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What is the meaning of the keys of M.2 SSDs?

Question

What is the meaning of the keys of M.2 SSDs?

 


Answer

Depending on which interfaces are provided by a M.2 connector, a specific form of the connection is used. These so-called keys require M.2 plug-in cards with recesses at certain points, so that only suitable plug-in cards fit into the respective M.2 connectors.

Most currently available M.2 SSDs are Key B + M. They have both recesses and can be plugged into Key-B as well as Key-M connectors.
Buyers need to make sure the connector and module support the same key otherwise the M.2 card will not fit.


M2_Edge_Connector_Keying_800px.pngQuelle: wikimedia.org / NikNaks / CC BY-SA 3.0
M.2 can provide both SATA and PCI Express as an interface:

  • Key B: PCIe ×2, SATA
  • Key M: PCIe ×4, SATA

 

Overview of the maximum speeds of different interfaces

As mentioned above, M.2 can provide both SATA and PCI Express as an interface.
M.2 SSDs connected via PCIe offer a speed advantage.
PCIe 2.0 allows 5 GBit/s per lane, PCIe 3.0 allows 8 GBit/s per lane.

Interface Maximum speed
SATA 3 6 GBit/s
PCIe 2.0 x2 10 GBit/s
PCIe 2.0 x4 20 GBit/s
PCIe 3.0 x2 16 GBit/s
PCIe 3.0 x4 32 GBit/s

 

 

References:

General Technical Knowledge Base: M.2

 

Version History
Revision #
2 of 2
Last update:
‎18.05.2018 08:07
Updated by:
 
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