M.2 is a form factor for plug-in cards of solid state drives( SSD), which is used as an interface for PCIe and SATA with 6 Gbit/s transfer technology. It is incompatible with the PCIe mini card and with mSATA. M.2 is extremely compact and can be installed in notebooks and other small mobile computers. In terms of design, M.2 is similar to the Next Generation Small Form Factor( NGSFF) design.
Plug-in cards according to the M.2 standard are rectangular. They have a connector strip with one or two recesses on one side, and a semicircular recess for mounting on the other. The cutouts in the connector strip are used for interface coding for SATA, PCIe or USB. In terms of data rates, PCI Express 3.0 (PCIe 3.0 x 4) with four lanes of 8 Gbit/s each achieves a data transfer rate of32 Gbit/s and a data transfer rate of 2.5 GB/s. In contrast, a SATA connection with 6 Gbit/s achieves 600 MB/s.
M.2 modules with solid state drives are available in rectangular designs with different side lengths. The different sizes are indicated by a size code in the type specification. It is a number that results from the width and length of the M.2 board. The PCBs have a width of 16.5 mm, 22 mm and 30 mm and lengths of 30, 42, 60 and 80 mm. The size coding for a 22 mm wide and 60 mm long M.2 plug-in card is then M.2-2260.
In addition to the size coding, there is also a marking of the interface that an M.2 port supports. This marking is called a " key" and is a notch in the header. Only these headers fit into the respective M.2 port. M.2 distinguishes between three keys: Key B, Key M and Key B+M. Key B supports PCIe with two lanes or SATA, whereas Key M supports PCIe with four lanes and SATA.