Or more practically, “knowing what is known now, how productive a semiconductor factory could I build for absurdly low budget [$]?” Today 0.8 microns seems slightly less impressive than a really good stone axe, but it took a hell of a lot to get there. I think, given a budget of say, $10 million for the second copy of the factory, it might be possible to get to as low as 0.3 microns with a production of part of a square meter per day. [size of part carefully unspecified, but producing product worth something over 10% of the factory cost per year] What’s possible?

Another variation: due to the terrible aftermath of the flying space bat invasion, humanity is reduced to the technical level of 500A.D. – but some of the survivors come across a former mine shaft filled with the ideal books and equipment needed to restart technology, carefully set aside against this eventuality. So what would you put in that mine?