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Ask HN: How did Apple manage to create such a better chip than Intel?

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Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#41

Post by titzer »

maxioatic wrote: post #29
titzer wrote: post #18

Lots of other comments point out the vertical integration. For raw single-thread performance: 1. ARM64 is a fixed-width instruction set, so their frontend can decode more instructions in parallel. 2. They got one honking monster of an out-of-order execution engine. (630 entries), which feed: 3. 16 execution ports.

I don't fully grasp assembly, instruction sets, and how CPUs work so pardon the silly questions. I think I understand 1) as since they know the width they can more accurately divide the instructions to more parallel executers (whatever they are - the execution ports?) 2) I believe this allows more "pre-work" to get done before it's actually needed, but then the "pre-work" just chills until 3) these things do the work…

For 1), just think of instructions of little bundles of bytes. The CPU runs through the instructions in forward order, jumping around to other bits of the code as it goes. X86 has variable-width instructions (i.e from 1 byte up to 17 bytes--X86 is complex and there are a lot of prefix bytes that have been used to add new functionality over the years). To determine how long an instruction is, you need to decode the bits of the instruction. For ARM64, and most other ISAs nowadays, the instructions are all 4 bytes long. That means they can all be decoded in parallel.

For 2, imagine a boa-constrictor swallowing a huge piece of prey. One mouth (CPU: the frontend) and one rear (CPU: the retirement phase). The instructions go in the front end in the program order. They are decoded into operations that pile up in the middle (the giant bulge in the boa constrictor). When an instruction is ready to go, one of the execution ports (3--think of 16 little stomachs) picks up an instruction and executes it. Then at the backend, the retirement phase, instructions are committed in the order they appeared in the original program, so that the program computes the same result.

By making basically all of the pieces of this boa constrictor bigger and more numerous, it eats a lot more instructions per clock (on average). Making that bulge (the reorder buffer) huge allows the CPU to have high chance of some useful work to feed to one of its 16 stomachs.

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#42

Post by harpratap »

hartator wrote: post #27
oneplane wrote: post #23

It's not just the M1's design, it's what they don't have to do: no need to support anything legacy. You can't change the x86 ISA to the point where it makes a huge difference because it would no longer run x86 code. Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't…

They fully support i386 via Rosetta 2 though. The real explanation is Intel has been complacent and lazy. We had 5 generations of the same chip. Enough is enough.

What about AMD though? They are at par with M1 but use a lot more power while doing so. I don't think it's an Intel problem, it's an x86 problem

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#43

Post by k0stas »

oneplane wrote: post #23

It's not just the M1's design, it's what they don't have to do: no need to support anything legacy. You can't change the x86 ISA to the point where it makes a huge difference because it would no longer run x86 code. Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't…

The overhead of translating x86 instructions to RISC-like microcode is known and is something like 1-2%. This is not the reason for the difference between Intel and Apple.

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#44

Post by the_arun »

oneplane wrote: post #23

It's not just the M1's design, it's what they don't have to do: no need to support anything legacy. You can't change the x86 ISA to the point where it makes a huge difference because it would no longer run x86 code. Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't…

I respectfully disagree. Why can't Intel/AMD make new flavor of chips & motherboards explicitly saying - it doesn't support x86 ISA. Then, wouldn't we address that problem?

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#45

Post by Koiwai »

Several comments mentioned Apple M1 doesn't need to support legacy, but Rosetta 2's support for amd64(yes I choose this term over x86-64) is beyond great, and I looked into that specifically a while ago, some mention Apple had something designed specifically for amd64 emulation, So I'm against that point.

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#46

Post by DaiPlusPlus »

erulabs wrote: post #39
gizmodo59 wrote: post #34

Earlier quoted context omitted.

Can you explain what you mean by Apple's use case vs general purpose chips?

The M1 does one thing: run MacOS and MacOS apps. They can control the vast majority of the compiled code that will be run on the chip - unlike an x86 platform where the exact same architecture is used for desktops, servers and everything in between - including Linux, windows, and Mac. Specifically there is a reference counting optimization on the M1 that dramatically helps performance of compiled Swift apps - somethi…

Could there also be hardware acceleration or built-in support for Objective-C's message-passing? I've always wondered how Apple gets decent performance with Objective-C in-spite of MP given it its complexity compared to vtables (and vtables have the advantage of being easily cachable in L1/L2).

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#47

Post by jcfrei »

This makes me wonder: If there's such a benefit from creating an integrated and specialized chip, will the next consoles follow the same approach? Will they be ARM based? If Microsoft and Sony follow this same model then PC games might be left behind with poorer graphics and fewer titles.

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#48

Post by [deleted] »

the_arun wrote: post #44
oneplane wrote: post #23

It's not just the M1's design, it's what they don't have to do: no need to support anything legacy. You can't change the x86 ISA to the point where it makes a huge difference because it would no longer run x86 code. Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't…

I respectfully disagree. Why can't Intel/AMD make new flavor of chips & motherboards explicitly saying - it doesn't support x86 ISA. Then, wouldn't we address that problem?

[deleted]

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#49

Post by h0l0cube »

oneplane wrote: post #23

It's not just the M1's design, it's what they don't have to do: no need to support anything legacy. You can't change the x86 ISA to the point where it makes a huge difference because it would no longer run x86 code. Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't…

> Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance)n would have to modify all their stuff

This is a crucial point. It's a coordination problem.

Drivers only need to be made for those components that Apple choose for their system vs the multitude combinations of GPU boards, drive systems, motherboard chips, wifi etc etc. that exist for a modern PC.

There's no steering committee for PCs (at least none that could be incorruptible by Intel) that could cause this change to happen industry wide. And there's been little appetite (yet) for Windows/Linux + ARM for consumer PCs to help this happen from the bottom-up.

Re: Ask HN: How did Apple manage to create such a better chip than Intel?

#50

Post by Fazel94 »

ARM is RISC , Intel and AMD are CISC, One important reason is their new pipelining facility.

Apple M1 has 16 units that can pipeline their instructions.

Meaning, they can reorder sequential instructions that aren't dependent on each other to run in parallel. That is not threads or anything, that can be and is being done in a single threaded program.

AMD and Intel have 4 units for reordering tops, because their architecture is CISC and on instruction can be up to 15 bytes. M1 is RISC and instructions are just 4 byte fixed-length. Thus architecturally it is easier to reorder instructions for RISC than CISC.

CISC were better because of the specific instructions but now Apple has stuffed their CPU with specific hardware for alot of things including machine learning, graphic processor and encryption, instead of specific instructions, Apple has specific hardware, and can do with less instructions.

And since they control hardware, software SDKs and OS they can actually get away with such radical changes. Intel and others can't, without a big change in industry.

Source: https://debugger.medium.com/why-is-apples-m1-chip-so-fast-32...

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