How to distinguish the differences between M.2 cards


How to distinguish the differences between M.2 cards



This article explains the differences between each M.2 card and how to identify the card size and type.

Table of Contents

  1. Description of cards
  2. M.2 Slot on Motherboard
  3. Two types of M.2 SSD (SATA and PCI-E)
  4. What are the performance differences between M.2 SSD's?
  5. How to confirm which M.2 support which key connectors


1. Description

The M.2 platform is versatile and supports a wide variety of M.2 cards. M.2 cards can be configured with different hardware and functionality within the M.2 platform to suit the individual needs of the system and provide an array of configuration options for the user. While physical size is the easiest observable way to distinguish the difference between cards, the M.2 standard uses a numerical naming convention to identify the specific attributes and functionality of the card.

For example, M.2 cards may include:

  • A combination of Wi-Fi and Bluetooth cards
  • A SanDisk SSD that uses the SATA bus
  • An Intel SSD that also uses the PCIe bus
  • A Samsung SSD that can use up to four PCIe lanes (x4)
The numerical naming convention is used to define the size and functionality of the card, here's how:
  • The first two digits specify the width (in millimeters)
  • The second two (or three) digits specify the length (in millimeters)
  • The last letter is intended to specify the key/interface/bus (dual slot cards will use two letters)


Here are some random examples of various sizes of M.2 cards and their key designations:


In the picture above, the first four digits are defined as:
  • The Wi-Fi module (a) is 16mm wide and 30mm long, so it will be labeled as 1630
  • The SSD (b) is 22mm wide and 42mm long, so it will be labeled as 2242
  • The two larger SSDs (c and d) are 22mm wide and 80mm long, so they will be labeled as 2280

This chart describes the key interfaces as they relate to the physical sizes of M.2 cards and their common uses:



This image contains representations of different sizes and series of M.2 SSD for comparison (the series name corresponds to the first four digits defining the size of the M.2 card):



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2. M.2 slot on Motherboard

All motherboard M.2 slots are 22mm wide, even the ones supporting 30mm wide cards.



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3. Two types of M.2 SSD (SATA and PCIe)

  1. SSD's using the SATA bus tend to use B-keys
  2. SSD's using the PCIe x2 bus can use both B-keys & M-keys (to maximize compatibility)
    • NOTE: SSD's using the PCIe x4 bus (very fast SSD's) use M-keys since it's the only one that supports PCIe x4 lanes

Examples from the Dell website:
  1. An M.2 2280 SATA SSD purchased separately:

  2. Available M.2 NVMe (M-key) options for configuration for a Precision 5510:



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4. What are the performance differences between M.2 SSD's?

In general:
  • M.2 SSD's using the SATA bus are similar in performance to SSD's using a SATA connector, but are smaller
  • M.2 SSD's using the PCIe bus are faster than M.2 SSD's using a SATA bus
  • M.2 M-key SSD's using the PCIe bus are faster than M.2 B-key SSD's using the PCIe bus
In summary: SSD using the SATA bus run at SATA speeds regardless of form factor. The PCIe bus is faster than a SATA bus and an M-key SSD is faster than a B-key SSD.

NOTE: All of these performance indicators are relative to the Bus and Bus interface. There are other factors that determine individual SSD performance that are not addressed here.

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5. How to confirm which units support which key connectors

  • Compare the M.2 card and Motherboard specifications to ensure the parameters match (to ensure that the Motherboard supports the desired M.2 card functionality).
  • The main parameters to consider are:
    • Type (SATA or PCI-e)
    • Physical length
    • Model
    • Key interface
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Article ID: SLN301626

Last Date Modified: 09/14/2019 08:40 AM

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