Exposed PCI Express lanes provide a pure PCI Express connection between the host and storage device, with no additional layers of bus abstraction. The M.2 specification provides up to four PCI Express lanes and one logical SATA 3.0 (6 Gbit/s) port, and exposes them through the same connector so both PCI Express and SATA storage devices may exist in the form of M.2 modules. : 12 Buses exposed through the M.2 connector include PCI Express 3.0 and newer, Serial ATA (SATA) 3.0 and USB 3.0 all these standards are backward compatible. The SATA revision 3.2 specification, in its gold revision as of August 2013, standardizes the M.2 as a new format for storage devices and specifies its hardware layout. M.2 modules can integrate multiple functions, including the following device classes: Wi-Fi, Bluetooth, satellite navigation, near field communication (NFC), digital radio, WiGig, wireless WAN (WWAN), and solid-state drives (SSDs). : 14 It supports both legacy SATA and PCI Express storage devices, with AHCI and NVMe as the logical device interfaces. : 14 Ī high-level overview of the SATA Express software architecture, which also applies to M.2.

While the support for AHCI ensures software-level backward compatibility with legacy SATA devices and legacy operating systems, NVM Express is designed to fully utilize the capability of high-speed PCI Express storage devices to perform many I/O operations in parallel. The M.2 specification supports NVM Express (NVMe) as the logical device interface for M.2 PCI Express SSDs, in addition to supporting legacy Advanced Host Controller Interface (AHCI) at the logical interface level. Different M.2 connector keying notches denote various purposes and capabilities of both the M.2 hosts and modules, and also prevent the M.2 modules from being inserted into incompatible host connectors. It is up to the manufacturer of the M.2 host or module to select which interfaces are to be supported, depending on the desired level of host support and the module type. Ĭomputer bus interfaces provided through the M.2 connector are PCI Express 4.0 (up to four lanes), Serial ATA 3.0, and USB 3.0 (a single logical port for each of the latter two). Employing a more flexible physical specification, the M.2 allows different module widths and lengths, and, paired with the availability of more advanced interfacing features, makes the M.2 more suitable than mSATA in general for solid-state storage applications, particularly in smaller devices such as ultrabooks and tablets.

M.2 replaces the mSATA standard, which uses the PCI Express Mini Card physical card layout and connectors. M.2, formerly known as the Next Generation Form Factor ( NGFF), is a specification for internally mounted computer expansion cards and associated connectors.

A size comparison of an mSATA SSD (left) and an M.2 2242 SSD (right)

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