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Comment by cookiengineer | Hacker News Reader

Honestly I don't understand why there's not something like a 256 core ARM laptop with 4TB RAM.

The benefit of ARM is scale of multitasking due to not requiring the same kind of lock states that Intel's architecture requires, and can additionally scale much better than only one physical+virtual core pair.

I guess the only thing that's holding back ARM is Microsoft, as laptops are expected to run an desktop OS that people are comfortable with. Windows RT wasn't really a serious desktop OS and rather a joke made only for some IoT enterprises instead of end-users.

I wish there was more serious hardware than the standard broadcom or MediaTek chips, I'd definitely want some of that...be it as a mini ATX desktop/server format (e.g. as a competitor to Intel NUC or Mac Mini) or as a laptop.

With the ongoing energy crisis something like solar powered servers would be so much more feasible than with x86 hardware.

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> Honestly I don't understand why there's not something like a 256 core ARM laptop

The high power ARM cores aren’t that small. If you took the M2 and scaled it up to 256 cores, it would be almost 7 square inches. You can’t just scale a chip like that, though, so the interconnects would consume a huge amount of space as well. It would also consume over 1000W.

The latest ARM chips are great, but some times I think the perception has shifted too far past the reality.

7 square inches would also include an enormous GPU and tons of accessories.

The actual cores are about .6/2.3 mm², and local interconnects and L2 roughly double that.

So with just those parts, 256 P-cores would be about 1.5 square inches, and 256 E-cores would be about half a square inch. And in practical terms you can fabricate a die that's a bit more than a square inch.

Of course it wouldn't use 1000 watts. When you light up that many cores at once you use them at lower power. And I doubt a 256 core design would have all that many P cores either.

As a rough estimate, you could take the 120mm² M1 chip, add 28 more P-cores with 110mm², 220 more E-cores with 300mm², 128 more MB of L3 cache with 60mm², 100mm² of miscellaneous interconnects, and still be on par with a high end GPU.

That sounds doable but is pushing it. A 128 core die, though, has nothing stopping it except market fit.

even a 128 core part made like that will perform pretty atrociously. scaling up the core count without scaling the cache count means you have a lot of cores waiting for memory. also when you have 128 cores, you almost certainly need more memory channels to have enough bandwidth.

I explicitly included more cache.

And the memory controllers aren't that big on the die. You could include a bunch more on a 128 core model.

Could we make the chips go slower like around 1Ghz? Maybe that is not feasible with the current software architecture to achieve great user experience.

> The benefit of ARM is scale of multitasking due to not requiring the same kind of lock states that Intel's architecture requires

I have no idea what you mean by this. The only x86 feature I can think of that might qualify as a 'lock state' is a bus lock that happens when an atomic read-modify-write operation is split over two cache lines. That has a very simple solution ('don't do that'--you have no reason to), and anyway, one can imagine more efficient implementation strategies

> can additionally scale much better than only one physical+virtual core pair

I have no idea what you mean by this either. Wider hyperthreading? It can be worthwhile for some workloads (and e.g. some ibm cpus have 4-way hyperthreading), but is not a panacea; there are tradeoffs involved.

I'd guess they're referring to ordinary reads/writes having acquire/release semantics on x86 and relaxed on ARM.

The largest number of high-performance ARM cores you can get in a single socket is the Ampere Altra Max with 128 ARM Neoverse-N1 cores. At 2.6 GHz the processor consumes 190 W, and at 3.0 GHz up to 250 W. This is a server chip, not something you can put in a laptop.

Source: https://www.anandtech.com/show/16979/the-ampere-altra-max-re...

I think because general compute is hard to parallelize, so 256 cores doesn't help much in practice. (Compute that does parallelize well already runs on GPU).

I get that hugely parallel applications already run on the gpu, but wouldn't something like 4 power and 28 efficiency cores kinda make sense?

Not as much as say, 4 power cores, 4 efficiency cores, and 24 gpu cores.

>I guess the only thing that's holding back ARM is Microsoft

It's not Microsoft holding it back. It's Qualcomm.

Apart from their very latest SOC (designed by a bunch of ex-Apple employees, no less) their CPUs have are significantly worse than x86 in terms of general performance and have persistently lagged 4 years behind Apple in terms of performance (3 years behind x86). They sell for the same price per unit as x86 CPUs do, so there aren't very many OEMs that take them up on the offer given the added expense of having to design a completely different mainboard for a particular chassis.

As such, x86 is the only game in town if you're buying a non-Apple machine; Qualcomm's products aren't cheaper and perform much worse outside of having more batter life. Sure, Qualcomm owns Nuvia now, but that acquisition will still take some time to bear fruit.

> that acquisition will still take some time to bear fruit.

It might be a very long time considering Arm is suing to get Qualcomm to destroy Nuvia's work.

Really looking forward to buying a 256-core laptop and seeing almost all tasks using 1 single core.

Let's get real here, most things can't be parallelised at all. We must strive for better single core performance.

Let's get real. Most times you're not doing a single task on your laptop.

These days I only see a single core loaded up to 100% when I grep through a big directory or when I encounter a bug in some software.

Most of the time, it's either all cores are equally idling or equally doing something heavy (like building a big project).

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