Differences Between M2 Cards M2 Slots Keys Sizes and Types (2024)

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 differencesbetween M.2 SSDs?
5. How to confirm which M.2 supports which key connectors

Description of cards

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. (for example: To suit the individual needs of the computer and provide an array of configuration options for the user.) 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 is 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, and bus (dual slot cards use two letters)

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

In the image above, the first four digits are defined as:

• TheWi-Fi module (a) is 16 mm wide and 30 mm long, so it is labeled as 1630
• The SSD (b) is 22 mm wide and 42 mm long, so it is labeled as 2242
• The two larger SSDs (C and D) are 22 mm wide and 80 mm long, so they are labeled as 2280

This chart describes the key interfaces as they relate to the physical sizes of M.2 cards and their common uses (Table 1 [English only]):

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:

Back to top

M.2 Slot on Motherboard

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

Back to top

Two types of M.2 SSD (SATA and PCI-E)

1. SSDs using the SATA bus tend to use B-keys
2. SSDs using the PCIe x2 bus can use both B-keys and M-keys (to maximize compatibility

Note: SSDs using the PCIe x4 bus (fast SSDs) use M-keys since it is 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:
   

Back to top

What are the performance differencesbetween M.2 SSDs?

In general:

• M.2 SSDs using the SATA bus are similar in performance to SSDs using a SATA connector, but are smaller
• M.2 SSDs using the PCIe bus are faster than M.2 SSDs using a SATA bus
• M.2 M-key SSDs using the PCIe bus are faster than M.2 B-key SSDs 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 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.

Back to top

How to confirm which M.2 supports which key connectors

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

Back to top

Recommended Articles

Here are some recommended articles related to this topic that might be of interest to you.

• Understanding and Troubleshooting the Hard Disk Drive (HDD) or Solid-State Drive (HDD or SSD) on a Dell Computer
• M.2 NVMe Device Specifications and Upgrade Requirements for Precision, OptiPlex, Latitude, and XPS Systems