives present themselves. You could even consider analog computers.