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Single-chip processors have reached their limits

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Re: Single-chip processors have reached their limits

#131

Post by adwn »

Iwan-Zotow wrote: post #76
AceJohnny2 wrote: post #65

Earlier quoted context omitted.

> But consider also that you can stick chiplets on top of each other vertically. The problem there is heat dissipation. Already the performance constraint on consumer chips like the Apple M1 is how well it can dissipate heat in the product it's placed in (see Macbook Air vs Mac Mini). Stacking the chips just makes it worse.

the problem is signal propagation for light to cross 1 feet should take ca 1ns

Signal propagation latency is only a problem if both end points need to be fully synchronous, which they don't have to be if they're independent units. Even the cores within single-chip multi-core CPUs aren't synchronous to each other, as far as I know.

Re: Single-chip processors have reached their limits

#132

Post by throwawaylinux »

tempnow987 wrote: post #7

"Reached their limits" - I feel like I've heard this many many times before. Not that I doubt it, but just I've also been impressed with the ingenuity that folks come up with in this space.

Microarchitecture performance innovation continues (the M1, Zen3, and Alder Lake cores are all significant improvements over their predecessors), and transistor performance and density continues to increase. We're on the verge of new transistor architecture (FinFET -> GAA) and shrinks and other advancements continue.

Single chip processors have not reached their limits in terms of . For some applications, one piece of silicon is not enough, and that has been true for ever. Early cores were built with multiple chips, later ones had separate cache or FPU add ons, we had (and still have) SMP multi-processors that wire up many chips together, we have discrete GPUs.

So in any given year, with any given silicon technology and logic design, we have virtually always reached the limit of single chip processors, and gone beyond them with multiple chips. And at the same time, the limits of single chip processors have continued to expand year after year.

Both of these things remain true. Relative performance improvements have slowed significantly from where they were 20-30 years ago, but things are still ticking along.

Re: Single-chip processors have reached their limits

#133

Post by AbbeSomething »

chii wrote: post #115
AnthonyMouse wrote: post #99

Earlier quoted context omitted.

Computational complexity and parallelism are orthogonal. Many EXP algorithms are embarrassingly parallel. You still have to do 2^n calculations, but if you have 1000 processors then it will take 1000 times less wall clock time because you're doing 1000 calculations at once. The reason parallelism doesn't "solve" EXP problems is that parallelism grows linearly against something whose time complexity grows exponentiall…

But what if the processor may be made organic, or encoded in DNA, so that replication and protein synthesis is akin to solving the problem? The "computer" grows exponentially, rather than linearly, and so for larger problems, it grows to the size that solves the problem? Or we end up with grey goo...

Are there any examples of reusable "computers" like this? I've seen some demonstrations but they are not generic to the problem and reusable, they seem to have the data encoded in the makeup of the "computer" itself.

I write computers in quotation marks because even if they solve computational problems they are so different from what we are calling computers today, eg: mold growing in a maze and similar.

Re: Single-chip processors have reached their limits

#134

Post by astrange »

gotaquestion wrote: post #87
hinkley wrote: post #55

I hope we are going to get back to a more asymmetric multi-processing arrangement in the near term where we abandon the fiction of a processor or two running the whole show with peripheral systems that have as little smarts as possible and promote them to at least second class citizens. These systems are much more powerful than when these abstractions were laid down, and at this point it feels like the difference bet…

The problem is AMP is very hard to program and debug. In embedded, one core is a scheduler and another is doing some real-time task (like arm BIG.little). In larger automotive heterogeneous compute platform, typically they are all treated as accelerators, or with bespoke Tier-1 integration (or like NVIDIA Xavier). And on top of that, OEMs always want to "reclaim" those spare cycles when the other AMP cores are underu…

M1 is an AMP design, as is every iPhone SoC. It works well although you’ll be surprised if you try to run an SMP workload on every single core.

Re: Single-chip processors have reached their limits

#135

Post by AbbeSomething »

nynx wrote: post #8
retrac wrote: post #6

The best chiplet interconnect may turn out to be no interconnect at all. Wafer scale integration [1] has come up periodically over the years. In short, just make a physically larger integrated circuit, potentially as large as the entire wafer -- like a foot across. As I understand it, there's no particular technical hurdle, and indeed the progress with self-healing and self-testing designs with redundancy to improve…

There are some new chip manufacturing technique coming down the pipeline, which will lead to prices dropping and likely "wafer-scale" will get to the mainstream.

Can you clarify what you mean? How can anything that would use a major share of a wafer or even a whole one be mainstream? Producing a wafer is expensive, the chips are only available to ordinary people in high income markets because you get hundreds or even thousands from a single wafer.

Re: Single-chip processors have reached their limits

#136

Post by tsimionescu »

AnthonyMouse wrote: post #99
tsimionescu wrote: post #98

Earlier quoted context omitted.

Not necessarily. There are problems you can't speed up even if you are given a literal infinity of processors - the problems in EXP for example (well, EXP - NP). Even for NP problems, the number of processors you need for a meaningful speed up grows proportionally to the size of the problem (assuming P!=NP).

Computational complexity and parallelism are orthogonal. Many EXP algorithms are embarrassingly parallel. You still have to do 2^n calculations, but if you have 1000 processors then it will take 1000 times less wall clock time because you're doing 1000 calculations at once. The reason parallelism doesn't "solve" EXP problems is that parallelism grows linearly against something whose time complexity grows exponentiall…

A problem that is not in NP is, by definition, a problem that can't be solved in polynomial time even with an infinity of processors (or equivalently, with speculative execution given a perfect oracle). So, it can't be embarrassingly parallel.

So, a problem in EXP - NP (that is, it can be solved in exponential time, but it can't be solved in polynomial time even if given an infinity of processors) will require exponentially more time to solve for a higher n than a lower n, regardless of how many processors you have - even up to infinity. You may get some kind of speed-up with more processors, but it will not be enough to remove the exponential runtime blow-up.

An example of a problem like this is the Travelling Salesman Problem. As far as is known right now, there isn't even a non-determinstic algorithm that can solve the problem in polynomial time. Even if you had an infinity of processors, and could solve the problem for 1000 cities in 1 minute, you would still need ~2^1000 minutes to solve the problem for 2000 cities. Note: this bound is not proven, there may be some non-deterministic algorithm that can solve it in polynomial time.

I will also note that even for a problem that is in EXP and in NP, so an EXP problem that is embarrassingly parallel, doubling the problem size would require 2^n more processors to keep the same run time, not 2n (assuming it's time complexity is O(2^n)).

Re: Single-chip processors have reached their limits

#137

Post by chii »

AbbeSomething wrote: post #133
chii wrote: post #115

Earlier quoted context omitted.

But what if the processor may be made organic, or encoded in DNA, so that replication and protein synthesis is akin to solving the problem? The "computer" grows exponentially, rather than linearly, and so for larger problems, it grows to the size that solves the problem? Or we end up with grey goo...

Are there any examples of reusable "computers" like this? I've seen some demonstrations but they are not generic to the problem and reusable, they seem to have the data encoded in the makeup of the "computer" itself. I write computers in quotation marks because even if they solve computational problems they are so different from what we are calling computers today, eg: mold growing in a maze and similar.

None that are usable i'm sure - it's merely a theoretical idea.

Re: Single-chip processors have reached their limits

#138

Post by pdimitar »

What we need much more from here on are deterministic processors. There are awesome optimizers out there, including programs with genetic algorithms that find the best way to do a micro task X or Y (part of a much bigger program).

IMO we have a ton of slightly-higher-hanging fruit that we can pick in terms of optimization but the relentless march of the X86 / X64 architecture obstructed that innovation.

Might be time to look inwards and start working more on squeezing the CPUs we have right now for maximum performance.

Re: Single-chip processors have reached their limits

#139

Post by narag »

ksec wrote: post #118
narag wrote: post #103

Earlier quoted context omitted.

Why would 100x something only cost 2x to produce? If you create an app, the cost is mostly developing it. Once you can sell a copy, you can sell 100x for more or less the same cost. It's tricky for physical things. We tend to think that costs correlates with weight or volume, but that's wrong. The price of a typical 100 ml (3.4 fl oz) perfume is around $50 in shops, for an "official" $100 price. The cost of the juice…

That is only in the case of software, where the unit cost does not increase since it is nearly zero. What you wrote about perfume and juice are not unit " cost ", but " price ". Unit Cost, or BOM or COGS does not include --> the perfumist, the bottle, the box, shop markup, distribution markup, marketing, tv commercials, design, samples... I am assuming the "I" here stands for Initial Investment or CapEx. And in the c…

First, I apologize for the confusion, I+D wasn't translated to English: R&D.

What you wrote about perfume and juice are not unit "cost", but "price".

Maybe "cost" has a precise definition in Economics that I'm not aware of, but "price" is definitely not right in this context either. In my example, I can't see how the bottle and the box are not costs.

For me (maybe not correct, but that's what I meant anyway) "cost" is any expense that you incur to put the product in the hands of the final buyer. And cost per unit is total expenses divided by number of units. Feel free to use other words instead of "cost" and "cost per unit" that fit in these definitions.

Let me clarify the original question so it makes more sense. Thirty years ago computers had a single processor. Then they started to make multiprocessor and multicore CPUs. Now it seems that miniaturization is reaching its hard limits so they're wondering how to increase computing power.

One of the logical solutions is to put more processors in the same computer, not in the same chip or waffle (so defect rate is irrelevant here), but more like a "cluster in a box". I guess that would bring a number of problems like heat, but this kind of power doesn't seem the kind you want in your pocket.

So my question was: would this make economic sense? If "cost per unit" is rigid, it wouldn't. If it's driven by market or R&D, it might make sense.

Re: Single-chip processors have reached their limits

#140

Post by RugnirViking »

adhesive_wombat wrote: post #77
candiddevmike wrote: post #23

Earlier quoted context omitted.

Wikipedia link on microlithography if you want a rabbit hole about wafer making: https://wikipedia.org/wiki/Microlithography Being able to print something in nanometers is an overlooked technical achievement for human manufacturing.

If that rabbit hole appeals, the ITRS reports (now called IRDS[2]) are very good mid-level, year-by-year summary of the state of the art in chipmaking, including upcoming challenges and future directions. > Being able to print something in nanometers is an overlooked technical achievement for human manufacturing. IMO, a semiconductor fab probably is the highest human achievement in terms of process engineering. Not o…

is it the same reports accessed by the process in https://irds.ieee.org/home/how-to-download-irds ?
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