View source for M.2

{{Short description|Standard for miniature computer expansion cards}}
{{Other uses|M2 (disambiguation){{!}}M2}}
{{Redir|NGFF|the Next Generation Small Form Factor (aka NF1/M.3)|NGSFF<!-- red link with possibilities -->|the Enterprise and Data Center Standard Form Factor|EDSFF}}
{{Use dmy dates|date=August 2014}}
{{Infobox computer hardware
| name = M.2
| image = [[Image:Intel 512G M2 Solid State Drive.jpg|250px]]
| caption = An M.2 2280 [[solid-state drive]] (SSD), 22 mm wide and 80 mm long
| invent-date =
| invent-name =
| designfirm = [[PCI-SIG]]
| introduced = {{Start date and age|2013|11|01}}
| discontinued =
| conn1 = [[Motherboard]]
| via1_1 = [[PCI Express#PCI Express 3.0|PCIe 3.0]] ×4
| via1_2 = [[PCI Express#PCI Express 4.0|PCIe 4.0]] ×4
| via1_3 = [[PCI Express#PCI Express 5.0|PCIe 5.0]] ×4
| via1_4 = [[Serial ATA&nbsp;3.0]]
| via1_5 = [[USB&nbsp;3.0]]
| via1_6 =
| via1_7 =
| class-name = Speeds
| class1 =
| class2 =
| class3 =
| class4 =
| class5 =
| manuf1 = [[Intel]]
| manuf2 = [[Phison]]
| manuf3 = [[Realtek]]
| manuf4 = [[Samsung]]
| manuf5 = [[Silicon Motion]]
| manuf6 = [[SK Hynix]]
| dimensions = {{ubl|22 mm × 30 mm | 22 mm × 42 mm | 22 mm × 60 mm | 22 mm × 80 mm | 22 mm × 110 mm}}
}}
[[File:M.2 and mSATA SSDs comparison.jpg|thumb|250px|A size comparison of an mSATA SSD (left) and an M.2 2242 SSD (right)]]
'''M.2''', pronounced ''m dot two''<ref>{{cite web |last=Gillis |first=Alexander S. |date=July 2021 |title=Definition: M.2 SSD |url=https://www.techtarget.com/searchstorage/definition/M2-SSD |website=TechTarget |language=en-US |access-date=February 24, 2022}}</ref> and formerly known as the '''Next Generation Form Factor''' ('''NGFF'''), is a specification for internally mounted computer [[expansion card]]s and associated connectors. M.2 replaces the Mini SATA ([[mSATA]]) standard and the Mini PCIe ([[mPCIe]]) standard (which is how it got the short name of M dot 2 from being Mini SATA 2). Employing a more flexible physical specification, M.2 allows different module widths and lengths, which, paired with the availability of more advanced [[Interface (computing)|interfacing]] features, makes M.2 more suitable than mSATA in general for [[solid-state storage]] applications, particularly in smaller devices such as [[ultrabook]]s and [[Tablet computer|tablets]].<ref name="snia-webcast">{{cite web |last1=Handy |first1=Jim |last2=Tanguy |first2=Jon |last3=May |first3=Jaren |last4=Akerson |first4=David |last5=Kim |first5=Eden |last6=Coughlin |first6=Tom |date=September 20, 2014 |title=SNIA Webcast: All About M.2 SSDs |url=http://snia.org/sites/default/files/SSSI%20M%202%20Webcast%20Slides%20v10fnl.pdf |website=[[Storage Networking Industry Association|SNIA]] |language=en-US |access-date=July 15, 2015}}</ref><ref name="sata-io-m.2">{{cite web |title=SATA M.2 Card |url=https://www.sata-io.org/sata-m2-card |website=[[SATA-IO]] |access-date=September 14, 2013}}</ref><ref name="compreviews">{{cite web |last=Kyrnin |first=Mark |title=What Is M.2? New Interface and Form Factor For Compact SSD Drives in Laptops and Desktops |url=http://compreviews.about.com/od/storage/fl/What-Is-M2.htm |website=compreviews.about.com |language=en-US |access-date=July 15, 2015 |archive-date=15 July 2015 |archive-url=https://web.archive.org/web/20150715163843/http://compreviews.about.com/od/storage/fl/What-Is-M2.htm |url-status=dead }}</ref>
[[Bus (computing)|Computer bus]] interfaces provided through the M.2 connector are PCI Express x4 (up to four [[PCI Express lane|lanes]]), [[Serial ATA&nbsp;3.0]], and [[USB&nbsp;3.0]] (a single logical port for each of the latter two).  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.  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.<ref name="snia-webcast" /><ref name="sata-io-m.2" /><ref name="m.2-intro-orvem">{{cite web |title=M.2 Connector (NGFF) Introduction |url=http://www.orvem.eu/attachments/article/130/M%202%20introduction.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140203000954/http://www.orvem.eu/attachments/article/130/M%202%20introduction.pdf |archive-date=February 3, 2014 |website=ATTEND  |access-date=January 17, 2014}}</ref>
The M.2 specification supports [[NVM Express]] (NVMe) as the logical device interface for M.2 PCI Express [[Solid-state drive|SSDs]], in addition to supporting legacy [[Advanced Host Controller Interface]] (AHCI) at the logical interface level.  While the support for AHCI ensures software-level [[backward compatibility]] with [[Legacy system|legacy]] SATA devices and legacy [[operating system]]s, NVM Express is designed to fully utilize the capability of high-speed PCI Express storage devices to perform many [[I/O]] operations [[Parallelism (computing)|in parallel]].<ref name="snia-webcast" />{{rp|14}}<ref name="ahci-nvme">{{cite web |last=Landsman |first=Dave |date=August 9, 2013 |title=AHCI and NVMe as Interfaces for SATA Express Devices – Overview |url=https://www.sata-io.org/sites/default/files/documents/NVMe%20and%20AHCI%20as%20SATA%20Express%20Interface%20Options%20-%20Whitepaper_.pdf |website=[[SATA-IO]] |language=en-US |access-date=July 15, 2015}}</ref>
== Features ==
[[File:SATA Express interface.svg|thumb|upright=1.8|A high-level overview of the [[SATA Express]] software architecture, which also applies to M.2.<ref name="snia-webcast" />{{rp|14}}  It supports both legacy SATA and PCI Express storage devices, with [[AHCI]] and [[NVMe]] as the logical device interfaces.<ref name="ahci-nvme" />{{rp|4}}]]
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 drive]]s (SSDs).<ref>{{cite web |title=SATA-IO FAQ: What is the M.2 card and what is the status of the specification? |url=https://www.sata-io.org/sites/default/files/images/SATA-IO%20FAQ%20-%20071813a%20%283%29.pdf#page=2 |website=[[SATA-IO]] |date=August 8, 2013 |access-date=July 15, 2015 |format=PDF |page=2}}</ref>  The [[SATA 3.2|SATA revision 3.2]] specification, in its gold revision {{As of|2013|8|lc=yes}}, standardizes M.2 as a new format for storage devices and specifies its hardware layout.<ref name="snia-webcast" />{{rp|12}}<ref>{{cite web |title=Serial ATA Revision 3.2 (Gold Revision) |url=http://www.knowledgetek.com/graphicsNew/SerialATA_Revision_3_2_Gold%28with%20Links%29.pdf#page=194 |archive-url=https://web.archive.org/web/20140327221409/http://www.knowledgetek.com/graphicsNew/SerialATA_Revision_3_2_Gold%28with%20Links%29.pdf |archive-date=March 27, 2014 |format=PDF |pages=194–209 |website=KnowledgeTek |publisher=[[SATA-IO]] |date=August 7, 2013 |access-date=July 15, 2015}}</ref> [[Bus (computing)|Buses]] exposed through the M.2 connector include [[PCI Express]] (PCIe)&nbsp;3.0 and newer, [[Serial ATA]] (SATA)&nbsp;3.0 and [[USB]]&nbsp;3.0; all these standards are [[backward compatible]].
The M.2 specification provides up to four [[PCI Express lane]]s and one logical [[SATA&nbsp;3.0]] (6&nbsp;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.  Exposed PCI Express lanes provide a pure PCI Express connection between the host and storage device, with no additional layers of [[Bus (computing)|bus]] abstraction.<ref name="pcie-storage">{{cite web |last=Wassenberg |first=Paul |date=June 19, 2013 |title=SATA Express: PCIe Client Storage |url=https://www.sata-io.org/sites/default/files/documents/SATA_Express-SV2013.pdf |publisher=[[SATA-IO]] |access-date=October 2, 2013}}</ref> [[PCI-SIG]] M.2 specification, in its revision 1.0 {{As of|2013|12|lc=yes}}, provides detailed M.2 specifications.<ref name="snia-webcast" />{{rp|12}}<ref name="m.2_specification">{{cite web |title=PCI Express M.2 Specification Revision 1.0 |url=http://www.pcisig.com/specifications/pciexpress/M.2_Specification/ |website=[[PCI-SIG]] |year=2013 |access-date=December 14, 2013}}</ref>
=== Storage interfaces ===
Three options are available for the logical device interfaces and command sets used for interfacing with M.2 storage devices, which may be used depending on the type of M.2 storage device and available [[operating system]] support:<ref name="snia-webcast" />{{rp|14}}<ref name="ahci-nvme" /><ref name="pcie-storage" />
; Legacy SATA: Used for SATA SSDs, and interfaced through the AHCI driver and [[Legacy system|legacy]] SATA&nbsp;3.0 (6&nbsp;Gbit/s) port exposed through the M.2 connector.
; PCI Express using AHCI: Used for PCI Express SSDs and interfaced through the [[AHCI]] driver and provided PCI Express lanes, providing [[backward compatibility]] with widespread SATA support in operating systems at the cost of lower performance.  AHCI was developed when the purpose of a [[host bus adapter]] (HBA) in a system was to connect the CPU/memory subsystem with a much slower storage subsystem based on rotating [[Magnetic storage|magnetic media]]; as a result, AHCI has some inherent [[NVMe vs AHCI|inefficiencies]] when applied to SSD devices, which behave much more like [[Random-access memory|RAM]] than like spinning media.
; PCI Express using NVMe: Used for PCI Express SSDs and interfaced through the [[NVMe]] driver and provided PCI Express lanes, as a high-performance and scalable host controller interface designed and optimized especially for interfacing with PCI Express SSDs.  NVMe has been designed from the ground up, capitalizing on the low [[Latency (engineering)|latency]] and enhanced [[Parallelism (computing)|parallelism]] of PCI Express SSDs, and complementing the [[Parallelism (computing)|parallelism]] of contemporary [[Central processing unit|CPUs]], platforms and applications. At a high level, primary [[NVMe vs AHCI|advantages of NVMe over AHCI]] relate to NVMe's ability to exploit parallelism in host hardware and software, based on its design advantages that include data transfers with fewer stages, greater depth of [[command queue]]s, and more efficient [[interrupt]] processing.
== {{Anchor|FORM-FACTORS|KEYING}}Form factors and keying ==
[[File:M2 Edge Connector Keying.svg|thumb|upright=1.6|right|M.2 keying notches in B and M positions; the offsetting of the pins on different sides of an M.2 module is also visible.<ref name="rog-asus-313352014" />]]
[[File:M.2 2230 M-key SSD in comparison with Micro-SD card.jpg|thumb|right|upright=1.6|An M.2 2230 SSD, 22&nbsp;mm wide and 30&nbsp;mm long, with the key in the M position, and with a microSD card on top for scale.  The large chip on the M.2 module is a single-chip SSD conforming to the M.2 1620 [[ball grid array]] (BGA) form factor.]]
[[File:SSD size variations.jpg|thumb|right|Size examples of M.2 SSDs. The first two digits of the size number are the width and the remaining digits the length in millimeters; a 2242-sized M.2 SSD is 22mm x 42mm. M.2 slots on motherboards and other devices may not support all SSD sizes.<ref>{{cite web |title=Which SSD is Compatible with PS5? |date=29 March 2023 |url=https://gamingconsole101.com/ps5/which-ssd-is-compatible-with-ps5/ |publisher=Gaming Console 101 |access-date=2 April 2023}}</ref>]]
The M.2 standard is based on the [[mSATA]] standard, which uses the existing [[PCI Express Mini Card]] (Mini PCIe) [[Form factor (design)|form factor]] and connector.  M.2 adds the possibility of larger [[printed circuit board]]s (PCBs), allowing longer modules and double-sided component population.  Consequently, M.2 [[SSD]] modules can provide double the storage capacity within the footprint of an mSATA device.<ref name="snia-webcast" />{{rp|20,22–23}}<ref name="compreviews" /><ref>{{cite web |title=M.2 Frequently Asked Questions |url=http://www.kingston.com/en/ssd/s/m2_faq |website=Kingston Technology |language=en-US |access-date=July 15, 2015}}</ref>
M.2 modules are rectangular, with an [[edge connector]] on one side and a semicircular mounting hole at the center of the opposite edge.  The edge connector has 75 positions with up to 67 pins, employing a 0.5&nbsp;mm [[Pin pitch|pitch]] and offsetting the pins on opposing sides of the PCB from each other.  Each pin on the connector is rated for up to 50&nbsp;[[volt|V]] and 0.5&nbsp;[[ampere|A]], while the connector itself is specified to endure 60 mating cycles.<ref name="te-ngff" />{{rp|6}} However, many M.2 slots (Socket 1, 2 and 3) found on motherboards only provide up to 3.3 [[volt|V]] power.<ref>https://media.digikey.com/pdf/Data%20Sheets/Viking%20PDFs/PSFNP5xxxx5xxx_C.pdf {{Bare URL PDF|date=August 2024}}</ref><ref>https://www.nxp.com/docs/en/application-note/AN13049.pdf {{Bare URL PDF|date=August 2024}}</ref><ref>https://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/ssd-530-m2-specification.pdf {{Bare URL PDF|date=August 2024}}</ref>
The M.2 standard allows module widths of 12, 16, 22 and 30&nbsp;mm, and lengths of 16, 26, 30, 38, 42, 60, 80 and 110&nbsp;mm.  Initial line-up of the commercially available M.2 expansion cards is 22&nbsp;mm wide, with varying lengths of 30, 42, 60, 80 and 110&nbsp;mm.<ref name="sata-io-m.2" /><ref name="m.2-intro-orvem" /><ref name="te-ngff" /><ref>{{cite web |last=Mujtaba |first=Hassan |date=July 2, 2013 |title=Intel SSD 530 Series Arriving Next Week – Feature NGFF M.2 Interface |url=http://wccftech.com/intel-ssd-530-series-arriving-august-2013-feature-ngff-m2-interface/ |website=Wccftech |language=en-US |access-date=September 14, 2013}}</ref> The codes for the M.2 module sizes contain both the width and length of a particular module; for example, "2242" as a module code means that the module is 22&nbsp;mm wide and 42&nbsp;mm long, while "2280" denotes a module 22&nbsp;mm wide and 80&nbsp;mm long.
An M.2 module is installed into a mating connector provided by the host's circuit board, and a single mounting screw secures the module into place.  Components may be mounted on either side of the module, with the actual module type limiting how thick the components can be; the maximum allowable thickness of components is 1.5&nbsp;mm per side, and the thickness of the PCB is {{nowrap|0.8 mm ± 10%}}.<ref name="m.2_specification" />  Different host-side connectors are used for single- and double-sided M.2 modules, providing different amounts of space between the M.2 expansion card and the host's PCB.<ref name="compreviews" /><ref name="m.2-intro-orvem" /><ref name="te-ngff" />  Circuit boards on the hosts are usually designed to accept multiple lengths of M.2 modules, which means that the sockets capable of accepting longer M.2 modules usually also accept shorter ones by providing different positions for the mounting screw.<ref>{{cite web |title=M2P4S M.2 (NGFF) PCIe base SSD to PCIe ×4 Adapter |url=http://www.hwtools.net/Adapter/M2P4S.html |website=HW Tools |language=en-US |date=February 14, 2014 |access-date=June 22, 2014}}</ref><ref>{{cite web |last=Burek |first=John |date=April 14, 2015 |title=2015 Guide: The Best M.2 Solid-State Drives |url=http://www.computershopper.com/feature/2015-guide-the-best-m.2-solid-state-drives |website=Computer Shopper |language=en-US |access-date=July 15, 2015 |archive-date=28 December 2015 |archive-url=https://web.archive.org/web/20151228055155/http://www.computershopper.com/feature/2015-guide-the-best-m.2-solid-state-drives |url-status=dead }}</ref>
{| class="wikitable" style="margin-left: 0.5em; margin-right: 2em; margin-top: 0.75em; margin-bottom: 0.9em;"
|+ M.2 module keying and provided interfaces<ref name="m.2-intro-orvem" />{{rp|8}}<ref name="te-ngff">{{cite web |title=M.2 (NGFF) Quick Reference Guide |url=http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1-1773702-1NGFFQRG-EN&DocType=DS&DocLang=EN |format=PDF |website=Tyco Electronics |access-date=November 16, 2013}}</ref>{{rp|3}}<ref>{{cite web |title=SMBus interface for SSD Socket&nbsp;2 and Socket&nbsp;3 (PCI-SIG engineering change notice) |url=https://pcisig.com/sites/default/files/specification_documents/4_SMBus_interface_for_SSD_Socket_2_and_Socket_3.pdf#page=5 |format=PDF |page=2 |website=[[PCI-SIG]] |date=August 11, 2014 |access-date=August 5, 2015 |archive-url=https://web.archive.org/web/20150714093722/http://pcisig.com/sites/default/files/specification_documents/4_SMBus_interface_for_SSD_Socket_2_and_Socket_3.pdf#page=5 |archive-date=July 14, 2015 |url-status=dead}}</ref><ref>{{Cite web |title=How to distinguish the differences between M.2 cards |url=https://www.dell.com/support/article/en-us/sln301626/how-to-distinguish-the-differences-between-m-2-cards?lang=en |website=Dell |language=en-US |access-date=March 24, 2020}}</ref><ref name="pcisig 2013-11">{{cite web |title=PCI Express M.2 Specification, Revision 1.0 |url=http://read.pudn.com/downloads794/doc/project/3133918/PCIe_M.2_Electromechanical_Spec_Rev1.0_Final_11012013_RS_Clean.pdf#page=23 |archive-url=https://web.archive.org/web/20210118201723/http://read.pudn.com/downloads794/doc/project/3133918/PCIe_M.2_Electromechanical_Spec_Rev1.0_Final_11012013_RS_Clean.pdf#page=23 |archive-date=January 18, 2021 |format=PDF |page=23 |website=[[Peripheral Component Interconnect#Special Interest Group|PCI-SIG]] |date=November 1, 2013 |access-date=June 13, 2020}}</ref>
|-
! Key<br />ID
! Notched<br />pins
! style="min-width: 27em;" | Provided interfaces
! Dimensions
! Uses
|-
| style="text-align: center;" | A (Socket 1)
| style="text-align: center;" | 8–15
|2 of [[PCIe]]&nbsp;×1, USB&nbsp;2.0, [[I2C|I<sup>2</sup>C]] and [[DisplayPort|DP]]&nbsp;×4
| 1630, 2230, 3030
| [[Wi-Fi]], [[WWAN]], [[GPS receiver|GPS]], [[Bluetooth]], [[Near-field communication|NFC]]
|-
| style="text-align: center;" | B (Socket 2)
| style="text-align: center;" | 12–19
|[[SATA]], PCIe&nbsp;×2, USB&nbsp;2.0 and 3.0, audio, [[User identity module|UIM]], [[HSIC]], [[SSIC]], I<sup>2</sup>C and [[SMBus]]
| 2230, 2242, 2260, 2280, 22110
| [[SSD]]
|-
| style="text-align: center;" | C
| style="text-align: center;" | 16–23
| rowspan="2" colspan="3" | Reserved for future use
|-
| style="text-align: center;" | D
| style="text-align: center;" | 20–27
|-
| style="text-align: center;" | E (Socket 1)
| style="text-align: center;" | 24–31
| 2 of PCIe&nbsp;×1, USB&nbsp;2.0, [[I2C|I<sup>2</sup>C]], [[Secure Digital Input Output|SDIO]], [[UART]], [[PCM]] and [[CNVi]]
| 1630, 2230, 3030
| [[Wi-Fi]], [[WWAN]], [[GPS receiver|GPS]], [[Bluetooth]], [[Near-field communication|NFC]]
|-
| style="text-align: center;" | A+E (Socket 1)
| style="text-align: center;" | 8–15 and 24–31
| 2 of PCIe&nbsp;×1, USB&nbsp;2.0 and [[CNVi]]
| 1630, 2230, 3030
|  [[Wi-Fi]], [[WWAN]], [[GPS receiver|GPS]], [[Bluetooth]], [[Near-field communication|NFC]]
|-
| style="text-align: center;" | F
| style="text-align: center;" | 28–35
| colspan="3" | Future Memory Interface (FMI)
|-
| style="text-align: center;" | G
| style="text-align: center;" | 39–46
| colspan="3" | Reserved for custom use (unused in the M.2 specification)
|-
| style="text-align: center;" | H
| style="text-align: center;" | 43–50
| rowspan="4" colspan="3" | Reserved for future use
|-
| style="text-align: center;" | J
| style="text-align: center;" | 47–54
|-
| style="text-align: center;" | K
| style="text-align: center;" | 51–58
|-
| style="text-align: center;" | L
| style="text-align: center;" | 55–62
|-
| style="text-align: center;" | M (Socket 3)
| style="text-align: center;" | 59–66
| SATA, PCIe&nbsp;×4, and SMBus
| 2230, 2242, 2260, 2280, 22110
| [[SSD]]
|-
| style="text-align: center;" | B+M (Socket 2)
| style="text-align: center;" | 12-19 and 59–66
| SATA, PCIe&nbsp;×2, and SMBus
| 2230, 2242, 2260, 2280, 22110
| [[SSD]]
|}
{| class="wikitable" style="text-align: center; margin-left: 0em; margin-right: 0.5em; margin-top: 0.75em; margin-bottom: 0.9em;"
|+ Maximum component thickness on M.2 modules<ref name="m.2-intro-orvem" />{{rp|8}}<ref name="te-ngff" />{{rp|3}}
|-
! Type<br />ID
! Top <br />side
! Bottom <br />side
|-
| S1 || 1.20&nbsp;mm ||&mdash;
|-
| S2 || 1.35&nbsp;mm ||&mdash;
|-
| S3 || 1.50&nbsp;mm ||&mdash;
|-
| D1 || 1.20&nbsp;mm || 1.35&nbsp;mm
|-
| D2 || 1.35&nbsp;mm || 1.35&nbsp;mm
|-
| D3 || 1.50&nbsp;mm || 1.35&nbsp;mm
|-
| D4 || 1.50&nbsp;mm || 0.70&nbsp;mm
|-
| D5 || 1.50&nbsp;mm || 1.50&nbsp;mm
|}
[[File:M.2 connector on a computer motherboard.jpg|thumb|right|upright=1.6|An M.2 socket on a [[motherboard]], visible in the upper-left portion of the picture.  The socket is keyed in the M position and provides two positions for the mounting screw, accepting 2260 and 2280 sizes of M.2 modules.]]
The PCB of an M.2 module provides a 75-position edge connector; depending on the type of module, certain pin positions are removed to present one or more keying notches.  Host-side M.2 connectors (sockets) may populate one or more mating key positions, determining the type of modules accepted by the host; {{As of|2014|04|lc=yes}}, host-side connectors are available with only one mating key position populated (either B or M).<ref name="m.2-intro-orvem" /><ref name="te-ngff" /><ref name="rog-asus-313352014">{{cite web |author=Marshall R. |date=April 7, 2014 |title=Buying an M.2 SSD? How to tell which is which? |url=http://rog.asus.com/313352014/labels/guides/buying-an-m-2-ssd-how-to-tell-which-is-which/ |url-status=dead |archive-url=https://web.archive.org/web/20140427211710/http://rog.asus.com/313352014/labels/guides/buying-an-m-2-ssd-how-to-tell-which-is-which/ |archive-date=April 27, 2014 |website=Republic of Gamers |publisher=ASUS |language=en-US |access-date=April 28, 2014}}</ref>  Furthermore, M.2 sockets keyed for SATA or two PCI Express lanes (PCIe&nbsp;×2) are referred to as "socket&nbsp;2 configuration" or "socket&nbsp;2", while the sockets keyed for four PCI Express lanes (PCIe&nbsp;×4) are referred to as "socket&nbsp;3 configuration" or "socket&nbsp;3".<ref name="snia-webcast" />{{rp|15}}<ref>{{cite web |last1=Zhang |first1=Jack |last2=Liang |first2=Mark |title=NVM Express Based Solid-State Drives: Crossing the Chasm, Going Mainstream |url=https://intel.lanyonevents.com/sz15/connect/fileDownload/session/9D9F891F2BE30DC4C945F5F5B197F307/SZ15_SSDS001_102_ENGf.pdf |website=Intel |language=en-US |page=39 |date=July 4, 2015 |access-date=August 27, 2015 |archive-date=5 June 2016 |archive-url=https://web.archive.org/web/20160605094938/https://intel.lanyonevents.com/sz15/connect/fileDownload/session/9D9F891F2BE30DC4C945F5F5B197F307/SZ15_SSDS001_102_ENGf.pdf |url-status=dead }}</ref>
For example, M.2 modules with two notches in B and M positions use up to two PCI Express lanes and provide broader compatibility at the same time, while the M.2 modules with only one notch in the M position use up to four PCI Express lanes; both examples may also provide SATA storage devices.  Similar keying applies to M.2 modules that utilize provided USB&nbsp;3.0 connectivity.<ref name="m.2-intro-orvem" /><ref name="rog-asus-313352014" /><ref>{{cite web |last=Tokar |first=Les |date=November 24, 2013 |title=Understanding M.2 NGFF SSD standardization (or the lack of) |url=http://www.thessdreview.com/daily-news/latest-buzz/understanding-m-2-ngff-ssd-standardization/ |website=The SSD Review |language=en-US |access-date=April 28, 2014}}</ref>
Various types of M.2 modules are denoted using the "WWLL-HH-K-K" or "WWLL-HH-K" naming schemes, in which "WW" and "LL" specify the module width and length in millimeters, respectively.  The "HH" part specifies, in an encoded form, whether a module is single- or double-sided, and the maximum allowed thickness of mounted components; possible values are listed in the right table above.  Module keying is specified by the "K-K" part, in an encoded form using the key IDs from the left table above; it can also be specified as "K" only, if a module has only one keying notch.<ref name="m.2-intro-orvem" /><ref name="te-ngff" />
Beside socketed modules, the M.2 standard also includes the option for having permanently [[Soldering|soldered]] single-sided modules.<ref name="te-ngff" />
{{anchor|M.3|NF1|NGSFF|XFM}}
== Alternative standards ==
=== NGSFF ===
<!-- This should be expanded into a separate article, but parked here to have a target for incoming redirects like [[M.3 (computing)]], [[Samsung NF1]], [[NGSFF]], [[Next Generation Small Form Factor]] -->
In 2017, Samsung introduced a new form factor called ''Next Generation Small Form Factor'' (NGSFF), also known as NF1 or M.3, which may replace [[U.2]] in server applications.<ref>{{cite web |last1=Hensel |first1=Martin |last2=Graefen |first2=Rainer |date=July 27, 2018 |title=Was sind NF1, M.3 und NGSFF? |url=https://www.storage-insider.de/was-sind-nf1-m3-und-ngsff-a-736403/ |work=StorageInsider |publisher=Vogel Communications Group |language=de |access-date=July 10, 2022 |url-status=live |archive-url=https://web.archive.org/web/20220710160435/https://www.storage-insider.de/was-sind-nf1-m3-und-ngsff-a-736403/ |archive-date=July 10, 2022}}</ref> The NGSFF connector is electrically and dimensionally compatible with M.2 (revision 1.1)'s connector; new functionality is achieved through previously unused (N/C) pins.<ref name="DWang">{{cite web |last1=Wang |first1=David |title=Next Generation Small Form Factor (NGSFF) SSD Proposal |url=https://files.futurememorystorage.com/proceedings/2017/20170810_FC32_Wang.pdf}}</ref> The main changes compared to M.2 are:
* The width (or "height") of the SSD is increased from 22 mm to 30.5 mm; the thickness is increased from 3.88 mm to 4.38 mm. These changes allow more NAND chips to be fitted onto an SSD while still fitting inside a [[rack unit]].<ref name="Samsung">{{cite web |title=NF1 SSD &#124; Samsung Semiconductor |url=https://www.samsung.com/semiconductor/ssd/nf1-ssd/ |website=Samsung |url-status=dead |archive-url=https://web.archive.org/web/20201002081759/https://www.samsung.com/semiconductor/ssd/nf1-ssd/ |archive-date=October 2, 2020}}</ref>
* New pins for 12 V power. Devices are supposed to mainly use 12 V power instead of the old 3.3 V, which has been made optional.<ref name="Samsung"/>
* Ability to run two PCIe ports (each with two lanes) on one NGSFF port.<ref name="DWang"/>
* Features for rackmount servers: hotswap support, indicator LEDs, SSD tray (with new screw holes).<ref name="DWang"/>
In 2018, the PCI-SIG issued a warning that NGSFF's new pin usage clashes with the pin usage in the upcoming 1.2 revision of the M.2 standard. The new revision uses some of the previously non-connected (N/C) pins to deliver 1.8 V power and USB 2.0 data on the "M" socket. Samsung has sought to standardize its NGSFF/NF1 through [[JEDEC]], but the process appears to have stalled.<ref>{{cite web |last1=Tallis |first1=Billy |title=PCI-SIG Warns Of Incompatibilities Between M.2 And Samsung's NGSFF/NF1 |url=https://www.anandtech.com/show/13609/pcisig-warns-of-incompatibilities-between-m2-and-samsungs-ngsff |website=www.anandtech.com}}</ref>
=== XFM ===
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JEDEC JESD233 is another specification called ''Crossover Flash Memory'' (XFM) for XFM Embedded and Removable Memory Devices (XFMD). It targets to replace the M.2 form factor with a significantly smaller one (also called XT2), so that it can also be designed as an alternative to soldered memory. XFM Express utilizes a [[NVM Express|NVMe]] logical interface over a [[PCI Express]] physical interface.<ref name="Lee_2021">{{cite web |last=Lee |first=Matthew |date=August 28, 2021 |title=Move over M.2, here comes the XFM memory specification - And it might displace soldered storage, too, with some luck |url=https://www.techspot.com/news/91000-move-over-m2-here-comes-xfm-memory-specification.html |work=TechSpot |language=en-US |access-date=July 10, 2022 |url-status=live |archive-url=https://web.archive.org/web/20220710164145/https://www.techspot.com/news/91000-move-over-m2-here-comes-xfm-memory-specification.html |archive-date=July 10, 2022}}</ref><ref name="Liu_2019">{{cite web |last=Liu |first=Zhiye |date=August 6, 2019 |title=Toshiba Unveils XFMEXPRESS Form Factor for NVMe SSDs |url=https://www.tomshardware.com/news/toshiba-xfmexpress-nvme-ssd,40104.html |website=Tom's Hardware |language=en-US |access-date=July 10, 2022}}</ref>
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== Gallery ==
<gallery widths="200px" heights="160px">
M.2 2242 SSD connected into USB 3.0 adapter.jpg|An M.2 2242 SSD connected into a [[USB]]&nbsp;3.0 adapter and connected to a computer
Delock USB m.2 NVMe docking station-oblique FS PNr°0912.jpg|A docking station for M.2 modules
Delock USB m.2 NVMe docking station-slot FS PNr°0914.jpg|The connection slot of the docking station
Samsung 980 PRO PCIe 4.0 NVMe SSD 1TB-top PNr°0915.jpg|A Samsung 980 PRO PCIe 4.0 NVMe SSD with 1&nbsp;TB of storage capacity
M.2 1630 and M.2 2230 WiFi cards side by side.jpg|M.2 2230 (left) and M.2 1630 [[WiFi]] cards
</gallery>
== See also ==
{{Portal|Electronics}}
* [[Enterprise and Data Center Standard Form Factor]] (EDSFF)
* [[List of interface bit rates]]
* [[NVM Express]] (NVMe)
* {{Section link|Solid-state drive#Configurations}}
* [[U.2]]
== References ==
{{Reflist|30em}}
== External links ==
{{Commons category|M.2}}
* {{Official website|https://www.sata-io.org|Serial ATA International Organization}} (SATA-IO) official website
* {{Official website|https://www.pcisig.com|Peripheral Component Interconnect Special Interest Group}} (PCI-SIG) official website
* [https://arstechnica.com/gadgets/2015/02/understanding-m-2-the-interface-that-will-speed-up-your-next-ssd Understanding M.2, the interface that will speed up your next SSD], ''[[Ars Technica]]'', February 9, 2015, by Andrew Cunningham
* [https://lwn.net/Articles/547903 LFCS: Preparing Linux for nonvolatile memory devices], [[LWN.net]], April 19, 2013, by Jonathan Corbet
* [https://web.archive.org/web/20140202110152/http://www.snia.org/sites/default/files/SNIASSSIPCIe101WhitePaper1.12013.pdf PCIe SSD 101: An Overview of Standards, Markets and Performance], [[Storage Networking Industry Association|SNIA]], August 2013, archived from the original on February 2, 2014
* [https://www.congatec.com/fileadmin/user_upload/Documents/Application_Notes/AN43_M.2_Pinout_Descriptions_and_Reference_Designs.pdf M.2 Pinout Descriptions and Reference Designs], January 28, 2020, an application note from [[:de:Congatec|Congatec]]
* {{US patent|20130294023|Interface card mount}}{{snd}} US patent 20130294023, November 7, 2013, assigned to Raphael Gay
{{Solid-state drive}}
[[Category:M.2| ]]
[[Category:Computer-related introductions in 2013]]
[[Category:Computer connectors]]
[[Category:Motherboard expansion slot]]
[[Category:Peripheral Component Interconnect]]
[[Category:SATA Express]]
[[Category:Serial ATA]]
[[Category:USB]]