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iPhone 17 Pro Demonstrated Running a 400B LLM

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Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#131
post #6

A year ago this would have been considered impossible. The hardware is moving faster than anyone's software assumptions.

This isn't a hardware feat, this is a software triumph. They didn't make special purpose hardware to run a model. They crafted a large model so that it could run on consumer hardware (a phone).

both, tbh

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#132
Apple’s unified memory architecture plays a huge part in this. This will trigger a large scale rearchitecture of mobile hardware across the board. I am sure they are already underway.

I understand this is for a demo but do we really need a 400B model in the mobile? A 10B model would do fine right? What do we miss with a pared down one?

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#133

I have some macro opinions about Apple - not sure if I'm correct, but tell me what you think. Apple has always seen RAM as an economic advantage for their platform: Make the development effort to ensure that the OS and apps work well with minimal memory and save billions every year in hardware costs. In 2026, iPhones still come with 8Gb of RAM, Pro/Max come with 12Gb. The problem is that AI (ML/LLM training and infer…

RAM is just too expensive. We need to bring back non-DRAM persistent memory that doesn't have the wearout issues of NAND.

multiple NAND, and apple already used it in Mac Studio. Plus better cooling

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#134

Earlier quoted context omitted.

> Though iPhone Pro has very limited RAM (12GB total) which you still need for the active part of the model. This is why mixture of experts (MoE) models are favored for these demos: Only a portion of the weights are active for each token.

Yes but most people are still running MoE models with all experts loaded in RAM! This experiment shows quite clearly that some experts are only rarely needed, so you do benefit from not caching every single expert-layer in RAM at all times.

I’m so confused in these comments right now — I thought you had to load an entire MoE model and sparseness just made it so you can traverse the model more quickly.

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#135

Apple’s unified memory architecture plays a huge part in this. This will trigger a large scale rearchitecture of mobile hardware across the board. I am sure they are already underway. I understand this is for a demo but do we really need a 400B model in the mobile? A 10B model would do fine right? What do we miss with a pared down one?

> Apple’s unified memory architecture plays a huge part in this. This will trigger a large scale rearchitecture of mobile hardware across the board. I am sure they are already underway.

Putting the GPU and CPU together and having them both access the same physical memory is standard for phone design.

Mobile phones don't have separate GPUs and separate VRAM like some desktops.

This isn't a new thing and it's not unique to Apple

> I understand this is for a demo but do we really need a 400B model in the mobile? A 10B model would do fine right? What do we miss with a pared down one?

There is already a smaller model in this series that fits nicely into the iPhone (with some quantization): Qwen3.5 9B.

The smaller the model, the less accurate and capable it is. That's the tradeoff.

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#137

I have some macro opinions about Apple - not sure if I'm correct, but tell me what you think. Apple has always seen RAM as an economic advantage for their platform: Make the development effort to ensure that the OS and apps work well with minimal memory and save billions every year in hardware costs. In 2026, iPhones still come with 8Gb of RAM, Pro/Max come with 12Gb. The problem is that AI (ML/LLM training and infer…

Models on the phone is never going to make sense.

If you're loading gigabytes of model weights into memory, you're also pushing gigabytes through the compute for inference. No matter how you slice it, no matter how dense you make the chips, that's going to cost a lot of energy. It's too energy intensive, simple as.

"On device" inference (for large LLM I mean) is a total red herring. You basically never want to do it unless you have unique privacy considerations and you've got a power cable attached to the wall. For a phone maybe you would want a very small model (like 3B something in that size) for Siri-like capabilities.

On a phone, each query/response is going to cost you 0.5% of your battery. That just isn't tenable for the way these models are being used.

Try this for yourself. Load a 7B model on your laptop and talk to it for 30 minutes. These things suck energy like a vacuum, even the shitty models. A network round trip costs gets you hundreds of tokens from a SOTA model and costs 1 joule. By contrast, a single forward pass (one token) of a shitty 7b model costs 1 joule. It's just not tenable.

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#138
post #9
post #8

It’s 400B but it’s mixture of experts so how many are active at any time?

Looks like it's Qwen3.5-397B-A17B so 17B active. https://github.com/Anemll/flash-moe/tree/iOS-App

Still pretty good considering 17B is what one would run on a 16GB laptop at Q6 with reasonable headroom

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#139

Earlier quoted context omitted.

> Though iPhone Pro has very limited RAM (12GB total) which you still need for the active part of the model. This is why mixture of experts (MoE) models are favored for these demos: Only a portion of the weights are active for each token.

Yes but most people are still running MoE models with all experts loaded in RAM! This experiment shows quite clearly that some experts are only rarely needed, so you do benefit from not caching every single expert-layer in RAM at all times.

That's not what this test shows. It's just loading the parts of the model that are used in an on-demand fashion from flash.

The iPhone 17 Pro only has 12GB of RAM. This is a -17B MoE model. Even quantized, you can only realistically fit one expert in RAM at a time. Maybe 2 with extreme quantization. It's just swapping them out constantly.

If some of the experts were unused then you could distill them away. This has been tried! You can find reduced MoE models that strip away some of the experts, though it's ony a small number. Their output is not good. You really need all of the experts to get the model's quality.

Re: iPhone 17 Pro Demonstrated Running a 400B LLM

#140
post #102

Earlier quoted context omitted.

Probably the one elephant in the roomy thing that matters: failing to say they don't know/can't answer

Claude does it all the time, in my experience.

Same here, it's even told me "I don't have much experience with this, you probably know better than me, want me to help with something else?".
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