On my Dell Optiplex tower PC it has a spare M.2 slot on the motherboard for a small SSD and I need to install an additional hard drive.

I already have a SATA drive but the only slot free is the M.2 slot, the other two SATA are used

On the motherboard it has written M.2/SATA near the port so I assume an adaptor exists to a normal SATA connector?

I have tried searching for M.2 to SATA but it only brings up a SATA -> M.2 adaptor which is the wrong way round! Is there a reverse of this or do they not exist?

I want to install it internally as I have used all my USB ports

  • It says M.2/SATA because it uses the SATA interface, which is important to know when purchasing an M.2 drive. You may here NVMe mentioned when talking about M.2 drives, which take advantage of PCIe lanes to allow for significantly faster read and write speeds. The M.2 drives that you are able to install are not NVMe and will have their speed restricted by the connection, which is something that you do not mind, but is worth noting because a "SATA to M.2" adapter is not specific enough to find what you need.
    – Kraigolas
    Jul 14, 2020 at 20:16
  • There's even a tiny SATA controller.
    – Daniel B
    Jul 14, 2020 at 20:28

1 Answer 1


Had a similar idea to expand the number of SATA Ports and bought DeLock 62876 Adapter. Unfortunately it is a Key B adapter that does not fit in Key M slots. I could solve it by "adding" the needed key (the 4 black marked pins) and connecting the 4th pin (PEDET) with 3rd (GND). This will signal host controller that we want SATA mode. (Not sure why this was not done by DeLock already, seems to be already required in Key B mode as well..)

M.2 adapter mod

It works and I finally have a Mini-ITX board with more then 4 SATA (Asus B550-I, tested with 5 SATA disks, 6 should work too).

But make sure the M.2 SATA mode of your board works additionally to existing SATA ports and does not replace one of them (see board manual).

There is also a good reference of pinout for B and M Key M.2 slots here: https://www.congatec.com/fileadmin/user_upload/Documents/Application_Notes/AN43_M.2_Pinout_Descriptions_and_Reference_Designs.pdf

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