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Comment by wtallis | Hacker News Reader

> "But I always assumed whiz-bang mathematicians had already figured out, I dunno, the threshold at which a processor can be nanosized, or like how big a processor could become before the distances became too great that due to the speed of light further computational advancement wasn't possible."

We're nowhere near the absolute limits imposed by the fundamentals of thermodynamics, quantum mechanics, etc. Those are relatively straightforward bounds to calculate but are completely useless for anything but extremely long-term projections.

What we wish we could compute is what the limits are on current manufacturing techniques and incremental advances from that. But we don't know precisely how many incremental improvements we have left to discover before we need to abandon silicon entirely.

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I was doing some back of the envelope math for a blog post last night[1] and it looks like we're not that far away from the limits of what's possible - at least for non-reversible computing. Getting rid of a bit of information as in a Nand get is always going to cost at least 2.75 zeptoJoules and current transistor technology can do it for an attoJoule, so just another factor of 360 to go. Of course then we can try to transition to reversible computing to get around that[2].

[1]http://hopefullyintersting.blogspot.com/2017/04/the-coming-i...

[2]https://en.wikipedia.org/wiki/Reversible_computing

If I recall correctly, the lower bound on energy for destroying a bit depends (linearly?) on the temperature. Couldn't performance then be improved by cooling?

Yes, you're correct and I probably should have mentioned that.

I don't think it will matter much though. Whether you have to remove input power as heat or expend power to cool likely won't make a whole lot of difference. Just that the delta-t will be a lot larger and so it may actually cost more to keep that ultra-cool machine ultra-cool.

Maybe future data-centers will be used to pre-heat the water that goes into the turbines that power the electricity plant, in some kind of perverse version of a perpetuum mobile.

You'd need to make up for the difference lost on each cycle with extra fuel.

Or we could put future datacenters in space behind sunshades and get them really cold by default.

Bandwidth might leave something to be desired.

You need really big radiators for that. In space, waste heat is a huge problem.

Where did you get the number for attojoule per gate operation?

A factor of 360 is closer than I would have guessed. But that's still at least 8 doublings of compute efficiency. We've never had concrete roadmaps that far out—that would be like scheduling the introduction of FinFETs while Pentium 2s were first hitting the shelves. Nobody's ever been able to predict that far in advance which fabrication technologies will end up being economical at scale and required at which node. (Just look at how well the industry has coped with having to put off EUV so many times.) With the looming end of silicon scaling, those thermodynamic limits certainly don't look any less out of reach.

But we don't know precisely how many incremental improvements we have left to discover before we need to abandon silicon entirely.

Well, it is not as if we will just suddenly stop using CMOS, but the end of improvements is in sight:

https://en.wikipedia.org/wiki/5_nanometer

If we are willing to putter along with no process improvements whatsoever, then yes, we can keep using 5nm indefinitely. And no doubt there will be incremental improvements in performance and yield at that node.

But we can't, and won't stop there to continue to drive down the cost of computing. It is just the end of the road for CMOS lithography.

What are your thoughts on the drivers for reducing the cost of computing beyond CMOS?

> But we can't, and won't stop there to continue to drive down the cost of computing. It is just the end of the road for CMOS lithography.

I mean, is there any reason to believe this is actually true? There's no law that just because something is super useful its price will continue to drop forever. Just check out this chart: https://www.nrdc.org/sites/default/files/import/switchboard/.... The blue line is the inflation-adjusted price of electricity by year. I think it's fair to say that electricity is even more vital to the modern economy than compute power, and that having more of it for cheaper would unquestionably raise the standard of living for everyone. There's also a functional and mostly-free market for its production. And yet its real cost has remained essentially stagnant over the last 40+ years.

Now, there are obviously reasons why Moore's law has been a thing for so long (probably a lot to do with the exponentially increasing number of chips we use and the experience curve http://www.economist.com/node/14298944), but the last 50 years in chips may have been more the exception than the rule.

I mean, is there any reason to believe this is actually true? There's no law that just because something is super useful its price will continue to drop forever.

The entire computer industry, well, the entire technology industry is founded on compute power becoming cheaper each year.

What happens to these billion-dollar companies when that is no longer the case? Will Intel's investors be OK with it when they announce that they won't be coming out with anything much better than what they've currently got? Or will they be punished (severely) in the stock market after such an announcement? [1]

The board of directors will respond to pressure from the investors (or get replaced), and will replace company leadership if needed to continue advancement in technology.

And so they (or someone else) will invest in new technologies to move beyond CMOS lithography, such as molecular nanotechnology. Which will disrupt everything else related to technology and biology as well.

[1] I read articles about gamers buying 5-year old Xeon processors for their game machines for $70 USD which are competitive with current-generation i7 desktop processors that cost much more. If Intel can't sell new processors that are effectively better than older ones, that's going to be a real problem for them, and the stock market will eventually notice.

> The entire computer industry, well, the entire technology industry is founded on compute power becoming cheaper each year.

No, we've just gotten used to it. So now, like any junkie with a bad habit we're going to have to get used to doing without that. Or deal with the increased electricity bill.

> The board of directors will respond to pressure from the investors (or get replaced), and will replace company leadership if needed to continue advancement in technology.

Company leadership being replaced is not going to magically change the laws of nature.

At some point even Intel investors will have to accept that there are such things as physical laws and nature doesn't care one bit about your quarterly earnings reports.

Company leadership being replaced is not going to magically change the laws of nature.

Well, that's just it, we haven't hit the physical limits of computing yet. But we are indeed close to the limits of what is practical with CMOS photo-lithography.

At some point even Intel investors will have to accept that there are such things as physical laws and nature doesn't care one bit about your quarterly earnings reports.

This acceptance process will be quite painful, and someone, some way, some how will step in to promise greater returns.

CMOS process scaling has been a pretty amazing unicorn. The fact that neither Intel nor anyone else has unveiled a CMOS 2.0 isn't for lack of research. There are various possibilities but they're either tactical and limited or very much still in the Labs phase.

I agree that the consequences of compute power no longer advancing year-to-year will be significant but I can't agree this is a case of nobody's trying hard enough.

I agree that the consequences of compute power no longer advancing year-to-year will be significant but I can't agree this is a case of nobody's trying hard enough.

I look at these yuuuuge teams at Intel working on their processors, and what kind of returns are we getting on that investment? How much are they, in comparison, investing in molecular nanotechnology related research?

I look at this, and it is mostly software-ish things:

http://www.intel.com/content/www/us/en/education/highered/re...

There is some hardware stuff, further down the page, and some talk of the post-CMOS world. But I don't see enough. In my view, they're not placing nearly enough emphasis on the foundational technologies they need for their business.

Not being privy to the details of Intel's R&D budget I don't really have an opinion on how their dollars are allocated. I will say that development tends to benefit from large teams more than speculative future research. I'm sure a very large proportion of their R&D budget goes to where revenue is going to come from over the next few years.

It's also the case that Intel has become less forthcoming on their semiconductor research directions so I wouldn't necessarily expect there to be a lot of information on their website.

>Abandon silicon entirely

Abandon for what? In many series they hand-wave this away using words like "hyperspace substrate" or "dark matter" or "unobtanium." Do we have an idea of what we could use in reality?

I'm just curious, people. I knownothing about this.

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