PCIe x4 card in a x1 slot


I have a board with an x1 slot empty. Il have the need to add a dual port NIC which come on a x4 card.
I also need to use a riser for my low profile home system, like these http://www.ameri-rack.com/ARC1-PEX16_m.html.

These risers accept x4 cards and fit in an x1 slot.

Is that supposed to work? I thought that you could insert a x1 card in a x4 slot, but not a x4 card in a x1 slot.
Am I correct in this?

Many thanks for your PCIe insights!

Kind regards, Joost
7 answers Last reply
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  1. If you can physically plug it in fine, then it will work. However, it will function at the x1 speed.
  2. Well, you are correct. Physically you can insert a 1x card into a 4x slot and it will work fine, but the 4x connector won't fit in a 1x slot (for a reason) and likely will not work even with the adapter. The link you provided comes up to a 404 Not Found HTML error for me but, I've heard about those risers before. Think about it this way. Your trying to plug in a 220 volt appliance into a 110 socket.
  3. The original link gives a 404.
    Here's the right one
  4. PCI-Express is split into lanes to provide bandwidth. If you shove a device into a one lane slot that is designed to be in a 4 lane slot, something is bound to not work right. It's like shoe-horning a size 9 shoe onto a size 12 foot.
  5. OK. Thanks for your insight.

    I'm fine with the idea of getting only 10Mb/s performance per port. My question is really wether it will work? Does a x4 card have an idea of the slot it's plugged in or is anything beyond x1 just "lanes"?
  6. It should work if the specifications are implemented correctly. Lanes are negotiated by both parties.
    A PCIe 1.0 x1 link is roughly equivalent to a PCI link. So maybe 150-200MB/s is still achievable (250MB/s on paper), considering that the x1 link is never shared. And if PCIe 2.0 can be used, then the paper limit goes to 500MB/s.
  7. That's helpfull. I appreciate it. I'll buy it and let you know wether it works.
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