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Single-chip processors have reached their limits

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Re: Single-chip processors have reached their limits

#71

Post by tonyarkles »

narag wrote: post #66

I hope somebody with relevant knowledge can answer this question, please: what % of the costs is "physical cost per unit" and what % is maintaining the I+D, factories, channels...? In other words, if a chip with 100x size (100x gates, etc.) made sense, would it cost 100x to produce or just 10x or just 2x? Edit: providing there wouldn't be additional design costs, just stacking current tech.

It's been a while since I've been out of that industry, but back around the 45nm days, one of the biggest concerns was yield. If you've got 100x the surface area, the probability of there being a manufacturing defect that wrecks the chip goes up. Now, you could probably get away with selectively disabling defective cores, but the chiplet idea seems, to me, like it would give you a lot more flexibility. As an example, let's say a chiplet i9 requires 8x flawless chips, and a chiplet Celeron requires 4 chips, but they're allowed to have defects in the cache because the Celeron is sold with a smaller cache anyway.

In the "huge chip" case, you need the whole 8x area to be flawless, otherwise the chip gets binned as a Celeron. If the chiplet case, any single chip with a flaw can go into the Celeron bin, and 8 flawless ones can be assembled into a flawless CPU, and any defect ones go into the re-use bin. And if you end up with a flawed chip that can't be used at the smallest bin size, you're only tossing 1/4 or 1/8 of a CPU in the trash.

Re: Single-chip processors have reached their limits

#72

Post by macrolocal »

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.

For example, there's lots to explore in the VLIW space.

Re: Single-chip processors have reached their limits

#73

Post by alain94040 »

throwaway4good wrote: post #26

"Single-Chip Processors Have Reached Their Limits Announcements from XYZ and ABC prove that chiplets are the future, but interconnects remain a battleground" This could easily have been written 10 years ago, and I bet someone will write it in 10 years again. We need these really big chips with their big powerful cores because the nature the computing we do only changes very slowly towards being distributed and parall…

Correct. Also known as Rent's rule. According to Wikipedia, it first was mentioned in the 1960s: https://en.wikipedia.org/wiki/Rent%27s_rule

Re: Single-chip processors have reached their limits

#74

Post by wmf »

narag wrote: post #66

I hope somebody with relevant knowledge can answer this question, please: what % of the costs is "physical cost per unit" and what % is maintaining the I+D, factories, channels...? In other words, if a chip with 100x size (100x gates, etc.) made sense, would it cost 100x to produce or just 10x or just 2x? Edit: providing there wouldn't be additional design costs, just stacking current tech.

The way TSMC amortizes those fixed costs is to charge by the wafer, so if your chip is 100x larger it costs at least 100x more. (You will have losses due to defects and around the edges of the wafer.) You can play with a calculator like https://caly-technologies.com/die-yield-calculator/ to get a feel for the numbers.

Re: Single-chip processors have reached their limits

#75

Post by Iwan-Zotow »

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…

speed of light ~ 1*10^9 feet/sec

To cross one foot - no less than 10^-9 sec = 1ns

Re: Single-chip processors have reached their limits

#76

Post by Iwan-Zotow »

AceJohnny2 wrote: post #65
galaxyLogic wrote: post #57

Earlier quoted context omitted.

Sounds like a great development if it works out. But consider also that you can stick chiplets on top of each other vertically. That means you can put chiplets much closer together than if they were constrained to exist on the same single plane of the wafer. Now how about stacking wafers on top of wafers? That could be super, but there might be technical difficulties, which maybe sooner or later can be overcome.

> 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

Re: Single-chip processors have reached their limits

#77

Post by adhesive_wombat »

candiddevmike wrote: post #23
AceJohnny2 wrote: post #14

Earlier quoted context omitted.

To clarify and contextualize a bit what you're saying: The one big obstacle in creating larger chips is defects. There's just a statistical chance of there being a defect on any given surface area of the wafer, defect which generally breaks the chip that occupies that area of the wafer. So historically, the approach was to make more smaller chips and trash those chips on the wafer affected by defects. Then came the "…

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 only do you "print" nanometric devices, you do it continuously, in a multi-month pipelined system and sell the results for as little as under a penny (micros, and even the biggest baddest CPUs are "only" a thousand pounds, far less than any other item with literally a billion functional designed features on it).

[1]: https://en.wikipedia.org/wiki/International_Technology_Roadm...

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

Re: Single-chip processors have reached their limits

#78

Post by 2OEH8eoCRo0 »

wmf wrote: post #47
2OEH8eoCRo0 wrote: post #16

Earlier quoted context omitted.

> The M1 Ultra is fabricated as a single chip. I'm curious how much the M1 Ultra costs. It's such a massive single piece of glass I'd guess it's $1,200+. If that's the case it doesn't make sense to compare the M1 Ultra to $500 CPUs from Intel and AMD.

I estimate that Apple's internal "price" for the M1 Ultra is around $2,000. Since most of the chip is GPU, it should really be compared to a combo like 5950X + 6800 XT or 12900K + 3080.

It wouldn't surprise me. M1 Ultra has 114 billion transistors and a total area of ~860 square mm. For comparison, an RTX 3090 has 28 billion transistors and a total area of 628 square mm.

Re: Single-chip processors have reached their limits

#79

Post by 2OEH8eoCRo0 »

grishka wrote: post #46
2OEH8eoCRo0 wrote: post #16

Earlier quoted context omitted.

> The M1 Ultra is fabricated as a single chip. I'm curious how much the M1 Ultra costs. It's such a massive single piece of glass I'd guess it's $1,200+. If that's the case it doesn't make sense to compare the M1 Ultra to $500 CPUs from Intel and AMD.

If there's a defective M1 Ultra, they can cut it in half and say those are two low-end M1 Max.

Wouldn't they only get, at most, one low-end M1 Max if there is a defect?

Re: Single-chip processors have reached their limits

#80

Post by 2OEH8eoCRo0 »

mrtksn wrote: post #21
2OEH8eoCRo0 wrote: post #16

Earlier quoted context omitted.

> The M1 Ultra is fabricated as a single chip. I'm curious how much the M1 Ultra costs. It's such a massive single piece of glass I'd guess it's $1,200+. If that's the case it doesn't make sense to compare the M1 Ultra to $500 CPUs from Intel and AMD.

Wouldn't the price be primarily based on capital investment and not so much on the unit itself? After all, it's essentially a print out on a crystal using reeeeeally expensive printers. AFAIK Apple's relationship with TSMC is more than a customer relationship.

In a parallel universe where Intel builds and sells this CPU- what's the price? Single chip, die size of 860 square mm, 114 billion transistors, on package memory.

It just got me thinking the other day since all of these benchmarks pit it against $500-$1000 CPUs and it doesn't seem to fall in that price range at all. Look at this thing:

https://cdn.wccftech.com/wp-content/uploads/2022/03/2022-03-...

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