I'm wondering what kind of events or limitations would be needed in a science fiction society hundreds of years into the future in order limit computational advances to the level of the early 70's to late 80's.
Specifically, something that would make people unable to develop better technologies despite trying. So government, religion and other 'soft' limits are not viable.
I'm willing to bend the laws of physics a bit if necessary to make this possible.
You need to kill the microchip, at least when it hits the very large scale integration phase in the 1980's. A couple ways to do this.
For some reason you can't stamp out chips, assembly line style. This could keep them from being super cheap and reliable. If they had to be laid out by hand they wouldn't be cheap and the maximum size would be pretty limited.
Another possibility is that circuits won't work reliably when too close together. So there is a minimum size that is much larger than what we have today (14 nm or so). This will prevent high speed handheld electronics, keeping super computers in the "entire room" size category.
Neither of these things ought to directly impact biochemical processes. Of course eventually there will probably be workarounds, like using organic processing, but you may buy yourself a prolonged period of relative stagnation in the field of electronics.
Shortage of elements used in their CPUs... there are a lot of rare and unusual elements used whioh could run out or be made unavailable, hafnium for example is pretty rare and maybe zirconium ooesnt work out as a suitable replacement. Germanium is somewhat common but not in high concentrations, so maybe mining it becomes difficult due to environmental laws. If you look at other materials maybe you can find more ideas too.
You didn't specify that your a futuristic society was on Earth, so: Lets put your society in a Earth like planet (Light Earth), with an Sun like star to orbit, far away from the galaxy center.
Out stellar system would be in a young star-forming region, so it have less heavy metals available than our current Earth. Our Light Earth may have the same total mass, but most of the metals are inside the planet nucleus, and are hard to find near the surface.
This would slow down advances related to metals, like electricity, computers, and transportation. This way more futuristic technologies would not be possible, or would be really hard to develop.
You asked for a reality-check...
Necessity is the mother of all inventions. Human innovative power is never as strong as when facing hardships. Look through the 100 000 years of human history, and look particularly at all the rough times we have gone through. Through all this humans have continued to develop our understanding of the world, nature, the elements, the laws of nature, and of ourselves. And particularly when pushed — like when at war — humans have shown an amazing ability to improvise, adapt and overcome.
Which means that you are out of luck, because the harder you try to limit progress, the harder humans will try to make progress, and most likely over-compensate in the process.
If you can bend the laws of physics sufficiently, then it might be as easy as adding some property of matter that'll not allow the p-n type of junctions to work. That takes out the compactness of silicon transistors which will make advanced computing devices impossible. No personal computers, no smart phones, no mainframes, no internet and definitely no supercomputers. Vacuum tubes could never be compacted. The new physical property will also potentially have no other repercussions because it affects a completely man made arrangement of materials, so the rest of the world will stay normal.
Alternatively, a more radical approach would be to make silicon (specifically when processed to make circuits) and/or some other critical components required for making ICs radioactive. Now only governments would be able to own computers housed in special facilities.
Alternatively, you can take out the zero based Arabic numerals. If no one invents that way of doing maths, the world will never be able to do advanced maths no matter how hard they try. But this would work only until someone finally stumbles upon it.
You could even change some fundamental property of matter to not allow steam engine to work (for example, let's say that in this universe water/petrol vapors compress to either change state or transfer most of their heat to the container, now no more engines) and there's no industrial revolution, if you can go that far back.
Basically, you select a few inventions/discoveries that were crucial to the new advancements and modify a law of physics to stop it from working.
What about Frank Herbert's solution in Dune? The people of that time had a cultural prohibition on "thinking machines" stemming from an earlier war - the Butlerian Jihad. Not exactly religion, although in Herbert's books it certainly had some religious aspects.
In the original books, it was described as "the crusade against computers, thinking machines, and conscious robots". I always envisioned it just as a revolt against these machines and their users - an oppressed people rising up against their overlords and the tools of their oppression.
In the later books written by Herbert's son, it was expanded into a full-on "Terminator"-type battle against AIs & robots. Opinion is divided on this characterization (and the quality of the later books vs. the original ones written by Frank Herbert). Enough said about that.
In any event, the basic idea is that a traumatic event (major war, disaster, or something) linked to this type of technology could give rise to a social prohibition on their use.
Technically no.
If you have a world which lacks semiconductor materials, you can't make integrated circuits, hence you would be limited to vacuum tube computers.
Vacuum tube computers are the giant room-sized computers that preceded modern day computer, in which the function of integrated circuits falls on large thermionic valves.
Technically, such a computer could do whatever a modern computer can, it's just a matter of processing power. All computers can run all software by definition, so if you made a vacuum tube computer the size of the pentagon, you may be able to play Doom on it, but practically this isn't something which would happen.
It's up to you to decide if this would give the practical limitations you're looking for.
I know you said no religion in the comments, but I think there may be a middle ground worth considering.
What about a society with an extreme value placed on human labor - Protestant work ethic sort of thing. You could relate it to an honor culture, where honor is strictly earned through your labor, and your entire civilization is one big culture of hand craftsmanship.
They could still make some pretty amazing things, even plausibly these early computers. The assembly line is around; it's just fully staffed by humans. But the sort of high-tech tools required to mass produce densely-packed computer processors simply isn't possible.
This way there's nothing that feels like a contrived "oh, god says no computers" and you rely on everyone believing it and not trying. Everyone can strive, with all their might, to advance what they can do. But advanced computers simply aren't on the table, because they don't consider things a skilled human can't produce.
One of the limits in reducing the size of circuits and transistors on a microchip was the inherent radioactivity of the materials composing the microchip itself. Now this level of radioactivity is simply the background radiation. It does allow for computing certainly up to levels more than comparable with current levels.
Assume a world where background radiation levels are significantly higher than those in our world and large-scale integrated solid state circuitry could be effectively impossible.
Since this is part of a science-fiction society hundreds of years in the future, then the increased radioactivity could come numerous sources. The widespread use of nuclear power, nuclear wars, and possibly the necessity to use nuclear pulse propulsion spacecraft, launched from the Earth's surface, for interplanetary travel.
Since space itself is a high-radiation environment the computers used there will be more primitive and more robust than current computers. They could quite easily be the equivalent of 1970s computers. The use of these simpler computers will be more sophisticated and subtle than how computers were used in the actual 1970s. Software engineering will have progressed and programmers will know how to get the most out of 'simple' software applications. Just like they did in the old days, i.e., the 1970s when good programming involved the least number of instructions and clever thinking about how to make it work well and efficiently.
The modern semiconductor industry is critically reliant on a technology known as the Excimer Laser. This is to my understanding the only known laser technology that produces light whose wavelength is shorter than the wavelength that the photoreactive substances used during integration circuit manufacturing react to. without it, manufacturing would require the use of visible light lasers instead, resulting in a limit of feature sizes approximately 10 times large than present, giving us chips of approximate performance of those produced in the early 2000s. This does not get us far enough.
Another critical development is computational lithography. This process relies on a variety of effects of diffraction and polarization that are at best subtle -- it is hard to know what the effect of changing those laws of physics would be on the universe, but they would probably not be immediately apparent.
Thus, by eliminating these 2 advances it would be possible to place a hard limit on semiconductor manufacturing at the shortest viable wavelength of light available for etching masks, which would likely be somewhere around the 400nm range, placing the maximum level of technology as somewhere around 1994: 32-bit computers, megabytes of RAM, low hundreds of megahertz clock rates.
The singularity happened. Runaway AI. Now a godlike being.
It created Planck-scale computronium out of the fabric of space time with minimal disruption of the classic physics we experience. (Computronium is "stuff" optimized to compute stuff).
Physics is seemingly unchanged, except in ways you find fun. Maybe there are FTL gateways, or force fields, or magic. You get to pick.
However, organic life works. Low-information processing computers are as well.
More advanced computers simply do not work.
It has been theorized that the singularity has low level processes policing for a singularity emerging from within its computronium simulation and it is preventing it. Sort of like antibodies.
We are either treated special because we gave birth to it, or because there is no danger of a singularity directly from us.
The wave front of computronium expands out at the speed of light. Within it the various modifications work (for example, the FTL drive system only works within the computronium).
The singularity is a computronium field created by our ancestors. It surrounds us and penetrates us; it binds the reachable universe together.
One solution would be to have a world that has a high level of electromagnetic interference that interferes with the operation of sensitive electrical equipment.
Abnormal solar activity or solar storms can disrupt the functioning of electrical equipment on Earth, but this usually isn't a huge deal because the effect size is modest and because our atmosphere and magnetic field protect us from the worst of this electromagnetic noise. But, on a world with a weaker magnetic field, with a less protective atmosphere, with intense and frequently electrical storms, that is in the process of switching magnetic poles, that is closer to a star (or the same distance from a more luminous star), greater background radiation from heavy radioactive isotypes in the crust of the world, or that is in the vicinity of a star that is less stable than our own, so much shielding would be required to operate sophisticated electrical equipment that it wouldn't be practical to use it except for rare big science experiments that weren't commercially viable comparable in cost and scale to neutrino and dark matter detection experiments and the Large Hadron Collider.
This approach is probably more viable than trying to imagine a world without any viable semiconductors or a world with frequent nuclear detonations causing EMPs.
Another more extreme solution would be to have a highly corrosive atmosphere (a bit like a milder version of Venus) to which biological systems have adapted, that rapidly renders all available metals unusable. In general, a world without semiconductors is hard to imagine, because silicon is so ubiquitous. But, a world that has easily corroded metals (like iron and silver), but not metals that are relatively impervious to corrosion (a bit like the planet in Asimov's Second Foundation that lacks metals and becomes a home to a colony of librarians) is comparatively easy to imagine.
Hostile A.I., smart enough to avoid total defeat, dumb enough to avoid total victory.
Focuses on pillaging and plundering processing resources advanced enough for it to use.
Once it focuses exclusively on a location, it will succeed in invading 99% of the time. And kill the humans since it's there.
This reminds me of a US/Canada TV show called Stargate Atlantis (a spin-off of Stargate SG-1 which in turn is based off the movie Stargate).
In the show, they are in another galaxy populated by several human inhabited worlds. Each world is at a very different stage of development, though most are somewhat primitive. Additionally, there is another race of beings called The Wraith. They are predatory and "feed" on the human population. They are highly advanced with space ships and such.
So, to the question... In this show, many cultures/worlds have existed for several hundreds if not thousands of years. However, when the Wraith "feed" (called a "culling"), they destroy much of the infrastructure and take a good percentage of the population. As a result, no society ever really gets that advanced because they are constantly being brought down by destruction and loss of population.
So, in answer to the question... It seems that something like this may be what you're looking for. Essentially, some mechanism that constantly delays progress so that even after hundreds or thousands of years, the society is still behind the times in terms of technology. Perhaps something that takes the best and brightest (or most of them) every so often, loss of infrastructure, constant rebuilding may be what you're looking for.
Since you didn't mention that technology in general maybe at a 70s level and specifically computer technology, then I would tend to agree with Jason K: you'd have to kill the microchip. However, if it's all technology in general, then something like what I mentioned above would probably be a decent option.
Alastair Reynolds had a setting sort of like this in Terminal World; an unexplained technology exerted a field that prevented non-biologic mechanics below a certain scale to break. It was sort of suggested that some sort of imperceptible vibration was responsible - something biology could handle just fine, but anything with moving parts big enough for humans to have invented can't. He used the field on one planet, with multiple settings to exclude different levels of technology; I think he just wanted to be able to write about nanobots and steampunk in the same book. But you could use something similar, on a massive scale if your civilization needs to be interplanetary.
Of course, it might take some mental gymnastics if you want to have other technology beyond 1970's level; for example, it would be hard to explain 70's computers alongside 21st-century jets.
Make computational advances stay at the level of the eighties. No explanation is needed, really.
At any time the current technology is the best available and upcoming technology has some problems that must be solved before it can become actual technology.
Unless the limitation is important to the story, just have the society not develop microcomputers. It's not important, the fact that microcomputers are not available is established by society not having invented them.
Would you in a modern romance-novel expect a detailed description of why the protagonists aren't using pocket-sized fusion reactors to power their flashlights?
Commersial fusion is a good template, it has been researched heavily but all we really can say about why it isn't viable is essentially we haven't figured it out. A an engineer that has worked with it could list several things that don't work; but couldn't possibly say these several properties of out universe prevents it.
No reason why the same can't apply to computing, they have worked on it for centuries, but haven't figured it out yet.
How about an electro-magnetic pulse?
Our current level of processing power is something of a virtuous circle - in order to have the technology to design and build a chip with thousands of semi-conductors in it, you'll likely need a chip with hundreds of semi-conductors in it.
If an event wiped out the world's integrated circuits, then there's a good chance that the knowledge would remain; but we'd have to start again creating computers with individual transistors again. Computing power probably wouldn't take as long as it did originally to develop, but it should take long enough for a story arc.
I recommend a religion or cult entered around computer technology. They don't actually know how integrated circuits work, so they can't improve on them (hard limit), but the manufacturing process has basically become a ritual. People know how to do it because it was passed down, but they don't understand how it actually works, and they wouldn't deviate from the ritual over time because even small deviations would cause non-functional computer parts.
A society which does not have reasonably advanced computers cannot be "futuristic". Most of the technologies and, by extension, the material elements of civilisation which distinguish the present society from the society of the 1950s cannot exist without computers. Advanced airplane engines are designed and manufactured using computers. Modern cars are manufactured using computers. Most cellular phones, even old-fashioned feature phones, are actually computers. The pervasive communications networks are computer networks. And so on. Without advanced computing there are no digital cameras, no mobile phones, no satellite-based navigation systems, no efficient airplanes enabling low-cost travel, no gigantic ships enabling low-cost transport of stuff from China, no automated factories producing cheap consumer goods.
Historically, when William Shockley invented the transistor in 1947 the future was set. Actually, it was set when they invented crystal radios, which use what we would call today solid-state valves -- the transistor is a simple development. You cannot have transistors but not advanced computers. You must then limit the society to vacuum-tube electronics, or even better, no electronics at all. Maybe in that world Faraday and Maxwell did not exist, so they don't know much about electricity -- but this does not make the society futuristic, it makes it steampunk.
The Lensman series postulated a technology based around vacuum tube tech, only micronized and amplified beyond the point we abandoned them as a viable technology, not to mention...
genetic manipulation by aliens.
Obviously, the details were all handwavium, but at least it gave an intellectual foundation point to rest your suspension of disbelief upon.
Using this concept as a basis, you could postulate that certain inventions were somehow never made and that (for whatever reasons) a different focus in technological advancement became prominent, and said focus has hard-fast limitations on advancement in tech.
However, this still amounts to a soft solution, so I turn to "The Day the Earth Stood Still" (the original black and white movie, or the book it was based off of, NOT the more recent remake). In said movie, as a demonstration of power and proof...
all technology based off of anything electrical or later was selectively turned off, leaving hospitals and other critical facilities running.
If some such similar an effect was postulated to be in effect permanently in the region around your proposed planet/society, that would provide a hard limit, as requested.
An idea: endemic nuclear warfare. EMP would limit usefulness of computers, while physical destruction would prevent construction of progressively better microchip building tools.
Assume that in the near future we have organic computing. Hundreds of years into the future we may lose knowledge of how organic computing came to be. We may end up with computers that are genetically inferior to our earlier models due to infection, inbreeding, or any other organic interference.
Also, we may have powerful AI or computers that are narrowly designed to design other computers. That means we may only need a few specialists to help those systems along. If those specialists go away and those systems degrade, go away, become altered, we may not know how to design or improve computers.
Pay a visit to any semiconductor manufacturer and the answer will slap you right in the face: cleanliness. There's a darn good reason why all the fab workers wear moon suits, and they won't let you anywhere near the shop floor without one. So what if you contrive a situation whereby creating a sufficiently clean environment is impossible? Or the required purity of raw materials is unattainable?
It turns out that these sorts of advances were made circa 1970 to enable building ICs using the NMOS transistor, which has significantly better performance than a similarly sized PMOS transistor, and consumes less power than BJTs. If you are limited to PMOS and BJTs, you can still build reasonably complex ICs, but you will be hamstrung to a roughly 1980s level of technology at best.
In particular, you cannot build CMOS chips without NMOS transistors; though you could build roughly analogous structures using BJTs, they would still be larger and consume considerably more power. But you could still build depletion-load PMOS chips using the same ion-implantation technology as enabled depletion-load NMOS, and that would be important in trying to build 1980s designs.
This would also exclude the larger and more ambitious chip designs of the 1980s from consideration, or at least make them very much more expensive. The 6502 has about 5000 transistors, which should be quite manageable, but the 68000 has as many as 40000, and was thus extremely expensive to produce when first introduced in the late 1970s (with the benefit of NMOS transistors). For comparison the much more capable ARM2 only used 30000, and the 8086 used about 20000.
The 6809, 6309 and 65816 might be representative of more achievable designs. The 6809 was a basic 16-bit CPU using only 9000 transistors. The 6309 extended the 6809 in some logical and useful ways, and probably stayed well under 20000 transistors. Meanwhile the 65816 was designed as an upgrade of the 6502 family with the minimum of additional hardware, and may have stayed under 10000 transistors, though with some significant missing features relative to the 6309.
Larger computers could still be built using SSI and MSI technology, as many of the famous DEC minicomputers were. The principal limitation to these was the sheer cost of installing large memories; this could be worked around to some extent by using disk and tape storage, at a significant performance cost. Their relatively high power consumption and frequent need for repairs would also limit the number of people or organisations which would bother to install one, if even a basic 6502-based microcomputer was widely available.
Based on the availability of the rare earth elements found in microchips, a life form (maybe a thermophyle archaea) degrades circuits under a certain size. The problem is overcome but the protection limits the size to ICs.
I also have to second Frank Herbert's idea of a cultural rejection to thinking machines. It would be no different than our current rejections of GMOs.
have a period where the magnetic poles are switching, you end up with constant emp effects, only hardened electronics will work, which means most electronics are useless and electronics become ridiculously expensive. won't get rid of it entirely but it's not going to be common. downside much higher solar radiation so more skins cancer, greater crop sensitivity, a few bird species go nuts, and few smaller problems.
Unleash a super virus that disables all computers connected to the internet. This could be intentional (terrorism) or accidental. Computers will have to be reinvented, basically, and severely limited in processing power. They will have no networking ability at all, since the super virus is still out there.
