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Since there are adapters to adapt M.2 to PCIe x4, I was wondering if such an adapter can be used to connect other PCIe devices like network interfaces or USB controllers to the system?

Are there any special features that need to be supported by the motherboard for this to work (besides having a M.2 connector that is hooked up to PCIe of course).

M.2 to PCIe adapter

comfreak
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    Your question title does not match your question within the body of your question. Can you clarify what your question is exactly? Your title indicates the question is "can I purchase an M2 to PCIe adapter", but your question body, seems to indicate you already know the answer to this question. You then speak very briefly about USB controllers and LAN network adapters, which have very little to do with M.2, since I have never seen USB controllers or LAN network adapters in a M.2 configuration – Ramhound May 31 '17 at 18:55
  • @Ramhound No, the title didn't indicate if I can purchase an adapter, obviously I can do that, since that is where I got the picture from. The question is if it is possible to adapt the interface also electrically and logically (as in circuit logic). Nonetheless, I reworded the title. – comfreak May 31 '17 at 19:26
  • I read, "Can I adapt M.2 to PCIe?", as something else entirely then. – Ramhound May 31 '17 at 20:17

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An M.2 slot basically has 4x PCIe V3.0 and a regular SATA port in 1 connector.
Those adapters break out the PCIe lanes and feed them into a normal PCIe 4x connector which should be able to take any PCIe 1x and 4x card (provided you can physically fit that somehow it in your PC case).

Whether it will actually work properly??? Maybe...

The PCIe lanes are a very high-speed bus. Adding more wiring length (which this converter does) to that might cause problems with electrical interference.
Some PCI-e cards may be fine with it. Others may not. Trail and error is the only way to say for sure.
If I were to guess: The faster the PCIe device put in such a converter the more potential for trouble.
A PCIe 1x serial adapter is probably fine. A 10 Gb/s network card probably not.

Tonny
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  • Thanks for your useful input! I am actually not that worried about interference though, since there are riser cables for PCIe x16 that are several inches long: http://gg.gg/pcierisercable – Now the question is if there are restrictions to this due to the motherboard's BIOS/UEFI or if the interface's lanes are wired like all the other PCIe connections. – comfreak May 31 '17 at 19:51
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    @comfreak I know those risercables... And I have similar experience with them. It is a bit trail and error. Worst problem is that failures can be intermittent/rare and therefor the occasional glitch or even bluescreen is not linked to the riser. Can make for very nasty troubleshooting. – Tonny May 31 '17 at 19:54
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    Wiring as far as bios is concerned is just regular PCIe as far as I know. – Tonny May 31 '17 at 19:55
  • Talk about the "keys" (B key, M key, E key) if you know anything about it. For example I'm seeing M.2 cards that have an "E key" and are USB 3.0 or Wifi. – LawrenceC May 31 '17 at 20:03
  • @LawrenceC the adapter has an M-key and the M-key is good for PCIe, SATA and SMBus. – comfreak Jun 02 '17 at 14:02