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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by zozbot234 on Thursday December 18, 2025 @06:44PM (#46320429)
> Neural accelerators to get prompt prefill time down.

Apple Neural Engine is a thing already, with support for multiply-accumulate on INT8 and FP16. AI inference frameworks need to add support for it.

> this setup can support up to 4 Mac devices because each Mac must be connected to every other Mac!!

Do you really need a fully connected mesh? Doesn't Thunderbolt just show up as a network connection that RDMA is ran on top of?

Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by pdpi on Thursday December 18, 2025 @07:52PM (#46320971)
> Do you really need a fully connected mesh? Doesn't Thunderbolt just show up as a network connection that RDMA is ran on top of?

If you daisy chain four nodes, then traffic between nodes #1 and #4 eat up all of nodes #2 and #3's bandwidth, and you eat a big latency penalty. So, absent a switch, the fully connected mesh is the only way to have fast access to all the memory.

Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by rbanffy on Friday December 19, 2025 @07:23AM (#46325060)
Can’t you make bandwidth reservations and optimise data location to prefer comms between directly connected nodes over one or two-hop paths?
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by KeplerBoy on Friday December 19, 2025 @07:47AM (#46325222)
Sure, one could think of some kind of pipeline parallelism where you only need a fast transfer to the next step in the model and that would boost throughput but not increase model size.
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by Dylan16807 on Friday December 19, 2025 @12:53PM (#46328748)
Obviously don't daisy chain, that wastes ports so badly. But if you connect 4 nodes into a loop, it goes fine. Relaying only adds 33% extra traffic. And what specifically are the latency numbers you have in mind?

If you have 3 links per box, then you can set up 8 nodes with a max distance of 2 hops and an average distance of 1.57 hops. That's not too bad. It's pretty close to having 2 links each to a big switch.

Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by liuliu on Thursday December 18, 2025 @07:14PM (#46320698)
They were talking about neural accelerators (a silicon piece on GPU): https://releases.drawthings.ai/p/metal-flashattention-v25-w-...
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by csdreamer7 on Thursday December 18, 2025 @07:21PM (#46320758)
> Apple Neural Engine is a thing already, with support for multiply-accumulate on INT8 and FP16. AI inference frameworks need to add support for it.

Or, Apple could pay for the engineers to add it.

Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by ls612 on Thursday December 18, 2025 @08:07PM (#46321090)
Apple already paid software engineers to add Tensorflow support for the ANE hardware.
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by fooblaster on Thursday December 18, 2025 @06:54PM (#46320515)
Might be helpful if they actually provided a programming model for ANE that isn't onnx. ANE not having a native development model just means software support will not be great.
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by sroussey on Thursday December 18, 2025 @10:13PM (#46321917)
onnx supports CoreML, is that how?
Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by solarkraft on Thursday December 18, 2025 @11:12PM (#46322199)
How much of an improvement can be expected here? It seems to me that in general most potential is pretty quickly realized on Apple platforms.