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
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.
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.
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
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.
Alright thanks
Hand saw?
I don’t want to cut the card
Cut the slot? Or desolder it and replace it with one with an open back.
The slot is open. I’m just wondering whether the card will work properly in that slot since all the pins won’t be attached. PCIe Gen 3 X1 bandwidth is more than enough for it
Then plug it in and go to town. Either it’ll work, or it won’t. Some cards get unhappy about missing pins, but it’s really just luck of the draw.
There’s another situation. There are older (and cheaper cards) which are PCIe gen 2 x8. Unfortunately, pcie gen 2 x1 is not going to suffice. What would I have to do to get this older kind of card to work? Do you have any reliable PCIe x1 to x16 risers in mind?
You also just plug it in. But again, no guarantee it’ll work. Even if you get a riser, most of them are just physical adapters. The fancier server ones do have some brain to them, but I don’t know if it would help.
You could also just sidestep the problem and use some USB adapters.
PCIe to USB and back to PCIe like what the miners use? Isn’t that unreliable long-term?
I think you’re missing the point of a riser. I’d the motherboard only has a 3.0x1 port, plugging in an x16 riser means it’ll still only be x1 electrically, but it can physically fit larger cards. If the back of the slot is open already there not much point of using a riser since you can physically fit larger cards already.
- If your board has pcie 3.0x1, you want the pcie 3.0 card. Running at 2.0x1 reduces speed by 50%
My board has PCIe gen 4 x1, but unfortunately there’s a really cheap card with 6 ethernet ports but PCIe gen 2 X8
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If your card has an x4 pinout, then it probably needs the additional bandwidth. Plugging it into an x1 slot (if it was possible) would slow down the network traffic. Get a better motherboard with an x4 slot on it so you can use the hardware you want. or find something else that will fit your computer.
Honestly even the 1Gb quad port card I have requires an x4 slot, although I saw some dual-port 2.5Gb x1 cards on ebay. Maybe you could just use two of those?
It doesn’t need that kind of bandwidth. 6 gigabit ports cannot saturate pcie gen 3 x1 in terms of bandwidth anyway.
What do I do if the card is PCIe gen 2 x8 though?
