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
Yea you may lose performance or may not, depends how the chip works on the actual pcie card. (Even if the slot has more than enough bandwidth at x1)
You can easily do a performance test after plugging it in though. Typically even an x8 interface will work with just x1 pcie connectors just slower. Even if that x1 interface is several generations later and has more bandwidth than that x8 needs lol
some ramblings of why just having the physical slots doesn’t always mean ___ can be found on this completely unrelated repo: https://github.com/magic-blue-smoke/Dual-Edge-TPU-Adapter (might be in an issue thread too unfortunately but he has more info here on how bandwidth works at that level than any other sites)
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
Get a slot adapter first, to male sure your use case works before doing the physical mods others are talking about
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
They all have to work (at least to an extent) using only x1. It’s part of the PCIe spec.
Missing pins are actually extremely common. If your board has a slot that’s x16 (electrically x8), which is very common for a second video card, take a closer look. Half the pins in the slot aren’t connected. It has the full slot to make you feel better about it, and it provides some mounting stability, but it’s electrically the same as an x8 that’s open.
I see. Thanks
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
If you don’t want to risk modifying the slot, try one of the cheap PCIe risers on amazon and send it back if it doesn’t work. You will need a case with a couple of extra slots under the motherboard in order to fit the riser in there though.
It will run slower, but that probably won’t be an issue unless you plan to max out all 4 ports simultaneously.
I did this but buying these on Amazon is scary. Try to find one that won’t burn your house down.
Yeah, I definitely wouldn’t recommend putting something power hungry like a GPU in one of these. A NIC will be fine though.
Even maxing out the ports won’t be a problem. Even 6 gigabit ports don’t saturate a PCIe Gen 3 X1 slot in terms of bandwidth. But will the card work at all if all the physical pins are not connected electrically to the slot?
I cannot see any decent PCIE X1 to X16 risers on amazon. Everything is USB based which I don’t want
They are not USB based, they just happen to use a USB 3 cable to carry the PCIe signals.
Oh. I thought they were using USB. Thanks
USB the protocol, or just uses a USB cable? If it’s not using the protocol, the cables are a cheap way of getting cables of a certain spec.
I thought they were using the USB protocol. Thanks
Pretty sure if you put a PCIe 3.0 card in a 4.0 slot the slot will drop to 3.0, and 1 PCIe 3.0 lane probably isn’t going to work great with a card meant for 4 of them.
The card only needs PCIE Gen 3 X2 == PCIE Gen 4 X1 in terms of bandwidth. I was hoping to fit it into the slot since it meets the bandwidth requirements
An x1 slot is an x1 slot, the PCIe version will downgrade but there will still only be one lane because that’s all the slot physically has connections for. It will effectively be a PCIe 3.0 x1 slot.
Technically the slot is PCIe Gen 4 x1, but I understand. TBH PCIe gen 3 X1 is fine too, that’s more than 6 port Gigabit cards can saturate anyway.
I don’t think you do.
A x1 will fit in a x4 but not the other way around.
How would I do it then? The card doesn’t exactly need PCIE gen 3 X4, at the most it needs PCIE Gen 3 X2 == PCIE Gen 4 X1 in terms of bandwidth.
In terms of physical connections you’ve said that the card needs the x4. Not sure what there is to say further.
Can’t get a 30 cm ruler into a 15 cm pencil case.
Maybe I’ve totally misunderstood your post.
This is false when it comes to me to PCIe, as mentioned elsewhere in this thread.
Most motherboards have cutouts on one end of the PCIe x1/x4 slots, for exactly this situation. If not, and you want to be adventurous, you can cut the plastic of the slot and it’ll work fine.
If the card is PCIe 3.0 x4, and the slot is PCIe 4.0 x1, the card will run at PCIe 3.0 x1. But it’ll work.
Up voted
I stand corrected. Thanks for the heads up… Really wasn’t expecting that.
Apologies to OP. I don’t know how to reference users: marauding_gibberish142@lemmybdzero
Thanks
Does one good to be challenged (at least) occasionally.
I learned something new.
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?
Potentially the same thing, assuming PCIe 2 x1 provides enough bandwidth.
Pcie 2.0x1 would have a theoretical max of 4gbit/s so it would probably only handle 3.5 gigabit of connections simultaneously.
