M.2 (formerly known as Next Generation Form Factor and NGFF ) is a specification of compact computer expansion cards and their connectors. It was created as a replacement for the mSATA and Mini PCI-E format, which used the physical connector and the size of the PCI Express Mini Card modules. The M.2 standard allows for a wider variety of module sizes, both in width and in length. The M.2 format is often used to implement productive solid-state drives (based on flash memory , SSD ), especially when used in compact devices, such as ultrabooks and tablets [1] .
The interfaces output to the M.2 connector are a superset of the SATA Express interface. In fact, M.2 is a more compact implementation of SATA Express (provides support for PCI Express 3.0 and SATA 3.0 buses), complemented by an internal USB 3.0 interface. M.2 boards can have various key cutouts to indicate a specific version of the interface used [1] [2] .
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Features
M.2 expansion cards can provide various functions, for example: Wi-Fi , Bluetooth , satellite navigation , NFC- radio, digital radio , Wireless Gigabit Alliance (WiGig), Wireless WAN (WWAN). Fast and compact solid-state flash drives (SSDs) are often manufactured as M.2 modules. The PCI Express 3.0, Serial ATA 3.0 and USB 3.0 buses (including backward compatibility with USB 2.0) are output to the M.2 connector. The SATA 3.2 specification as of August 2013 defined the “SATA M.2” format for storage media [3] [4] .
As part of M.2, PCI Express 4x (4 lines) and one SATA 3.0 port with a speed of up to 6 Gb / s are implemented, so both PCI Express devices and SATA drives can be implemented in the M.2 form factor. The standard PCI Express is used without any additional layers of abstraction [5] . The PCI-SIG group released the M.2 specification version 1.0 in December 2013 [6] .
Three options for implementing the logical interface and a set of commands are available for M.2 expansion cards, by analogy with the SATA Express standard [5] [7] :
- "Legacy SATA"
- Used for SSDs with SATA interface, AHCI driver and speeds up to 6.0 Gb / s (SATA 3.0)
- SATA Express using AHCI
- Used for SSDs with PCI Express interface and AHCI driver (for compatibility with a large number of operating systems). Due to the use of AHCI, the performance may be slightly lower than optimal (obtained with NVMe), since AHCI was designed to interact with slower drives with slow serial access (for example, HDD ), and not for SSDs with fast random access.
- SATA Express using NVMe
- Used for SSDs with PCI Express interface and high-performance NVMe driver, designed to work with fast flash drives. NVMe was designed with low latency and concurrency in a PCI Express PCI Express SSD. NVMe makes better use of parallelism in the host computer and software, requires fewer stages in data transfer, provides a deeper command queue and more efficient interrupt handling.
Form Factor and Keys
The M.2 standard was developed as an update and improvement of the mSATA format, allowing the use of larger printed circuit boards. If mSATA used the sizes of PCI Express Mini Card modules, then M.2 allowed to increase the use of the card area, for example, in M.2 longer modules and two-way placement of components on the board are possible.
M.2 modules have a rectangular shape, on one side of the card there is a connector (75 positions with 67 pads in increments of 0.5 mm). On the opposite side is a semicircular hole for fixing. Each contact can withstand voltages up to 50 V and current up to 0.5 A. The connector guarantees at least 60 cycles of connection-disconnection. The M.2 standard allows modules with a width of 12, 16, 22 or 30 mm and a length of 16, 26, 30, 38, 42, 60, 80 or 110 mm. Initially, M.2 cards were produced with a width of 22 mm and a length of 30, 42, 60, 80 and 110 mm [1] [2] [8] [9] .
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The printed circuit boards of the M.2 expansion cards at one edge provide a blade connector with 75 positions. Depending on the type of module, key sections were made instead of part of the positions. The M.2 slot on the motherboard may have stubs at some key positions, determining the type of modules and interfaces compatible with it. As of April 2014, the slots were executed with a single plug, either in position B or in position M [2] [8] [10] . For example, an M.2 module with two key cuts B and M can use up to two PCI Express lines and is compatible with a large number of slots, while M.2 cards with a key in position M can use up to 4 PCI Express lines. Both options can also use SATA lines. A similar key system is used for M.2 cards with USB 3.0 interface. [2] [10] [11]
Types of M.2 cards are marked with a code according to the scheme WWLL-HH-KK or WWLL-HH-K , where WW and LL are module dimensions in width and length in millimeters. HH encodes whether the module is single-sided or double-sided, as well as the maximum permissible height (thickness) of components placed on it, for example, “D2”. The KK part denotes key sections; if the module uses only one key, one letter K [2] [8] is used .
The most popular M.2 form factors as of 2016: width 22 mm, length 80 or 60 mm (M.2-2280 and M.2-2260), less often 42 mm. Many early M.2 drives and motherboards used the SATA interface. Some motherboards also implement PCI Express [12] . For SSDs, the most popular keys are B (SATA and PCIe x2) and M (SATA and PCIe x4). To connect expansion cards, for example WiFi, modules of size 1630 and 2230 and keys A or E are used [13] .
In addition to removable expansion cards, the M.2 standard defines the option of modules soldered to the motherboard during its manufacture [8] .
Notes
- ↑ 1 2 3 SATA M.2 Card . SATA-IO . Date of treatment 2013-09-14.mdy . 2019 .
- ↑ 1 2 3 4 5 6 7 M.2 Connector (NGFF) Introduction (PDF). orvem.eu . ATTEND. Date of treatment 2014-01-17.mdy . 2019 . Archived February 3, 2014.
- ↑ Serial ATA Revision 3.2 (Gold Revision) (PDF). knowledgetek.com . SATA-IO ( 2013-08-07.mdy . 2019 ). Date of treatment 2014-03-27.mdy . 2019 . Archived March 27, 2014.
- ↑ SATA-IO FAQ . SATA-IO . Date of treatment 2013-09-14.mdy . 2019 .
- ↑ 1 2 Paul Wassenberg. SATA Express: PCIe Client Storage (PDF). SATA-IO (2013). Date of treatment 2013-10-02.mdy . 2019 .
- ↑ PCI Express M.2 Specification Revision 1.0 . PCI-SIG (2013). Date of treatment 2013-12-14.mdy . 2019 .
- ↑ Dave Landsman. AHCI and NVMe as Interfaces for SATA Express Devices - Overview (PDF). SanDisk Date of treatment 2013-10-02.mdy . 2019 .
- ↑ 1 2 3 4 5 6 M.2 (NGFF) Quick Reference Guide (PDF). Tyco Electronics. Date of treatment 2013-11-16.mdy . 2019 .
- ↑ Intel SSD 530 Series Arriving Next Week - Feature NGFF M.2 Interface . WCCF Tech. Date of treatment 2013-09-14.mdy . 2019 .
- ↑ 1 2 Marshall R. Buying an M.2 SSD? How to tell which is which? . Asus ( 2014-04-07.mdy . 2019 ). Date of treatment 2014-04-28.mdy . 2019 .
- ↑ Les Tokar. Understanding M.2 NGFF SSD standardization (or the lack of) . The SSD Review ( 2013-11-24.mdy . 2019 ). Date of treatment 2014-04-28.mdy . 2019 .
- ↑ John Burek . 2016 Guide: The Best M.2 Solid-State Drives, Tested (Eng.) , Computer Shopper (February 8, 2016). Archived July 31, 2016. Date of treatment August 3, 2016.
- ↑ Understanding M.2, the interface that will speed up your next SSD | Ars technica
Links
- The Serial ATA International Organization (SATA-IO)
- PCIe SSD 101: An Overview of Standards, Markets and Performance , SNIA , August 2013, pp. 6-7
- Samsung XP941 M.2 PCIe SSD Review (512 GB) , September 22, 2013
- LFCS: Preparing Linux for nonvolatile memory devices // LWN.net , April 19, 2013
- Interface card mount US patent 20130294023, November 7, 2013
- MY Blog: M.2 NGFF SSD Compatibility List , October 19, 2016 = Compatibility List for M.2 formats and computer technology / Blog Selection Post, 2016-09-06