If so, roughly what year electronic could be user by hobbyists?
Would it be better to abandon the existing transistors and etch the gaps or could the old be integrated?
Would it be a green process or would the process be too wasteful for any potential gains from re-using old electronics?
Are you asking if a hobbyist can open up an old cpu and add parts to it to make it faster?
Maybe. It’s been done to a degree, 1971, 4 years ago.
https://www.wired.com/story/22-year-old-builds-chips-parents-garage/
Wasn’t sure how much the hobby evolved since then. I asked hobbyist level as the lowest barrier to entry, but even wondering if something at a lighter scale than Intel could repurpose old CPUs or other ICs.
Unless I’m misunderstanding something, the linked Wired article is about a person designing and making very primitive new chips from scratch, not recycling and modding existing CPUs.
While it is very impressive and surely a great way to learn, its not cost effective at all for what results.