Ask HN: In the event of an apocalypse, how long until we could produce CPUs?
Would it even be possible at that point?
68 comments
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 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?"
That’s fragile even now…
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.
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.
Wind is readily available… easy to harvest and renewable. So is water now that we understand energy storage and transport via electricity were at most 100 years from restarting modern civilization.
You can't build and maintain those technologies without a ready supply of energy, and more importantly energy storage and distribution (which is MUCH more expensive and complicated for renewables).
And we don't have that yet. Every step of getting renewable energy from its source to the place where it performs work still depends so heavily on fossil fuels that we simply won't be able to survive without it for many decades to come (perhaps even centuries).
Losing our ability to extract fossil fuels at scale within the next 50 years would basically spell our doom.
And we don't have that yet. Every step of getting renewable energy from its source to the place where it performs work still depends so heavily on fossil fuels that we simply won't be able to survive without it for many decades to come (perhaps even centuries).
Losing our ability to extract fossil fuels at scale within the next 50 years would basically spell our doom.
I think you need to read the Manga Dr. Stone or watch the anime that is based on it.
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?
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?
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.
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.
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).
Explored on this amazing blog series - https://blog.robertelder.org/how-to-make-a-cpu/
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.
In the event of TSMC's fabs being destroyed by China attacking Taiwan, how long until we could produce modern CPUs?
Intel still fabs their own CPUs. They're behind, but by what, a year or two?
Sure we would fall behind in some stuff, especially AI, but does it really matter if suddenly all we have is 2-5 year old CPU technology? Mostly everything should work as good as it does today. We will just need a bit more power.
They'll actually be destroyed by US missiles launched from Philippines to prevent factories falling into Chinese hands. But yeah, there's a high change that they go poof and with them 3/4 of the world's productive capacity for modern chips.
There are plenty of CPUs to mine - not all are recycled. Why produce them at all?
As long as it takes ASML to ship the lithography machines to the US or Germany?
There's a lot more that goes into building CPUs than lithography machines. A lot of it also hard to replicate across spaces and may not even be possible to note. That's why Intel's strategy for making new manufacturing facilities is called "Copy Exactly" (https://en.wikipedia.org/wiki/Copy_Exactly!)
Even if you have a mandate to build baby build, TSMC Arizona looks like they are taking around 3 years from groundbreaking in 2021 to being operational in 2024/2025 (src for groundbreaking: https://www.tsmc.com/static/abouttsmcaz/index.htm. src for operational: googled it). You could make an argument that some of this was delays due to government regulations around how the funds are spent, americans are slow to build etc etc. Cutting it in half is still ~1.5 years.
Even if you have a mandate to build baby build, TSMC Arizona looks like they are taking around 3 years from groundbreaking in 2021 to being operational in 2024/2025 (src for groundbreaking: https://www.tsmc.com/static/abouttsmcaz/index.htm. src for operational: googled it). You could make an argument that some of this was delays due to government regulations around how the funds are spent, americans are slow to build etc etc. Cutting it in half is still ~1.5 years.
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?
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?
It's not the same. Now a lot of raw materials are hard to reach and deep down in the ground, since the we took all the easy stuff already.
But they are already out and processed you just need to obtain them and maybe recycle
> Did anyone print a copy of Wikipedia?
Yes, https://en.wikipedia.org/wiki/Print_Wikipedia
Yes, https://en.wikipedia.org/wiki/Print_Wikipedia
„The bound paper volumes, each running 700 pages, represented a fraction of the 7,473 total volumes necessary to render the encyclopedia's extant text on that date.“
So, there are some missing volumes. And they don't print the pictures.
So, there are some missing volumes. And they don't print the pictures.
It would be interesting if we could tag wiki articles as 'vital' or some such for these reasons. Then one could filter by this and save/print. Or maybe a 1-10 scale.
Of course, there'd be disagreement over which things got said designation, so some criteria would have to be established up front.
Of course, there'd be disagreement over which things got said designation, so some criteria would have to be established up front.
> It would obviously be possible, since we have CPUs now but once lived in caves.
That's a big assumption. The modern world was built in easily accessible fossil fuels. We've used basically all of the easily accessible oil and a lot of the easily accessible coal.
Without an easily accessible surplus it's hard to go from agriculture to modern society.
That's a big assumption. The modern world was built in easily accessible fossil fuels. We've used basically all of the easily accessible oil and a lot of the easily accessible coal.
Without an easily accessible surplus it's hard to go from agriculture to modern society.
We also dug out millions of tons of useful materials out of ground, purified them and concentrated them in cities and along roads etc. We cleared forests on most of continents to let people do farming there.
In Eastern Europe at least the biggest limit on farming and state-building in early middle ages was clearing the forest for farming. It was the biggest energy expanditure for people there, and it took hundreds of years to get to a state in which most of the land is available for agriculture. If the apocalypse was quickly over - we'd get to continue from that point without spending all that energy again. If it takes 50 years or more - most of Europe would be one huge forest again.
Depending on the kind of apocalypse all you'd need to do might just be to scavange for usable solar panels/wind turbines/car batteries and starting agriculture in the places that are still available.
Or you'd need to start from scratch, but then we're talking centuries.
In Eastern Europe at least the biggest limit on farming and state-building in early middle ages was clearing the forest for farming. It was the biggest energy expanditure for people there, and it took hundreds of years to get to a state in which most of the land is available for agriculture. If the apocalypse was quickly over - we'd get to continue from that point without spending all that energy again. If it takes 50 years or more - most of Europe would be one huge forest again.
Depending on the kind of apocalypse all you'd need to do might just be to scavange for usable solar panels/wind turbines/car batteries and starting agriculture in the places that are still available.
Or you'd need to start from scratch, but then we're talking centuries.
I'm curious on how easy would be to with solar with the knowledge we have now in material science
Impossible, you wouldn't have any of what's needed to build a solar panel. No rare earth, no plastics, &c. they're all byproducts of the virtually free fossil fuel we had at the begging of the industrial revolution. You could find oil oozing out of the ground in some places
A "solar panel" does not have to be a photovoltaic panel. A much simpler panel can heat water to use in a steam turbine.
We probably wouldn't even be able to source iron ore at that stage, let alone process it to make any kind of useful turbine, but let's say you make a working steam turbine from wood and clay, a DIY solar powered steam turbine is quite a few steps before modern CPU
Depending on your location, there are places where you can't not find iron. Recycle! Civilization might be lost but all that processed and purified iron didn't disappear, it's just hiding under some dirt.
There is so much scrap iron. The quality might not be the best but it’s easy to get with time and hand tools
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.
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.
I also read the book. As far as I remember, it will be a relatively big problem to manage fields, to operate - for example - the „three-field system“* and to exploit the harvest properly.
* https://en.m.wikipedia.org/wiki/Three-field_system
* https://en.m.wikipedia.org/wiki/Three-field_system
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.
I had my large box of older microelectronics wrapped in some layers of aluminum foil to make a fun postapo party thingy. Still have it wrapped. There's hundreds of CPUs there, few full PC computers, hard drives and CDs with Windows XP, Linux and DOS, and a lot of microcontrollers + related components.
Don't scavenge raid me please, I am open to trade.
Don't scavenge raid me please, I am open to trade.
That's a very optimistic outlook after it was revealed what preparations had been taken to deal with a global pandemic, a risk scenario that at least every country had a playbook for.
I just think it is not possible to meaningfully prepare for a once-in-a-century event. You simply cannot sustain significant budgets for such scenarios.
I just think it is not possible to meaningfully prepare for a once-in-a-century event. You simply cannot sustain significant budgets for such scenarios.
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?
Is it useful?
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.
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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.
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.
A related question is if we'd ever be able to reuse existing software.
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.
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.
Also in the event of an apocalypse - the first generation could have all the awareness of technology, knowledge etc but the people who are experts may die out? Even if experts exist the transfering of what to build into "how" to build may need a lot of nurturing - Eg a chip-design expert knows it all - but may not be an expert in building a fab (not even considering the resources needed) to build this chip. But in the world where survival is paramount chip-design is just now a luxury skill and very few incentives exist to urgently preserver/pass down this knowledge? My guess is if apocalypse doesnt turn into anarchy and a rort, you need stability and peace during which technological experimentation/building to florish. SO yeah 50-100 years seems reasonable.
Personally I don't believe in an utter apocalypse like in some zombie movie. There are too many solar panels and car batteries scattered around the globe for them to be all destroyed.
Just the base transceiver stations, which commonly have backup power, would be enough to maintain some degree of civilisation.
Just the base transceiver stations, which commonly have backup power, would be enough to maintain some degree of civilisation.
One hurdle is that the easy to mine materials have already been mined. We have been using progressively more sophisticated methods of ore finding, mining and purification.
Doing that the second time around would be harder. Though we can probably recover good quality materials from scraps.
Doing that the second time around would be harder. Though we can probably recover good quality materials from scraps.
Exactly, second time round it's going to be a civilisation built on recycling. It's crazy to think that by going slightly backwards the whole way forward would be so different.
Early civilisation was hunter-gatherers, scavenging for food and resources. Imagine a new civilisation where we scavenge the remnants of where we're are now. The progress forward would be very quick, but also so very different.
Early civilisation was hunter-gatherers, scavenging for food and resources. Imagine a new civilisation where we scavenge the remnants of where we're are now. The progress forward would be very quick, but also so very different.
During the Christian dark ages, the occupants of Constantinople lived within walls they did not have the knowledge or skill to engineer and build. I imagine that a post-apocalyptic society may feel the same.
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.
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.
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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.
There is enough fuel if we are smart about it. Grow trees, process into woodgas, reuse old infrastructure. Add other kinds of biogas into the mix. Use old hydro ponds and rivers too. Geothermal where it's available. Wind generators are trivial to build. Solar thermal energy can give a lot for relatively minimal engineering effort.
And then some time after the apocalypse - nuclear energy. If the knowledge is preserved and security/regulatory standards lowered, the engineering itself is not too complicated. It's likely that some of the old nuclear reactors would survive the apocalypse.
And then some time after the apocalypse - nuclear energy. If the knowledge is preserved and security/regulatory standards lowered, the engineering itself is not too complicated. It's likely that some of the old nuclear reactors would survive the apocalypse.
The path from wind powered generators to an Intel 4004 is long, especially without plastics, which we would never develop and for which all alternatives are still, with today's technology, very limited
Realistically we probably wouldn't even need cpus and would have much more important things to work on, good luck smelting iron with biogas...
Nuclear power plants need constant maintenance, France had to shut down a good parts of their reactors during covid because they couldn't work on them due to covid restrictions, and that's very far from an apocalypse, let the rot 100 years and they'll be unusable
Doing what we did without virtually unlimited free energy is like sending a kid to climb the everest, naked, before you taught him how to walk. Petrol is the backbone of everything, medicine, agriculture, metallurgy, &c. We haven't found alternatives for a lot of use cases and that's with out current tech, a reboot would be game over
Realistically we probably wouldn't even need cpus and would have much more important things to work on, good luck smelting iron with biogas...
Nuclear power plants need constant maintenance, France had to shut down a good parts of their reactors during covid because they couldn't work on them due to covid restrictions, and that's very far from an apocalypse, let the rot 100 years and they'll be unusable
Doing what we did without virtually unlimited free energy is like sending a kid to climb the everest, naked, before you taught him how to walk. Petrol is the backbone of everything, medicine, agriculture, metallurgy, &c. We haven't found alternatives for a lot of use cases and that's with out current tech, a reboot would be game over
Powder River Basin, Wyoming. There's a few billion tons of coal there, and it's close enough to the surface that you could reach it with hand tools.
I mean, it's not near anything else, but it's there...
I mean, it's not near anything else, but it's there...
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!
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!
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.
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?
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?
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.
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.
To expand a bit more, energy is the fuel of civilization, since we won't have oil at surface level and solar won't be possible without panels, we should concentrate in generating hydroelectric power from rivers that will still be there. With unlimited power everything else is just as easy to rebuild.
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.
Anyway, can’t stop thinking in the Delorean’s chip of Back to the Future 3.
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?".
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?".
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
Then we can breadboard one[0].
[0] https://www.youtube.com/watch?v=zNu8yeL3mZs
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.
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.