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A comment on 1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5. Parent comment

Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by wtallis on Thursday December 18, 2025 @08:19PM (#46321175)
> Also, as the OP noted, this setup can support up to 4 Mac devices because each Mac must be connected to every other Mac

I do wonder where this limitation comes from, since on the M3 Ultra Mac Studios the front USB-C ports are also Thunderbolt 5, for a total of six Thunderbolt ports: https://www.apple.com/mac-studio/specs/

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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by QuantumNomad_ on Thursday December 18, 2025 @09:15PM (#46321581)
Jeff mentioned in the video that only three of the ports can be used for RDMA. But it’s unclear where that limitation is coming from.
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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by geerlingguy on Thursday December 18, 2025 @10:07PM (#46321874)
From my brief discussion with Exo/Apple, it sounds like that is just a limitation of this initial rollout, but it's not a hardware limitation.

Though, I am always leery to recommend any decisions be made over something that's not already proven to work, so I would say don't bet on all ports being able to be used. They very well may be able to though.

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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by sroussey on Thursday December 18, 2025 @10:12PM (#46321903)
I bet there is one piece of silicon per two ports.
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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by kappuchino on Friday December 19, 2025 @03:52AM (#46323680)
He corrected that in the comment section of the youtube video. Five is actually the maximum amount. He just didn't want to buy another one.
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Re:1.5 TB of VRAM on Mac Studio – RDMA over Thunderbolt 5 by re-thc on Friday December 19, 2025 @08:22AM (#46325546)
> He just didn't want to buy another one.

Wasn’t it loaned ie didn’t buy any at all?

Apple should have loaned enough to flex.

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