this post was submitted on 27 Mar 2025
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How do I fit a network card with a physical x4 slot into an x1 slot? (lemmy.dbzer0.com)
submitted 1 week ago* (last edited 1 week ago) by marauding_gibberish142@lemmy.dbzer0.com to c/selfhosted@lemmy.world
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I'm looking at quad port 2.5Gbe Intel PCIe cards. These cards seem to be mostly x4 physically (usually PCIe gen 3) whilst I have a PCIe Gen4 X1 slot, which is more the theoretical bandwidth that the card can support. The card needs at the most PCIE Gen 3 X2 == PCIE Gen 4 X1 in terms of bandwidth.

How do I fit the card into a PCIe x1 slot? Won't it lose performance if all the pins are not connected to the physical PCIe connector? Is there a PCIe x1 riser that the community likes that is somewhat affordable?

Thanks

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[–] BombOmOm@lemmy.world 26 points 1 week ago* (last edited 6 days ago) (2 children)

File a small slit in the end of the slot so the card fits into it, but runs past the back. The card will run at Gen 3 x1 speed, but otherwise work properly.

Many motherboards even come with the end of the PCIe slots open for this exact purpose.

Edit: Gen 3 x1 runs at almost a full GB/s, so a 2.5Gb/s card (notice the change in size of the "B") should have more than enough bandwidth on Gen 3 x1, even at 2.5Gb/s full duplex.

[–] litchralee@sh.itjust.works 16 points 6 days ago

A word of caution for anyone cutting out the slot: make sure there aren't other instructions, like capacitors, ICs, and NVMe drives in the way of where the PCIe card will be.

The manufacturers that have the slot pre-cut will have already reserved the space, but even then, it's on you to check that it's suitable for a x16 if they only reserved space for a x8 card.

[–] marauding_gibberish142@lemmy.dbzer0.com 4 points 6 days ago (1 children)

I'll likely go for a 4 or 6 gigabit port card, so PCIe gen 3 x1 is not a problem. Am I correct in understanding that the card will run at PCIe gen 3 X1 if I do this?

What can I do if the card is PCIe gen 2 x8? These cards from Silicom are really cheap on ebay

[–] BombOmOm@lemmy.world 1 points 6 days ago* (last edited 6 days ago) (1 children)

Am I correct in understanding that the card will run at PCIe gen 3 X1 if I do this?

Correct. The situation you described in the original post would result in Gen 3 x1 speeds.

The interface will always default to the fastest standard that both sides can support. If one is gen 2 and the other is gen 4, gen 2 is the highest that can be supported. If one side is x8 and the other is x4, x4 is the highest that can be supported.

What can I do if the card is PCIe gen 2 x8?

If you put a Gen 2 x8 card in a Gen 4 x1 slot, you will get a Gen 2 x1 link.