For my current project I am adding an M.2 slot for additional storage. Even though SATA data throughput is more than sufficient I would like to support both SATA and PCIe based SSDs, as I dont know what will be more/less available and affordable in future.
The M.2 connectors use keying notches in different positions, depending on the provided interfaces. Each key position is identified by a letter.
- Key B: SATA + PCIe x2 (+ others)
- Key M: SATA + PCIe x4
A quick search for M.2 SSDs on amazon showed that most NVMe/PCIe based SSDs use Key M, while SATA SSDs use a combined Key B and M. Therefore, for maximum compatibility, I need to use Key M.
Available System Interfaces
My system has one SATA and 2 PCIe lanes that may be connected to the M.2 receptacle, what is the requirement for Key B. I am missing 2 PCIe lanes for key M.
I plan to use the M key for maximum mechanical compatibility and would like to provide one SATA and 2 PCIe-Lanes on the M.2 connector.
- Do all NVMe/PCIe based SSDs work with 2 instead of 4 PCIe lanes?
- Is there a requirement on which PCIe lanes need to be used in this case?
- How may the two PCIe lanes that are not used be terminated?