Inside the M4 Apple Neural Engine, Part 1: Reverse Engineering

(maderix.substack.com)

228 points | by zdw 1 day ago

19 comments

  • LatencyKills 7 hours ago

    I worked on the Xcode team for years and know the lengths Apple goes to make this stuff difficult to figure out.

    I just wanted to say that you’ve done an excellent job and am looking forward to the 3rd installment.

    • RetpolineDrama 4 hours ago

      >I worked on the Xcode team for years

      Why did you guys remove the ability to detach the console and move it to another window?

    • blobbers 47 minutes ago

      Can someone help me understand when these neural engines kick in in open source software?

      I typically use python ML libraries like lightgbm, sklearn, xgboost etc.

      I also use numpy for large correlation matrices, covariance etc.

      Are these operations accelerated? Is there a simple way to benchmark?

      I see a lot of benchmarks on what look like C functions, but today in my jobs I rely on higher level libraries. I don't know if they perform any better on apple HW, and unless they have a flag like use_ane I'm inclined to think they do better.

      Of course chatgpt suggested I benchmark an Intel Mac vs. newer apple silicon. Thanks chatgpt, there's a reason people still hate AI.

      • zozbot234 32 minutes ago

        > when these neural engines kick in in open source software?

        It mostly doesn't because NPUs are bespoke and vendor-specific (which incents neglect by software devs working on open source numerics and ML/AI infrastructure), and the Apple ANE is no exception. Part of this effort is most likely about fixing that for the specific case of the Apple ANE.

      • Octoth0rpe 7 hours ago

        Part 2 has benchmarks: https://maderix.substack.com/p/inside-the-m4-apple-neural-en...

        6.6 FLOPS/W, plus the ability to completely turn off when not in use, so 0W at idle.

        • notepad0x90 2 hours ago

          I've been guilty of this myself, but every other comment here is like "What about <insert something unrelated to the topic but related to apple>".

          • zozbot234 2 hours ago

            Much of this information we already knew the very basics of from documentation of the M1/M2 ANE as accessed via bare-metal from Asahi Linux, but it's nice to see confirmation and it being explored in further depth. Note that according to OP Parts 1/2 for very large matmuls CoreML adds little to no overhead compared to the lower-level interface, so there seems to be plenty of scope for supporting ANE for prefill in local AI frameworks. Decode is generally memory-bandwidth limited unless context is very large, and the ANE requires special handling (converting from matmul to 1x1 convolution as described here is wasteful of memory bandwidth, as is potentially dequantizing to INT8/FP16 in memory) so it's less of a clear win.

            • eleventyseven 7 hours ago

              > Throughout this series, “we” refers to maderix (human) and Claude Opus 4.6 (by Anthropic) working as a pair. The reverse engineering, benchmarking, and training code were developed collaboratively

              Sure, "collaboratively." Why would I ever trust a vibe coded analysis? How do I, a non expert in this niche, know that Opus isn't pulling a fast one on both of us? LLMs write convincing bullshit that even fools experts. Have you manually verified each fact in this piece? I doubt it. Thanks for the disclaimer, it saved me from having to read it.

              • Anonbrit 6 hours ago

                Humans also write endless amounts of convincing bullshit, and have done since time immemorial. False papers and faked results have been a growing scourge in academia before LLMs were a thing, and that's just counting the intentional fraud - the reproducibility crisis in science, especially medical and psychological science, affects even the best designed and well intentioned of studies.

                Humans also make mistakes and assumptions while reverse engineering, so it will always need more engineers to go through the results, test things

                • withinboredom 6 hours ago

                  Claude likes to hide bad benchmarks from you, so it will show you where you are clearly winning. You even see some weird benchmarks in the article.

                • behnamoh 6 hours ago

                  It's insane that the source code of ANE is not available even to the MLX team, possibly one of the reasons Awni (MLX project head) left Apple.

                  • GeekyBear 6 hours ago

                    The recent news is that Apple is supposedly replacing the Core ML framework with an updated version that will make it easier to integrate third party LLMs into your apps.

                    > the company is also planning a few other software-based AI upgrades, including a new framework called Core AI. The idea is to replace the long-existing Core ML with something a bit more modern.

                    https://www.bloomberg.com/news/newsletters/2026-03-01/apple-...

                    • love2read 8 hours ago

                      This article was clearly written by a human (and AI) but still has a few "LLMisms" such as:

                      - The key insight - [CoreML] doesn't XXX. It YYY.

                      With that being said, this is a highly informative article that I enjoyed thoroughly! :)

                      The article links to their own Github repo: https://github.com/maderix/ANE

                      • walthamstow 7 hours ago

                        We've got about a year before so many people are interacting with LLMs on a daily basis that its style starts to reverse infect human speech and writing

                        • gogopromptless 19 minutes ago

                          It's already happened to me. I've started to have dreams where instead of some sort of interpersonal struggle the entire dream is just a chatbot UI viewport and I'm arguing with an LLM streaming the responses in. Which is super trippy when I become aware its a dream. In the old days I'd dream about playing chess against myself and lose which was quite bizzare feeling because my brain was running both players. But thats totally normal compared to having my brain pretend to be an LLM inside a dream.

                          • baxtr 5 hours ago

                            Great insight – Would you like to try and identify some specific "AI-isms" that you've noticed creeping into your own writing or your colleagues' emails lately?

                            • pixl97 7 hours ago

                              This said, there were people that talked like this before LLMs, it didn't develop this whole cloth.

                              • pcrh 4 hours ago

                                The article above doesn't read well, at all.

                                It's not my subject, but it reads as a list of things. There's little exposition.

                                • dylan604 5 minutes ago

                                  Gawd Damn LISTICLES!!!! And all of those articles that list in bullet points at the top of the article the summary of the article. And all of those people saying they don't want to read exposition, just give me the bullet points.

                                • DrScientist 6 hours ago

                                  Exactly. LLM's are mimics.

                                  People seem to be going around pointing out that people talk like parrots, when in reality it's parrots talk like people.

                                  • pixl97 5 hours ago

                                    I mean, it's both.

                                    Did you develop your own whole language at any point to describe the entire world? No, you, me, and society mimic what is around us.

                                    Humans have the advantage, at least at this point, of being a continuous learning device so we adapt and change with the language use around us.

                                • Angostura 7 hours ago

                                  My honest take? You're probably right

                                  • sholladay 6 hours ago

                                    You are absolutely right.

                                    Here is why you are correct:

                                    - I see what you did there.

                                    - You are always right.

                                • rafram 6 hours ago

                                  Also the Prior Art section, which has telltale repetition of useless verbs like "documenting," "providing insight into," and "confirming" on each line. This was definitely AI-written, at least in part.

                                  • tzs 3 hours ago

                                    Below are the items from that section. How should they be written to not look like an AI?

                                    > hollance/neural-engine — Matthijs Hollemans’ comprehensive community documentation of ANE behavior, performance characteristics, and supported operations. The single best existing resource on ANE.

                                    > mdaiter/ane — Early reverse engineering with working Python and Objective-C samples, documenting the ANECompiler framework and IOKit dispatch.

                                    > eiln/ane — A reverse-engineered Linux driver for ANE (Asahi Linux project), providing insight into the kernel-level interface.

                                    > apple/ml-ane-transformers — Apple’s own reference implementation of transformers optimized for ANE, confirming design patterns like channel-first layout and 1×1 conv preference.

                                • mattlangston 7 hours ago

                                  The future is bright for software engineers.

                                  The big takeaway isn't reverse engineering the ANE per se, but what Manjeet could do with his software engineering skills when accelerated by AI.

                                  This is a good example of the present state of software engineering. Not future state - present state.

                                  • grey-area 3 hours ago

                                    If only they could fix the iOS autocomplete, which is getting worse with every iteration.

                                    • giancarlostoro 5 hours ago

                                      Reverse Engineering with AI is only going to get better. I have seen some crazy things friends of mine have done with Claude alone. Let's just says SaaS isn't the only industry that could one day suffer.

                                      • mayhemducks 5 hours ago

                                        I never realized just how much hardware engineering Apple dedicated to enabling people to type faster with their thumbs!

                                        • kamranjon 7 hours ago

                                          I have always wondered if the neural engine could be used for training - pretty excited for part 3 of this to see if the juice is actually worth the squeeze

                                          • juancn 5 hours ago

                                            In principle most if not all inference hardware should be usable for training.

                                            Efficiency is the question.

                                          • daoistmonk 6 hours ago

                                            Tangential: Is anyone doing something similar to accelerate the support matrix of Linux on anything higher than M2?

                                            • msie 5 hours ago

                                              I remember the good old days when Apple was desperate for developers and produced great documentation and there were a lot of great 3rd-party books too. You can't just give out awards in hopes that someone will make that great app.

                                              • pstuart 4 hours ago

                                                Yeah, the Inside Macintosh guides were epic.

                                              • ericol 3 hours ago

                                                > human intuition driving the exploration

                                                This, a thousand times this.

                                                For me, what AI brings is augmented humans. Just as we don't calculate on paper anymore, what is the reason of doing things by hand when a machine in X times better.

                                                Want to code by hand, as artisans of old? Suit yourself.

                                                I, for one, love the smell of burning chrome.

                                                • pklausler 3 hours ago

                                                  If "AI" were doing anything more than repeating content from the web without attribution, I might agree with you.

                                                • FL33TW00D 5 hours ago

                                                  Unreadable Claude slop

                                                  • poszlem 8 hours ago

                                                    Genuine question, not trying to throw a shade or anything, but are those cores actually useful with the state of apple intelligence being what it is?

                                                    • rahkiin 8 hours ago

                                                      They are also used by ML models that are deeply integrated in macos and ios without you knowing. Like object and text detection in images.

                                                      • geerlingguy 7 hours ago

                                                        And help in Photos, Final Cut Pro, and other apps.

                                                        • willis936 6 hours ago

                                                          I wish they would (or wouldn't if they are) hook it up to the ios keyboard.

                                                        • dagmx 7 hours ago

                                                          If you strip away the branding, Apple has and continues to ship a ton of algorithms that likely use the ANE and end users can use CoreML to do the same.

                                                          Just some things that people will likely take for granted that IIRC Apple have said use the ANE or at least would likely benefit from it: object recognition, subject extraction from images and video, content analysis, ARKit, spam detection, audio transcription.

                                                          • sroussey 6 hours ago

                                                            Don’t forget FaceID and many of the image manipulation.

                                                            And while everyone else went to more powerful giant LLMs, Apple moved most of Siri from the cloud to your device. Though they do use both (which you can see when Siri corrects itself during transcription—you get the local Siri version corrected later by the cloud version).

                                                          • stetrain 8 hours ago

                                                            Apple's OSes run a lot of local ML models for many tasks that aren't branded as Apple Intelligence, and they have done so for many years now.

                                                            • llm_nerd 8 hours ago
                                                              • malshe 5 hours ago

                                                                This is a nice article. Thanks for sharing.

                                                              • esafak 8 hours ago

                                                                You can convert your own ML models to MLX to use them; Apple Intelligence is not the only application.

                                                                • nullstyle 8 hours ago

                                                                  MLX does not run on NPUs AFAIK; just gpu and cpu. You have to use CoreML to officially run code on the neural engine.

                                                                  • mirsadm 8 hours ago

                                                                    Even then there is no transparency on how it decides what runs on the ANE/GPU etc

                                                                    • sroussey 6 hours ago

                                                                      Correct. OS level stuff get first priority, so you can’t count on using it.

                                                                      • znagengast 4 hours ago

                                                                        Turns out third party actually gets priority for ANE