this post was submitted on 13 Jul 2023
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PCIE M.2 adapter cards (self.buildapc)
submitted 1 year ago by Glemek to c/buildapc
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I'm considering adding more storage to my PC, and came across PCIe to M.2 adapter cards. I was wondering if performance would suffer on the adaptor card vs directly on the mobo? The M.2 slot is pretty much a PCIe x4 slot, so a a PCIe x16 should be able to drive 4 M.2 SSDs without issue right?

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[–] DoomBot5 4 points 1 year ago* (last edited 1 year ago) (1 children)

Correct. Performance shouldn't be an issue if you confirm the following:

  • verify the 16x slot actually has 16 lanes going to it. Some motherboards only run the full lane count to the top slot.
  • verify your motherboard supports 4x/4x/4x/4x pcie bifurcation for 3-4 drives, or at least 8x/8x or 4x/4x for 2 drives. Without this feature, only 1 drive will show up regardless of how many you put in there.
  • make sure you have enough pcie lanes to support the number of cards you want. In consumer hardware pcie lanes are often shared among several devices that are plugged in.

As an alternative to the 2nd one, you can buy very expensive pcie adapter cards that have a chip onboard, saving you from needing bifurcation support.

[–] Glemek 1 points 1 year ago* (last edited 1 year ago) (1 children)

Thanks for this, I didn't know about the bifurcation or total PCIe lanes at all. It looks like my mobo supports 8x/8x on the 2nd 16x slot which makes it a little less attractive than the potential of eventually jamming an additional 4 M.2 drives.

I gotta look a bit more into the PCIe lanes though, I don't feel like I really understand what I actually have available with my hardware.

Edit: spelling

[–] DoomBot5 2 points 1 year ago

You're welcome. It's a big gotcha that people aren't aware of until they get into homelabbing.

[–] [email protected] 3 points 1 year ago

Performance would also depend on if your x16 slots are PCIe gen 3 or gen 4. Gen 4 is backwards compatible, but don't overspend on gen 4 SSDs if your mobo is only gen 3.