If something happens to TSMC there will be a global effort to lift all that knowledge back into stable, developed countries to continue production as fast as humanly possible.
Just like the lifting of Nazi rocket scientists, it's a technology that is directly intertwined with the existence of contemporary advanced economies/societies, if TSMC ceases to exist there will be a concerted effort from major economies to re-gain that knowledge. Right now it's just too expensive to do it instead of outsourcing it, the moment it becomes an existential threat it won't be relatively that expensive anymore.
I don't think old computers as such will ever be relevant as you envision, if it happens it will be a blip during a gap of 3-5 years until production restarts somewhere else.
The entire Manhattan project ran less than 5 years. If it's top priority for national security (which it absolutely would be), the heavens and the earth can be moved.
Sad to think of the list of things that don't make that cut. You would think that eco-friendly energy independence would merit top "national security" priority.
And food. And yet, pretty much 90% of the world could die in starvation and not a single finger would be lifted. Cut the chips production and it's WW3.
Samsung is probably less than 3 years behind tsmc some complex chips are manufactured in their high end chips, I doubt it will be as catastrophic as we think, most of the critical parts of cars and iot are manufactured in much Biggers litigtaphics than "3n" and Intel produce "7n", the catastrophic part will probably be the political implications of this.
I'm not talking business competition trying to fund R&D into TSMC-levels. It would be national efforts, funded by gobs of state money to set it up and go online as fast as possible.
Later selling to private enterprises, etc. is another matter to be discussed but governments would very very likely be directly involved.
As another comment said, the Manhattan Project took 5 years, it's not impossible.
Just like the lifting of Nazi rocket scientists, it's a technology that is directly intertwined with the existence of contemporary advanced economies/societies, if TSMC ceases to exist there will be a concerted effort from major economies to re-gain that knowledge. Right now it's just too expensive to do it instead of outsourcing it, the moment it becomes an existential threat it won't be relatively that expensive anymore.
I don't think old computers as such will ever be relevant as you envision, if it happens it will be a blip during a gap of 3-5 years until production restarts somewhere else.