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Do the Thunderbolt 4 ports offer PCIe lanes on the z790 maximus hero?

Level 7

Looking at options for installing a third graphics card (potentially via an extension PCIe cable + mounting bracket via the third PCIe 4x 4x/4x

Alternatively, since the Thunderbolt 3 and 4 specifications include direct PCIe lane connection, I was also considering trying an external thunderbolt PCIe card enclosure.

I'm using them for deep learning purposes, and an authority on the subject did some testing, and found that 4 lane PCIe 3.0 only cut performance by like 5% or something.

Whatever the case, I've scoured all of the documentation I can find, and I can't find a clear picture of the PCIe situation for this board.

What I know is that my CPU offers 16x PCIe 5.0 lanes and 4 PCIe 4.0 lanes. And then the chipset, I believe, offers 24 additional PCIE lanes.

Main Question:
So, what I'm wondering, is whether I could add to my current 2x RTX 3090's in the first and second PCIE x16 slots (at x8/x8 w/ an NVLink bridge), then install, via a bracket and extender, a third GPU using 4 pcie lanes in the third PCIe x16 slot, and/or a third/fourth GPU via one of the thunderbolt 4 connectors and an external PCIe enclosure?


This is all deep learning, so the bandwidth should be fine... idk what the latency on Thunderbolt would be like vs the 3rd x16 slot... They both attach to the chipset lanes... idk. If anyone happens to have an answer for that too, I'd appreciate that info as well