In the event of an apocalypse, how long until we could produce CPUs?

The first amplifying vacuum tube was patented in 1908 and you could produce a crude computer from that, even if terribly inefficient.

I imagine civilisation would wind back to around the 18th century, because we would understand things like fertilizers, calculus and how to make steel, but could not immediately use that knowledge to produce steam trains, bicycles or saxophones.

So, assuming an accelerated pace of development thanks to some of this knowledge surviving I'd say 50 years give or take.

You have to define CPUs. Modern CPUs with billions of transistors and nanometer lithography? Or basic processors like a four-function calculator that you can build out of copper wire and relays?

Do you have books with the existing computer engineering literature in them and just no fabs, or do you have to rediscover boolean logic and information theory?

Apocalypse as in complete destruction ? We're fucked, there isn't enough easily accessible fossil fuel for a new industrial revolution, this is our only shot.

It would obviously be possible, since we have CPUs now but once lived in caves.

You can work backwards from "Semiconductor fabrication", which (I guess) would look something like:

Microfabrication > Computation > Manufacturing > Electrical Engineering > Chemical Engineering > Metalworking > Power generation > Basic tools

As to how long this would take, that feels very speculative. Did anyone print a copy of Wikipedia?

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.

I think you need to read the Manga Dr. Stone or watch the anime that is based on it.

Explored on this amazing blog series - https://blog.robertelder.org/how-to-make-a-cpu/

I love this question. A similar question is, assume all knowing oracle, so no research required just execution. How long until we build the CPU?

There's a long and deep infrastructure dependency that needs to exist that would take a long time for all-knowing hunter gatherers to get in place.

It's hard to imagine all advanced semiconductor manufacturing wiped out, worldwide.

But: it's even harder to imagine existing high-tech equipment destroyed, worldwide. A significant % would likely survive. Remember there's like 100B+ cpu's in the world out there.

Starting from there, it would be more like a logistics bottleneck. Like when Covid pandemic hit, or that ship got stuck in the Suez canal. Possibly worse. But manageable.

In short: an event catastrophic enough to nuke that 'installed base', would be extinction-level where "will any humans survive?" would be more relevant than "can we make new cpu's?".

In the event of TSMC's fabs being destroyed by China attacking Taiwan, how long until we could produce modern CPUs?

Not a CPU, but we made a complete and working SAW filter at university. We did everything from design to coating the wafers, lithography to ultimately bonding, housing and testing. I still have the thing somewhere.

Of course we depended on some machines, raw materials and especially a mono crystalline silicon wafer.

I think it is notable, that we did not really depend on an existing computer. Of course a SAW filter is simple, but the 6502 was still made with a similar technique. So if the material science is up to par again a microprocessor is a smaller step than one might think.

Depends on how long roving bands of tribal warlords continued killing each other over previous food and water resources. It might take a minute to get the CPU factories retrofitted to run on diesel generators once a winner emerges and decides to dedicate his fuel stash to manufacturing CPUs.

We already have chips that we're not really able to reproduce, like some of the custom chips and ULA (Uncommitted Logic Array) in older micro computers. The fabs and technology is abandoned, and while we might be able to recreate it the results might not be completely identical chips.

Depends on how severe the apocalypse is. Right now, you could scavenge your way through civilization and not run out of new computers to use / fix, ever. If you were stuck in a cave and had 40 years of your life left, I doubt you'd ever see one. Computers are cool but food takes priority. Not enough hours in a day.

There's a lot we take for granted in civilization. Once those layers are peeled back you're competing for territory with animals and scrounging for survival. Being able to manipulate bits will be extraneous, and really only emerged because of the sheer number of people that are alive right now. With 8Bn people, you get a lot of geniuses.

A better question would be: "how long until you could have a 24/7 source of electricity?"

There's a book called the knowledge. I don't think it gives a specific answer, as it depends how soft the crash and what we have available to recover with. Not only does it take an enormous amount of knowledge to make all the machines that make the gadgets that make the chips, but to even have a society that can make and maintain those machines and the supply chain behind them may well require a large population and to feed that population you might need some petty modern technology.

My guess would be in the hundreds of years from the stone age, assuming we remember those technologies were possible, and we bootstrapped as fast as possible. In practise, you can imagine calamity would breed religious anchors that could weigh us down another thousand years.

Most likely for 0 days, then no one would be able to for decades or centuries, because there will be other much more important priorities. There will be unaffected countries, but they won't do much because supply chain for advanced stuff intertwines the whole world. People would reuse again and again scrap parts and old computers, z80 cpu would outlive everything else. There will be all sorts of flee markets for things like that. I grown up in post soviet crash, I've seen a lot of stuff, local postapocalypse basically, and how people, economy, society adapt and behave in such circumstances.

Depends on how many people die in the apocalypse.

In general, tech requires specialization. (You don't have people who are devoting most of their time to something else who are also producing critical components of our tech tree - the exception being some open-source components.)

Specialization requires enough people that you can put at least one person in each specialty (plus enough to grow food to feed all those specialists).

So you can't create CPUs below a certain population level, whether or not the people remember the scientific knowledge that it all requires.

Asimov’s Foundation tries to answer this by providing a range; if mankind concentrates its effort to document how to bootstrap civilisation, a thousand years. On the other hand, if mankind does not prepare and ignore the inevitable collapse of society, 30.000 years of darkness.

This refers to galactic civilisation. The interesting part is: it depends a lot on how much you pass over, anticipating the downfall.

There is a parallel to deploying software: how good are your instructions, if you can’t be there to fill in the blanks?

Define apocalypse, in the terms of what will remain at the very least. All technology (including discarded old computers) will be unusable? All digital media will be erased? All printed books (specially the IT ones) will be burned down? All the people with present knowledge of those and related technologies will die out, or the time of recovery to think about building back will be too far into the future?

Anyway, can’t stop thinking in the Delorean’s chip of Back to the Future 3.

Ten years

Water wheels for a start, then dams, hydroelectric power and industrial revolution around the corner in just a year. Then ethanol/corn fueled engines and we'll be sailing/flying in no time. Trains will go electric right away instead of steam/diesel/gas. A small country with smart people and good leadership would easily build the first computer and nuclear bomb in less than a decade. From there, world domination.

I had this same thought before Y2K. All the hype around it I wondered if there’s tech stashed away somewhere safe and out of reach from global catastrophes like EMPs or other types of world events. I can guarantee governments have tech stashed somewhere on earth or in space. It’s the most logical way to ensure in an event like that, that those governments can restart and be ahead of everyone else in that event.

Sam Zeloof makes CPUs in his parents garage. If he and his garage survive the apocalypse, he can keep making them ;)

Someone joked that the tribe that protects him will have a major advanage...

I suppose the deeper question is how long until we Factorio our way into being able to prodce all the chemicals and devices involved in the process. I'd love to read an in depth analysis of that question!

Scavanging would outcompete newly made crap CPUs for such a long time, that I would say maybe never?

Making a solid-state transistor would probably be the critical part.

Then we can breadboard one[0].

[0] https://www.youtube.com/watch?v=zNu8yeL3mZs

It seems to me that there are so many layers of “it depends” here that the question isn’t meaningful, at least as originally phrased. OP, can you give us some additional details around your imagined scenario?

Not enough details to answer. But it is interesting to think about exactly how many stacks and layers of knowledge are required for various common day to day things (including cpu).

A related question is if we'd ever be able to reuse existing software.

Is it useful?

We can't. All of the Earth's cheap energy has already been extracted. None of the remaining energy stores can be extracted without modern technology because it would take far more energy to extract than it produces.

If we lose our ability to produce these extraction and refinement tools (or energy becomes too expensive to extract before we have sufficient alternatives), we'll be locked into a subsistence based existence for hundreds of millions of years until the world reserves of coal and oil are slowly replenished.

No energy = no post-industrial goods (and mass starvation due to lack of fertilizer), and definitely no CPUs.