In the event of an apocalypse, how long until we could produce CPUs? There are many books on rebuilding a civilization. I think this is too complicated of a q

In the event of an apocalypse, how long until we could produce CPUs? There are many books on rebuilding a civilization. I think this is too complicated of a question to answer in a meaningful way. If by apocalypse you mean a true reset of almost everything and only some humans survived but no information was in tact, probably several thousand years or more likely never. People could draw on cave walls their memories of this civilization. CPU's have a complicated supply chain and there are a myriad of experts that specialize in specific parts of the motherboard, CPU, memory, etc... There is not a single person that has the all inclusive knowledge of engineering a CPU. This assumes we also have people that can refine all the minerals used to craft the parts, the energy requirements to do so and people remain that know how to do this. I assume an apocalypse means we lost many of the people that carry specialized knowledge so most of the R&D would have to be restarted from scratch, again assuming that only some humans survived and all data is gone, power is gone, libraries are gone, etc... This assumes this R&D is the priority of the survivors, which it would not be. Even if all this information was archived on the moon or satellites, nobody would know how to retrieve it and that is assuming any of the survivors even know of it. Current satellites would probably de-orbit in a few generations or sooner. Someone here more knowledgeable could comment on satellites not under active management by people or ground control automation systems. I personally think their priority will just be survival, probably for quite a few generations. If we are being honest with ourselves, many people today would not survive on a scorched and tattered earth. Most would not even survive in the wild without an apocalypse. By the time a sub-set of the survivors pass hunting & gathering great filter, then agrarian and eventually industrial, all the tribal knowledge would have long since aged out. Maybe there could be campfire stories of the SeaPeaYou's, HighScrapers and falling Spams from the SkyNets. I know this sounds negative but I think this is the best case scenario. My personal take-away from this thought exercise is to make the most of computers to augment life improvement and life enjoyment while I can and not depend on them.