What is an M.2 Slot? NVMe SSD, Wi-Fi & Bluetooth Dedicated Slot Explained for Custom PCs

The M.2 slot is widely used as a slot for connecting M.2 SSDs (NVMe SSDs), Wi-Fi, and Bluetooth modules.

However, if the types and compatibility of M.2 slots are not understood, there is a risk of purchasing products that cannot be installed or not being able to maximize performance.

This article explains in detail the basic knowledge of M.2 slots, including slot length, key types, and important compatibility points that should not be overlooked.

This article also explains how to choose based on motherboard standards, part names, performance, and compatibility.

≫ Related article: How to Choose a Custom PC Motherboard [Performance / Features / Compatibility]

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About the M.2 Slot

First, let’s look at the basic knowledge of the M.2 slot found on motherboards.

What is an M.2 Slot?

The M.2 slot is an interface mainly for connecting high-speed storage such as NVMe SSDs and other expansion cards.

M.2 was designed as the “Next Generation Form Factor (NGFF)”, as a replacement for the traditional mSATA standard.

The M.2 slot is not a single standard; it supports multiple standards (PCIe, SATA, USB), allowing various parts to be connected.

Especially for storage, using an SSD compatible with NVMe enables very fast data transfer.

Slots for NVMe SSDs, Wi-Fi, and Bluetooth

The M.2 slot is widely used as a slot for connecting NVMe SSDs, Wi-Fi, and Bluetooth modules.

It is especially often used for connecting NVMe SSDs, and thanks to its compact size and high data transfer speed, it outperforms traditional SATA SSDs.

This greatly improves PC boot times and application loading speeds.

≫ Related article: How to Choose Storage (SSD/HDD) for Custom PCs [Performance / Features / Compatibility]

Also, by using the M.2 slot for Wi-Fi and Bluetooth, wireless communication functions can be easily added.

This allows even desktop PCs (custom PCs) to connect wirelessly, making it easier to set up a network environment. Using a Bluetooth mouse or keyboard can also eliminate cables, keeping the desk tidy.

With wired LAN, the cable layout may limit where the PC can be placed in a room, but with wireless, placement is much more flexible.

There are also other ways to add Wi-Fi and Bluetooth besides the M.2 slot, and their advantages are explained as well.

≫ Related article: PC Parts to Add Wi-Fi and Bluetooth to a Custom PC

Replacing the mSATA Slot

The M.2 slot has become widely used as a replacement for the mSATA slot.

mSATA was once popular for storage connections in small devices, but the M.2 slot, as its successor, offers more features and flexible connections.

The M.2 slot supports not only the SATA standard but also PCI Express (PCIe), enabling faster data transfer.

This allows SSD performance to be maximized.

In addition, the compact size and flexible design of the M.2 slot make it suitable for laptops and small devices.

For these reasons, the M.2 slot has become the standard storage connection method on modern motherboards, replacing the mSATA slot.

Comparison of NVMe SSD and SATA SSD

The M.2 slot is mainly used for installing NVMe SSDs, so let’s compare NVMe SSDs and SATA SSDs.

NVMe SSDs are Mainstream

There are three types of storage standards: NVMe SSD, SATA SSD, and (SATA) HDD, but NVMe SSDs are now mainstream.

Depending on the use, SATA SSDs or HDDs may be used as a second or later drive, but at least for the main storage where the OS and apps are installed, NVMe SSD is the only choice.

Let’s look at which storage standards custom PC users are choosing.

Using the Custom PC Tool I developed, which allows users to easily “estimate”, “check compatibility”, and “calculate power consumption” by simply selecting parts, I aggregated the share based on the parts users selected.

M.2 SSD (Type 2280) is an NVMe SSD, and 2.5-inch is a SATA SSD.

Comparing these two, over 90% of users choose NVMe SSDs.

When NVMe SSDs first appeared, they were more expensive than SATA SSDs of the same capacity, but recently there is almost no price difference.

Considering the advantages of data transfer speed and no need for wiring, it is natural that NVMe SSDs have become the center of attention.

In storage configuration data, the main setups are a single NVMe SSD, two NVMe SSDs, or NVMe SSD + HDD.

In any case, NVMe SSDs are used most often.

A lot of other statistical data has also been summarized, so please refer to it.

≫ Related article: Popular Custom PC Parts Ranking and Selection Rate by Specification [Statistical Data]

High-Speed Data Transfer

Because the M.2 slot supports the PCIe standard, it has a much higher maximum data transfer speed compared to the SATA standard.

Therefore, NVMe SSDs are also fast to match this standard.

Let’s look at the data transfer speeds of storage by standard.

PCIe has versions, and the speed changes depending on the version.

The versions themselves are compatible, so even if the PCIe version of the motherboard’s M.2 slot is lower, it will still work, but the data transfer speed will be limited to the lower version.

In other words, if the goal is to maximize the speed of the latest Gen5 NVMe SSD, choose a motherboard with an M.2 slot that supports PCIe 5.0.

As shown, compared to SATA SSDs, NVMe SSDs are extremely fast, making them ideal for OS and app startup, game load times, and transferring large data files of several GB.

No Need for Power or Data Transfer Cables

Because the M.2 slot is mounted on the motherboard, no power or data transfer cables are needed.

With traditional SATA SSDs, two cables were needed: one for power and one for data, but M.2 SSDs handle both power and data transfer through the motherboard slot, so these cables are unnecessary.

This makes the inside of the PC tidier and assembly easier.

Also, because no cables are needed, the risk of failure or poor contact is reduced.

More Compact Design

The M.2 slot allows for a more compact installation compared to SATA SSDs.

While SATA SSDs are installed in 2.5-inch or 3.5-inch bays in the PC case, NVMe SSDs are mounted on the motherboard, saving space.

Because the storage itself is small, there are more options for building custom PCs using small PC cases.

M.2 Slot Sizes

There are four sizes for M.2 slots: M.2 2230, M.2 2242, M.2 2280, and M.2 22110.

The first two digits indicate the width, which is fixed at 22mm.

The remaining digits indicate the length, and the main differences in use are based on this length.

M.2 2280: Standard Size / For NVMe SSDs

M.2 2280 is 22mm wide and 80mm long, and is the most standard and widely used model among M.2 SSDs.

It is used in most desktop PCs, and when building a custom PC, this size of NVMe SSD is usually installed.

The motherboard’s M.2 slot must also support this size, but since the M.2 slot is mostly used for NVMe SSDs and manufacturers know this, most slots support this size.

The feature of M.2 2280 is that its length allows many NAND chips to be mounted on the board.

This means there are large capacity models such as 2TB and 4TB, and M.2 2280 NVMe SSDs are especially popular in gaming PCs and high-end creator laptops.

Also, many high-speed PCIe models are available, making them very suitable as system drives for the OS.

M.2 2230: For Ultra-Compact Devices

M.2 2230 is a small M.2 SSD with a width of 22mm and a length of 30mm, an extremely compact size standard.

Because of its short length, it is mainly used in ultra-compact laptops, tablets, and some small PCs, making it ideal for devices with limited internal space.

It is also used not only for storage but also for communication cards such as Wi-Fi and Bluetooth modules.

M.2 2242: For Laptops

M.2 2242 is 22mm wide and 42mm long, making it slightly longer than M.2 2230.

This size is especially used in thin laptops and compact desktop PCs, and like M.2 2230, can be installed in limited spaces.

It is mainly used for storage purposes.

M.2 22110: For Servers and Workstations

M.2 22110 is 22mm wide and 110mm long, making it the longest size in the M.2 standard.

Thanks to its length, it is often used in environments that require long hours of heavy workloads, such as servers and workstations.

M.2 22110 can mount a large number of NAND chips on the board, so high-performance and large-capacity models are available.

This size is mainly used in enterprise products and motherboards with solid cooling measures, and since supported devices are limited, it is important to always check compatibility before purchasing.

In addition, for enterprise use, reliability and durability are important, so features such as error correction (ECC), data protection, power management, power control chips, RAID function chips, and encryption (hardware encryption) may be included.

Because it is longer than other sizes, not only can it mount large-capacity NAND chips, but it is also easier to implement additional components needed for advanced enterprise features.

Types of M.2 Slot Keys

M.2 slots have several types of insertion shapes, called keys.

A key is a notch that controls physical compatibility according to the connection standard or purpose, preventing the wrong device from being installed.

A / E Key: For Wi-Fi and Bluetooth Modules

A key and E key are mainly used for connecting Wi-Fi and Bluetooth modules.

They generally support sizes such as 2230 and 2242, and are often used when adding wireless communication functions.

A key and E key can be used individually or combined.

This allows for a wider variety of modules to be connected.

M Key: For NVMe SSDs

The M key shape has a notch on one side of the slot.

The M key is mainly for NVMe SSDs, and usually uses PCIe for high-speed data transfer.

B Key: For SATA Standard

The B key shape has two notches at the end of the slot.

The B key is mainly for SATA standard SSDs.

While NVMe SSDs are common for M.2 slots, some devices use the M.2 slot shape but connect via SATA.

The B key can also use PCIe x2 lanes, so it supports not only SATA but also some PCIe connections.

However, compared to the M key’s PCIe, data transfer speed is slower, so it is rarely used.

Be Careful with M.2 Slot Compatibility

M.2 slot sizes and keys have compatibility, and if these are incorrect, parts cannot be physically installed.

Therefore, when selecting parts, check the size and key of the part to be installed, and make sure the motherboard has an M.2 slot that supports that size and key.

Also, to maximize storage data transfer speed, attention must be paid to the PCIe version.

M.2 Slot Sizes

There are four sizes for M.2 slots, so it is necessary to check if the slot supports the required size.

After checking the size of the part to be installed, check if the motherboard’s M.2 slot supports that size.

Generally, the motherboard’s M.2 slot supports multiple sizes.

This is similar to how CPU cooler sockets support multiple shapes.

Not only do they support multiple sizes, but most NVMe SSDs are M.2 2280, and manufacturers cover the sizes in demand.

Therefore, unless there are special circumstances, even if a motherboard is chosen at random, there will be an M.2 slot that can install an NVMe SSD.

However, in small PCs or laptops, space is limited, so only M.2 cards of certain short lengths may be supported. Always check before purchasing.

Types of M.2 Slot Keys

M.2 slots have several types of insertion shapes, called keys.

This determines what parts can be connected and also prevents the wrong parts from being installed.

After checking the key of the part to be installed, check if the motherboard’s M.2 slot supports that key.

The type of key is largely determined by the type of product. Generally, NVMe SSDs use the M key, and Wi-Fi/Bluetooth modules use the A key/E key.

As with M.2 slot sizes, unless there are special circumstances, an M.2 slot with an M key is implemented, so there is no problem installing an NVMe SSD.

PCIe Version

NVMe SSDs operate with the PCIe standard, so the PCIe version is also important.

Therefore, to maximize storage data transfer speed, the motherboard’s M.2 slot must support the PCIe version of the storage.

In other words, the PCIe version of the M.2 slot must be equal to or higher than that of the storage.

The versions themselves are compatible, so even if the PCIe version of the motherboard’s M.2 slot is lower, it will still work.

However, the data transfer speed will be limited to the PCIe version of the motherboard, so be careful.

For example, if the goal is to maximize the speed of the latest Gen5 NVMe SSD, choose a motherboard with an M.2 slot that supports PCIe 5.0.

Summary: Usually Fine for SSDs, But Check Key and Size!

This article explained in detail the basic knowledge of the motherboard’s M.2 slot, including slot sizes and keys related to compatibility.

Here are the key points again.

The M.2 slot is widely used for connecting NVMe SSDs, Wi-Fi, and Bluetooth modules, and has become popular as a replacement for the mSATA slot.

Using an NVMe SSD enables much faster data transfer compared to SATA SSDs.

However, since M.2 slots have slot sizes and keys, it is necessary to check if the part to be installed is compatible with the motherboard’s M.2 slot.

Especially since M.2 slots are often used for installing NVMe SSDs, most motherboards have an M.2 slot with the size (2280) and key (M key) needed for NVMe SSDs.

If the wrong type is chosen, it cannot be inserted, so be careful when selecting parts.

This article also explains how to choose based on motherboard standards, part names, performance, and compatibility.

≫ Related article: How to Choose a Custom PC Motherboard [Performance / Features / Compatibility]

あわせて読みたい

PC Parts Estimation & Compatibility Check Tool

Automatically checks each component you need when selecting parts for a custom-built PC—perfect for beginners.