Simply put.

We wouldn't notice anything.

Our perception of the world would be based only on the compute cycles and not on any external time-frame.

The machine could run at a Million Billion hertz or at one clock-cycle per century and your perception of time inside the machine would be the same.

Same with low ram, we would have no indication if we were constantly being paged out to a hard drive and written back to ram as required.

Greg Egan gave a great explanation of this in the opening chapter of his Novel Permutation City

We can see that already when something approaches the speed of light: time slows down for it.

An automatic purge process will start to prevent this. It happened several times in the past. Last time between 2019-2022. It removed circa 7 million processes. With regular purges like this it is made sure that the resources are not maxed out before the admins can add more capacity.

Data in memory will be offloaded to swap space. I doubt we'd notice any fluctuations since we're part of the simulation, but externally it could slow to a crawl and basically be useless. They might shut it down, hopefully just to refactor. But again we probably wouldn't notice any downtime, even if it's permanent.

Maybe we’re already there and death is just the garbage collector freeing up more space.

If our entire universe is a simulation so are our laws of physics, in the parent universe running our simulation the universe might be powered by pure imagination and the concept of memory or CPU cycles or even electricity might not even exist

The OOM killer goes on the prowl.

These answers are all really fun but I didn't see anyone point out one thing: why should we assume that our creators' "computer" architecture is anything remotely similar to our technology? I'm thinking of something like SETI—We can't just assume that all other life is carbon-based (though evidently it's a pretty good criterion). The simulation could be running on some kind of dark matter machine or some other exotic material that we don't even know about.

Personally I don't subscribe to the simulation theory. But if it were true, why would the system have any kind of limitation? I feel like if it can simulate everything from galactic superclusters down to strings vibrating in Planck Time, there are effectively no limits.

Then again, infinity is quite a monster, so what do I know?

Allthat shit you forgot? All that "forgotten" history? There you go.

That's why history repeats itself. It's doing that more frequently these days because there's more people remembering more things.

One word

Alzheimers

Have you ever noticed when you look into a telescope that it takes a little bit to position yourself right to see what you're looking at? And it seems like you used to be able to do it a lot faster? That's not age, that's actually lag time added to cover decompressing the data.

Couldn't they just suspend the simulation until they got more resources? We wouldn't notice a thing.

Render distance would be reduced requiring us to come up with plausible theories to account for the fact that there is a limit to the size of the so-called ‘observable universe’

I did not expect the responses to this question to be as interesting to read as they are 😃

That would only be a problem if you need dynamically allocated memory. It could be a statically allocated simulation where every atom is accounted for.

They take some users offline to free up some memory for everyone else

Limitations of hardware resources show up as "Natural Limits", like the speed of light, in the simulation. The amount of RAM consumed translates to the Hubble Bubble, or the greatest distance light could have traveled since the beginning of our universe, and moreso to the amount of matter and energy contained within it, which is a constant. Energy and matter cannot be created or destroyed, only changed forms allowed, so a set amount from the beginning.

Why would we run out of RAM? Is there new matter being created? It's not like we're storing anything. We will keep using the same resources.

Without knowing the nature of the simulation, we don't even know if there is an analogue for RAM or limited memory. Maybe you could walk in and out a door repeatedly and then glitch into a locked room. Maybe the whole thing would crash - our programs tend to do this when memory runs out. Maybe everything would just get paused or "adjusted down" to fit the restriction. The crash, pause or throttle wouldn't be apparent to us "on the inside" at all if it were happening.

The assumption that it isn't designed around memory constraints isn't reasonable.

We have limits on speed so you can't go too fast leading to pop in.

As you speed up the slower things move so there needs to be less processing in spite of more stuff (kind of like a frame rate drop but with a fixed number of frames produced).

As you get closer to more dense collections of stuff the same thing happens.

And even at the lowest levels, the conversion from a generative function to discrete units to track stateful interactions discards the discrete units if the permanent information about the interaction was erased, indicative of low level optimizations.

The scale is unbelievable, but it's very memory considerate.

@aCosmicWave we all just start moving more slowly.

Fortunately I can report that if anything, we"re having RAM added, because everything keeps speeding up as I get older.

This is a tricky question to answer. To answer this question requires assumptions about how perspectives emerge, if at all, from computation, a theory of time, interpretations of quantum mechanics, and persistence of identity.

Of course, we can start at the simplest possible interpretation, that we live in a "Matrix" style simulation, where we actually have real bodies in the "real world". This sidesteps the question of how to get sentient beings to emerge in a simulation and what that would entail. In this case, running out of RAM would have immediate consequences, since our sense of time in the simulated world would be in 1:1 correspondence with the "real world". We would experience all the possible glitches running out of RAM entails. Imagine taking an Apple Vision Pro and scaling it out. These are your conventional computer glitches. At the point of running out of RAM, you could immediately tell you were in a simulation.

Lets take the next level of interpretation though. Let's assume we live in a "OpenAI Sora" type of simulation. In this simulation, the beings as well as the environment are generated on the fly "randomly". At this point, I am just assuming that subjective perspectives can emerge just as they do in our world, where they are tied to beings that look very much like ourselves. In this case, the subjective time of the simulated beings is entirely uncorrelated with our own time. In a sense, we are just opening a "window" into another universe, like playing back a movie, but the beings themselves would exist whether or not we stumbled upon their particular sequence of bits. The problem of asking what the beings in this type of simulation would experience becomes obvious when you realize that multiple simulators can simulate the exact same simulation with exactly the same sequence of bits. The question then becomes, are the two simulations actually equivalent to each other? From the simulated beings perspective, they could not tell which simulator is simulating them based on their experience, since each simulator can simulate exactly the same bit sequence.

Now this comes to the question of self-locating uncertainty, of being uncertain about which simulator is simulating your own existence. If there were only two simulators in the "real world" simulating your own existence, it would seem to be most reasonable to assign 50% probability that you are being simulated by either simulator. Then the question of what happens when the simulator runs out of RAM turns into the question of which simulator is running out of RAM? If only one simulator runs out of RAM, then from a naive estimate, you would only experience a 50% chance of some sort of "glitch" happening in your world. But of course, we have no way of knowing how many simulators are running this exact sequence of bits. It could very well be infinite. The question then becomes what is the probability distribution over all such simulators running out of RAM? This question seems impossible to answer from the simulated being's point of view.

I haven't even touched upon the question of continuity of identity, of what happens to your perspective when the simulation "crashes" or is paused. This really comes to the question of how conscious awareness supervenes on sequences of bits, or how our perspective gets tied to one sequence of events over another. In other words, this is similar in spirit to the question in the many worlds interpretation of quantum mechanics as to which branch your particular perspective gets tied to when the universe "splits" into different branches. In many worlds quantum mechanics, if there is one branch where the simulator runs out of RAM, there is still the possibility of other branches where your perspective continues unabated. You can see then that this question isn't really a question about simulations or quantum mechanics per se, but of how consciousness decides what perspective comes next.

I suspect the answer is already hidden in the data that we see already. You see, in quantum mechanics there is this notion of "no cloning" where the exact quantum state of a system cannot be cloned, or this would violate the uncertainty principle. I suspect that the solution to the problem of running out of RAM lies in the fact that our own conscious perspective cannot be cloned exactly. In other words, our own conscious experience as we experience it now, might be thought of in the following way. We cannot know what is generating our experience, so we naively assign a probability distribution over all such possible generators of our experience, including those of simulators of our own existence. Some of this probability mass includes situations where our own existence just fluctuates out of the vacuum, but this is vanishingly small. But then there is some other probability mass that is assigned to situations where our existence continues "normally". I suspect the conglomeration of all possible configurations that lead to the particular quantum state that specifies our particular perspective is actually the probability distribution as specified by quantum mechanics. That is, the origin of the probability distribution of quantum mechanics lies entirely in the fact that our own conscious experience can be generated by various possible simulators of various types that converge onto the fixed point probability distribution that is specified by the laws of quantum mechanics.

In this sense, then it is obvious why you cannot clone a quantum state, because a quantum state is a conglomeration of all possible "classical" sequences that have been simulated to such a sufficient degree to be called the same quantum state. In other words, you cannot clone a quantum state because a quantum state is the set of all possible clones that are indistinguishable from each other. Quantum mechanics is the end result of the fact that all possible clones have been carried out on every sequence of bitstrings.

Now the question then arises is why does quantum mechanics seem to obey probability amplitudes and not distributions, that is it utilizes complex numbers instead of ordinary numbers. I suspect this has to do with the fact that quantum mechanics has a certain timeless quality to it, and it is this "time travel" quality that causes the probabilities to be complex valued rather than real valued. You see, if we just assigned classical probabilities to every event, we would just have statistical mechanics instead of quantum mechanics. But statistical mechanics assumes that there is a singular direction of time. I suspect if you relax the notion of a single valued time, you get quantum mechanics.

Thus, simulating a reality, is akin to building a time machine.

Human sacrifice. Dogs and cats living together. Mass hysteria.

Things will stop making sense, people will start to glitch and make horrible decisions that will affect millions, and...

Wait

I imagine it shows itself where processes get dropped, whether it’s walking into a room and forgetting what you were doing, losing train of thought mid sentence, or even passing out when you laid down to watch something.

I know exactly what would happen. It...uhh, what was I gonna say again? It just slipped out, it'll come back...

Have you not played Dwarf Fortress? Frame rate goes way down, a situation imperceptible to the dorfs. Then eventually the operator of the machine looses interest, or a oandemic makes the pop count drop, or a combo of those.

Edit; You should read some Greg Egan if you're into this question.

We go to sleep and it clears

We would probably see more caching of parts of the universe that don't typically observe. Given that our current observation can't see this in current time, we don't immediately notice.

The interesting bit would be to figure out what parts get cached, since we may not be the only sentient life.

This is the entire premise of No Man's Sky.

Who is to say that the sim needs ram. What if it were just a giant state machine where the current state only depends on the previous state. And the entire universe is the “ram”.

I don't necessarily believe this, but I'll play along.

To make it appear natural so we don't notice, death is the first thing that comes to mind. So pandemics, disasters and wars that kill off beings on a large scale to free up memory. A globe with limited surface area seems ideal to stick us on to begin with, with anything outside of that sphere virtually impossible to access. The size of Earth could have been chosen because it fits comfortably within the RAM limits. If Earth is pushing the RAM limits, each planet could be hosted on its own server. So if we someday colonized Mars or the moon, the trip between would be like a server transfer making the RAM issues for interplanetary colonization inconsequential.

If you want to really explore the fringes of this concept, maybe those in the simulation would see glitches that shouldn't happen if it starts running out of RAM. UFOs, shadows, or synchronicities could become commonplace. People could randomly go catatonic or experience amnesia if they're personally impacted. If it got out of control across the entire simulation, perhaps a hard reset would become necessary. It may even be a planned cycle of hard resets based on the anticipated maximum lifespan of the simulation before things start to get fucky due to memory errors. So power on = big bang, and hard reset something like big crunch or heat death of the universe.

I'm more concerned with what happens when the hardware invariably fails...

This is why the Hubble telescope had mirror problems and James Webb was so delayed. The admins had to sneak delays into the simulation while they upgraded the hardware to render more of the universe.