Undocumented arm64 ISA extension present on the Apple M1

Post by mhh__ » Mon, Dec 28, 2020, 6:32 PM UTC

whatshisface wrote: post #10

mhh__ wrote: post #7

Earlier quoted context omitted.

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…

> The fact that they can be like this is really proof that their market position is much stronger than most HNers seem to think it is. Elsewhere on the HN front page is a computer made with a Russian internal CPU. The CPU has a custom ISA based on x86, and isn't open. The documentation is poor, and nobody has the source code for the compiler. It's also about 5 years behind the state of the art in x86. How can a produ…

Post by bnt » Mon, Dec 28, 2020, 6:45 PM UTC

mhh__ wrote: post #12

whatshisface wrote: post #10

Earlier quoted context omitted.

> The fact that they can be like this is really proof that their market position is much stronger than most HNers seem to think it is. Elsewhere on the HN front page is a computer made with a Russian internal CPU. The CPU has a custom ISA based on x86, and isn't open. The documentation is poor, and nobody has the source code for the compiler. It's also about 5 years behind the state of the art in x86. How can a produ…

The Russian CPU isn't surviving in a market

Post by giantrobot » Mon, Dec 28, 2020, 6:47 PM UTC

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…

Post by emteycz » Mon, Dec 28, 2020, 6:56 PM UTC

tenebrisalietum wrote: post #17

MichaelZuo wrote: post #9

Earlier quoted context omitted.

The implication I assume that there would be pushback on Microsoft for doing the same would be because of the possibility of nefarious undocumented changes. What possibly nefarious things could an undocumented ISA extension do?

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…

Post by spamizbad » Mon, Dec 28, 2020, 7:07 PM UTC

whatshisface wrote: post #10

mhh__ wrote: post #7

Earlier quoted context omitted.

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…

> The fact that they can be like this is really proof that their market position is much stronger than most HNers seem to think it is. Elsewhere on the HN front page is a computer made with a Russian internal CPU. The CPU has a custom ISA based on x86, and isn't open. The documentation is poor, and nobody has the source code for the compiler. It's also about 5 years behind the state of the art in x86. How can a produ…