Comment by atq2119 | Hacker News Reader

Comment by atq2119 | Hacker News Reader

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This is what happens when a huge proportion of your die isn't doing instruction decoding.

That's a misconception. Yes, decoding x86 is somewhat more complicated, as far as I'm aware that's mostly because instruction length differs at a byte granularity. Still, the area dedicated to it simply isn't that large on those huge out of order designs.

I'm sure the instruction encoding plays some role, but I suspect what we're seeing is rather down to consistently good micro-architecture execution over the years and Apple being ahead of everybody else on manufacturing process.

Compared to the x86 processors that exist today, M1 also benefits from having the memory in-package.

Intel tried to be brave with Itanium, but failed because compilers weren't up to the job at the time.

Compilers "failed" because VLIW is fundamentally not a particularly useful idea. The main problem for general purpose single-thread performance is memory latency, and VLIW just doesn't help there.

> Compilers "failed" because VLIW is fundamentally not a particularly useful idea.

I think the problem isn’t just that it’s not particularly useful, but that it’s an actively bad idea. It statically encodes ILP that we get dynamically in chip designs today, which means that ILP can no longer react to changing conditions, like literally any core architecture changes as the underlying hardware evolves (or even on the same die, say finding itself running on an efficiency core rather than a performance core or vice versa) or running in an SMT environment in which it is not the only instruction stream going through the pipeline.

Adapting to advancing hardware isn't impossible. It's been awhile since I've looked so details are a little hazy, but I know the Mill architecture had an answer to this. I believe they were using effectively two-pass compilation. The first compiled against an abstract version of the architecture, and this is what was distributed. Then this could be further specialized on the user's machine as at that point the limits of the hardware would be known.

I don't recall if they had an idea for SMT as well or not. It's possible they wrote it off entirely, particularly after Spectre and all that.

You are correct that with a lot of effort you can get a compiler to emit VLIW instructions that can claw back some of these problems and have some, but not all, of the information you have available to the processor core at runtime which can make things slightly smarter. And with all of that effort which involves changing software distribution models, jettisoning energy efficient flexible heterogenous architectures, and abandoning SMT, you might be able to get something close to performing as well as… what we already have today without VLIW.

Not sure why anyone thinks that’s an argument for doing it.

> Not sure why anyone thinks that’s an argument for doing it.

Because it didn't take very much effort and it doesn't require changing distribution models or abandoning those things.

Not disputing what you're saying on instruction decoding but there is a lot of other stuff on an x86 processor that Apple hasn't needed or chosen to implement: 32bit, AVX, legacy SIMD, legacy modes, Intel Management Engine plus probably a more complex instruction set. Individually these may not make a difference but add them all up ....

> Individually these may not make a difference but add them all up ....

... and it still may not make a difference.

I have AVX512 on my laptop. Is it used by any software I use? No. Does it take up a lot of die area? Definitely.

Doesn't Apple use TSMC manufacturing?

Yes, and they are the only ones on TSMC 5nm currently.

That's because apple bought the entire 5nm production capacity/runs for basically for the entire last quarter of 2020.

I can tell you some companies were not too pleased about that.

Ah yeah, Apple has f-you money and it knows how to use it.

They did this with FedEx planes out of China years back, forget which iPhone version, but they basically did the same thing they booked everything. All FedEx planes only had iPhones and everybody complained. I don't think they have tried that stunt again.

Is there anything preventing those companies from "ganging" up on Apple and buying capacity jointly? Are they too many and too small? Is it possible to share wafer-space with other companies or does having multiple designs add too much complexity/cost?

I think Apple essentially outbid them, which it was able to do because it is has both large volume and large profit margins.

Which companies?

AMD.

Intel failed because AMD exists and has a cross license agreement that allowed them to be clever.

Without AMD in the picture, Itanium issues would have eventually been sorted out.

There would have been no Intel on IBM compatible PCs without x86 cross licensing, so you could make the point that AMD allowed Intel to thrive.

What? I was there on the early days, that just makes no sense.

Cyrix, VIA and friends were ocean drops, hardly available outside US.

Very unlikely that IBM would have used the 8088 without a second source - so literally Intel needed firms like AMD.

Not unlikely, it was a condition.

Nope, it was a condition from government to buy PCs from IBM, most of their computers have always been single source.

So what were the second source from all major IBM computers throughout its history?

Sorry, don't know what point you're making here.

"However, IBM required that Intel find a second-source supplier because production had to be guaranteed and it was too risky to rely on a single company as the sole source of its chips."

https://jolt.law.harvard.edu/digest/intel-and-the-x86-archit...

That was a first for IBM, and althought not mentioned there I seem to recall it had something to do with selling PC to the goverment as well.

I seem to recall that IBM had second source rights to the 8088 too which presumably made the choice easier.

Fair enough, then I am most likely wrong here.

I have to say I'm confused now!

Feeling a bit nostaligic now as my first job was with IBM selling the original PC to small businesses. Not the hardest job!

Well, yes, if Intel had no competition at all they might have been able to force whatever garbage on the market.

I actually liked Itanium and don't see it as garbage, and see as an unfortunate turn of events that I am not running one on this laptop.

Also don't get the point of the cheering for AMD, because apparently many don't get that without Intel licenses, which depend on Intel existence, AMD won't have much to play with anyway.

20 or so years later, it is my impression that there are no compilers that can do enough ILP (on software not specifically written for the Itanium) to justify the Itanium’s VLIW.

Intel licensed some stuff to Cyrix, VIA, AMD, Harris and possibly others at the time. But if AMD didn’t license AMD64 back (by way of cross licensing) things might have been grim for Intel back in 2003-2008 when AMD was killing it previously.

Intel did nothing out of the goodness of their heart, and neither did AMD - so I’m not sure why it is bothering you that people are cheering for AMD for providing (at this point) a technically and economically better product, and hating on Intel for being a fat cat. The pendulum may swing back sooner or later, both technically/economically and public opinion wise.

I don't know much about Itaniumm, but that was a server architecture, right? That target platform would made it difficult to achieve the same performance per watt as the mobile focused ARM chips.

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