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macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

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Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#61
post #41

Is there any way to connect DGX Sparks to this via USB4? Right now only 10GbE can be used despite both Spark and MacStudio having vastly faster options.

Sparks are built for this and actually have Connect-X 7 NICs built in! You just need to get the SFPs for them. This means you can natively cluster them at 200Gbps.

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#62

Can we get proper HDR support first in macOS? If I enable HDR on my LG OLED monitor it looks completely washed out and blacks are grey. Windows 11 HDR works fine.

AI is arguably more important than whatever gaming gimmick you're talking about.

[flagged]

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#63

This doesn’t remotely surprise me, and I can guess Apple’s AI endgame: * They already cleared the first hurdle to adoption by shoving inference accelerators into their chip designs by default. It’s why Apple is so far ahead of their peers in local device AI compute, and will be for some time. * I suspect this introduction isn’t just for large clusters, but also a testing ground of sorts to see where the bottlenecks l…

The bandwidth of rdma over thunderbolt is so much faster (and lower latency) than Apple's system of mostly-wireless devices, I can't see how any learnings here would transfer.

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#64
post #41

Is there any way to connect DGX Sparks to this via USB4? Right now only 10GbE can be used despite both Spark and MacStudio having vastly faster options.

Sparks are built for this and actually have Connect-X 7 NICs built in! You just need to get the SFPs for them. This means you can natively cluster them at 200Gbps.

That doesn't answer the question, which was how to get a high-speed interconnect between a Mac and a DGX Spark. The most likely solution would be a Thunderbolt PCIe enclosure and a 100Gb+ NIC, and passive DAC cables. The tricky part would be macOS drivers for said NIC.

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#65

dang I wish I could share md tables. Here’s a text edition: For $50k the inference hardware market forces a trade-off between capacity and throughput: * Apple M3 Ultra Cluster ($50k): Maximizes capacity (3TB). It is the only option in this price class capable of running 3T+ parameter models (e.g., Kimi k2), albeit at low speeds (~15 t/s). * NVIDIA RTX 6000 Workstation ($50k): Maximizes throughput (>80 t/s). It is sup…

For $50K, you could buy 25 Framework desktop motherboards (128G VRAM each w/Strix Halo, so over 3TB total) Not sure how you'll cluster all of them but it might be fun to try. ;)

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#66
post #11

Earlier quoted context omitted.

It’s gonna suck if all the good Macs get gobbled up by commercial users.

it's not like regular people can afford this kind of Apple machine anyway.

It’s just depressing that the “PC in every home” era is being rapidly pulled out from under our feet by all these supply shocks.

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#67
post #30
post #3

I follow the MLX team on Twitter and they sometimes post about using MLX on two or more joined together Macs to run models that need more than 512GB of RAM. A couple of examples: Kimi K2 Thinking (1 trillion parameters): https://x.com/awnihannun/status/1986601104130646266 DeepSeek R1 (671B): https://x.com/awnihannun/status/1881915166922863045 - that one came with setup instructions in a Gist: https://gist.github.com/…

I’m hoping this isn’t as attractive as it sounds for non-hobbyists because the performance won’t scale well to parallel workloads or even context processing, where parallelism can be better used. Hopefully this makes it really nice for people that want the experiment with LLMs and have a local model but means well funded companies won’t have any reason to grab them all vs GPUs.

The lack of official Linux/BSD support is enough to make it DOA for any serious large-scale deployment. Until Apple figures out what they're doing on that front, you've got nothing to worry about.

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#69
post #50

Earlier quoted context omitted.

For a bit more context, those posts are using pipeline parallelism. For N machines put the first L/N layers on machine 1, next L/N layers on machine 2, etc. With pipeline parallelism you don't get a speedup over one machine - it just buys you the ability to use larger models than you can fit on a single machine. The release in Tahoe 26.2 will enable us to do fast tensor parallelism in MLX. Each layer of the model is…

But that's only for prefilling right? Or is it beneficial for decoding too (I guess you can do KV lookup on shards, not sure how much speed-up that will be though).

Even if it wasn't outright beneficial for decoding by itself, it would still allow you to connect a second machine running a smaller, more heavily quantized version of the model for speculative decoding which can net you >4x without quality loss

Re: macOS 26.2 enables fast AI clusters with RDMA over Thunderbolt

#70
post #11
post #9

It would be incredibly ironic if, with Apple's relatively stable supply chain relative to the chaos of the RAM market these days (projected to last for years), Apple compute became known as a cost-effective way to build medium-sized clusters for inference.

It’s gonna suck if all the good Macs get gobbled up by commercial users.

Outside of YouTube influencers, I doubt many home users are buying a 512G RAM Mac Studio.
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