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Undocumented arm64 ISA extension present on the Apple M1

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Re: Undocumented arm64 ISA extension present on the Apple M1

#61

Post by rgovostes »

mhh__ wrote: post #51
rgovostes wrote: post #25

Earlier quoted context omitted.

On the other hand, Apple released their 64-bit ARM backend for LLVM[1] in 2014. They announced their intention do so almost immediately after the first ARM64 phone, but the process took several months because it had to be merged with a duplicate backend developed by others. I think it is likely that support for these instructions will be upstreamed to LLVM, and the teams involved in this monumental transition (which…

My point about the docs isn't the day-to-day stuff, but the things that cannot be machine generated - to write a good compiler you need to know the details of how the CPU is put together underneath. Intel will give you 800 pages on how to optimize for their current ISA (AMD will give you 45, but still)

As I understand it, Intel will also sell you a compiler that can optimize better than GCC because they know internal microarchitecture details. To me, that seems like a more clear-cut by-design conflict of interest between chip designer and user than these undocumented instructions.

Re: Undocumented arm64 ISA extension present on the Apple M1

#62

Post by tenebrisalietum »

user-the-name wrote: post #48
tenebrisalietum wrote: post #17

Earlier quoted context omitted.

Apple can make tools that use the undocumented ISA, which they don't have to release to the public, potentially using it to develop applications with performance advantages that no one other than Apple can attain. It's similar to how Microsoft doesn't make all APIs on Windows public and uses non-public ones for various reasons--except this is in hardware. It's possible the undocumented ISA is used to speed up x86 emu…

> Apple can make tools that use the undocumented ISA, which they don't have to release to the public, potentially using it to develop applications with performance advantages that no one other than Apple can attain. Why would they? They sell hardware, not really software.

Hardware doesn't work without at least some sort of software.

I really wish they (or any one with modern fast CPU and motherboard designs) would sell hardware only bare-bones with no OS or even bootloader, but history shows a mass market won't support that.

Re: Undocumented arm64 ISA extension present on the Apple M1

#63

Post by ithkuil »

Teongot wrote: post #26
hyperpallium2 wrote: post #23

After four different CPU ISA's (68000, powerpc, x86, ARM) an Apple ISA is next.

There's a tidy mathematical progression in Apple CPU architectures. 6502 (Apple 1,2,3): 1976 68k (Mac): 1984 (+8 years) PPC: 1994 (+10 years) x86: 2006 (+12 years) ARM: 2020 (+14 years) If the trend continues, we will see Apple's next architecture in 2036.

2036, Apple Mill

Re: Undocumented arm64 ISA extension present on the Apple M1

#64

Post by 2wrist »

vegetablepotpie wrote: post #8
lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

Apple added custom instructions on top of the ARM instruction set to do matrix operations. Matrix operations are used a lot in some algorithms, such as in computer graphics and machine learning and these instructions help those operations go faster. Although the ARM ISA has a multiply and accumulate instruction, it would take many more instructions on a standard ARM core to compute a matrix with only standard instruc…

Similar to Altivec from the PowerPC days?

Re: Undocumented arm64 ISA extension present on the Apple M1

#65

Post by EricE »

mhh__ wrote: post #7
lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

In the bigger picture Apple aren't really documenting anything for their new toys, which is not the end of the world but is a huge step back for openness. There is - as far as I can see - no long-form documentation for M1 other than patents. I already refuse to own apple products so I don't really have any skin in the game, but consider that if microsoft were like this the blind eye would not be turned - buy our new…

Or maybe different people have different needs and don’t care if every device is “open”.

The vast majority of people are not enamored with technology for technologies sake. These are tools. Does the tool do what I want with the least amount of friction? That’s what they care about.

Also how does Apples stance on one product in any way change the device you are using to post in any way? Are Apple thugs coming to your house destroying non-Apple tech? Of course not!

It always amuses me how Apple can simultaneously be irrelevant due to their market share and also be the greatest threat to open computing by their temerity at daring to have different computing models.

If you don’t like their computing model then don’t use it. Railing that they aren’t supporting your vision lockstep is pretty freaking arrogant.

Their market position is strong because they provide value that people desire. The market is not a zero sum game. Apples mere existence does diminish your computing experience. Indeed Apples existence and continually pushing computing in new areas has benefited everyone in the last 40 years - whether you use Apple or not. Just think where computing would be of the attitude that you were only a real computer user if you assembled it - at the component to board level, not just bolting pre-mad parts to a pre-made case - persisted? People criticized Apple for selling complete computers with the Apple II.

Your complaint isn’t that different.

Re: Undocumented arm64 ISA extension present on the Apple M1

#66

Post by simonh »

mhh__ wrote: post #7
lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

In the bigger picture Apple aren't really documenting anything for their new toys, which is not the end of the world but is a huge step back for openness. There is - as far as I can see - no long-form documentation for M1 other than patents. I already refuse to own apple products so I don't really have any skin in the game, but consider that if microsoft were like this the blind eye would not be turned - buy our new…

From an Apple perspective openness is a feature, not a goal in itself. Youre worrying about this or that specific ARM instruction, but Apple doesn't even want you to care whether it's ARM, or Intel, Or PowerPC, or whatever. It's an Apple system, part of the MacOS ecosystem and supported by Apple dev tools and power user features.

If that's not the world you are interested in, what are you even doing owning a Mac? Apple does not try to be all things to all people the way e.g. Microsoft has.

Re: Undocumented arm64 ISA extension present on the Apple M1

#67

Post by tcbawo »

rgovostes wrote: post #61
mhh__ wrote: post #51

Earlier quoted context omitted.

My point about the docs isn't the day-to-day stuff, but the things that cannot be machine generated - to write a good compiler you need to know the details of how the CPU is put together underneath. Intel will give you 800 pages on how to optimize for their current ISA (AMD will give you 45, but still)

As I understand it, Intel will also sell you a compiler that can optimize better than GCC because they know internal microarchitecture details. To me, that seems like a more clear-cut by-design conflict of interest between chip designer and user than these undocumented instructions.

Do you think Intel considers their compiler a profit center/growth market? Or are trying to offset the expense of maintaining their own compiler?

Re: Undocumented arm64 ISA extension present on the Apple M1

#68

Post by joseph_grobbles »

lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

Apple added special AMX instructions specifically for matrix operations. They added them back with the A13, and then improved them for the M1. These are primarily focused on machine learning training where you do backpropagation through huge matrix operations.

They provide a very wide coverage library set that works on all supported platforms optimally. You interact with AMX through those libraries, and direct usage is considered unsupported. Apple may completely change it with the next iteration, where they can just change those libraries and every arm's-length application will get those benefits for free.

Apple sells whole systems. They aren't selling CPUs for third parties, and there is no reason they need to encourage their own proprietary extensions. Indeed, it would be more evil if they were asking people to pepper their own code with this, instead of just using libraries that abstract you from the magic.

As a tiny, tiny vendor in the computing space -- as HN often assures us -- I'm not seeing the great evil many are claiming.

(indeed, of course this is downvoted but I chuckle that another comment implores that Apple is evil because this will lead to code and binaries that only work on Apple devices. Which is quite literally exactly the opposite of what Apple is doing, which is forcing use through optimized libraries, abstracting from their own proprietary extensions. People just love bitching)

Re: Undocumented arm64 ISA extension present on the Apple M1

#69

Post by vmception »

mhh__ wrote: post #7
lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

In the bigger picture Apple aren't really documenting anything for their new toys, which is not the end of the world but is a huge step back for openness. There is - as far as I can see - no long-form documentation for M1 other than patents. I already refuse to own apple products so I don't really have any skin in the game, but consider that if microsoft were like this the blind eye would not be turned - buy our new…

My life is so much better being in the Apple ecosystem.

Some of it was unintentional, but now its iPhone, Macbook Pro, Apple Watch, Airpods Pro, and IOT devices that use Homekit. I have an iPad but I use it the least.

Pre-Intel I used to make fun of "Apple fanboys". But aside from the niche and incompatibilities of the PowerPC architecture back then, that turned out to be a lot of other immaturities I had and was raised with.

I also used to use Android, but the "look how many advanced, poorly integrated and under maintained things I can do by myself" concept didn't stay appealing for very long.

Re: Undocumented arm64 ISA extension present on the Apple M1

#70

Post by notretarded »

joseph_grobbles wrote: post #68
lwhi wrote: post #2

I don't understand the significance of this. Could someone who does add some context?

Apple added special AMX instructions specifically for matrix operations. They added them back with the A13, and then improved them for the M1. These are primarily focused on machine learning training where you do backpropagation through huge matrix operations. They provide a very wide coverage library set that works on all supported platforms optimally. You interact with AMX through those libraries, and direct usage…

>These are primarily focused on machine learning training where you do backpropagation through huge matrix operations

How is this different from normal matrix operations?

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