Intel XL710-QDA2 in PCIe 4.0 x2 Slot?

Networking
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I want to directly connect two computers using two Intel XL710-QDA2 40Gbps PCIe 3.0 x8 cards. However, the only slot I have available on my MSI x670-P Wi-Fi motherboard is a PCIe 4.0 x 2 slot (the physical slot size is x16).

If the card I would put in the other computer is in a PCIe 3.0 x 16 slot, does this mean I will get 10 Gbps speeds (since the Intel card is x8 but would be limited to a x2 on the MSI motherboard)? Or would it not function at all, or at a different speed?

I did a similar test on these computers using Mellanox Connect-X2 10G SFP+ cards and I was getting about 500 MB/sec in the PCIe 4.0 x2 slot, which was higher than the 250 I expected given those cards are PCIe 2.0 x8 (I think).

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You will have the lowest protocol that either the card or the motherboard supports with the physical amount of lanes that are present. PCIe3.0x8 card in PCIe4.0x2 slot will negotiate a PCIe3.0x2 connection. PCIe3.0x1 is 985MB/s so twice that would amount to about 16190Mbits.

This all is based on what you gave me, I want to note that I’ve never seen a PCIe x2 connection though, it’s either x1, x4, x8 or x16. But maybe in the space of professional server equipment x2 also does exist, I am not sure.

Also PCIe2.0x1 is 500 MB/s!

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