Sam Zeloof’s project is the exact one I had in mind when writing my comment. His work is extremely impressive, but it’s almost shameful that for over 40 years (collective) we as hobbyists have not had the ability to manufacture even something as simple as a 4004. May Sam’s work progress, and may we all build on his success.
> I've thought about this, more in the context of post-apocalyptic computing rather than trust, FWIW.
Post-apocalyptic computing is one possible motivation to look at this, but other reduced-tech settings like a fully independent Mars colony also simply cannot function without a way to fab simple IC logic. That, or we’re happy to go back to early Apollo era tech levels.
RE: computers from scratch in the absence of IC fabrication. I think our best chance is vacuum tubes. Mechanical relay computers seem to have been phased out in favour of vacuum tube solutions pretty quickly, so I guess there must have been some compelling reasons to do so (my guess - speed and failure rate of individual switching components). Couple that with old-school electromechanical tech for IO/industrial sequencing, several K of delay line/core/Williams Tube memory, and you’re golden.