Modern SSD memories are now widespread. They reach much higher speeds than conventional hard drives, so you can work on the computer much faster. Due to the acute drop in the price of SSDs, sales figures have increased enormously.
However, current SSDs could read and write much faster, but they are limited by the bus used. The SATA 3 standard provides a maximum transfer rate of 6 GBit/s so that in practice you can read and write a maximum of 550 MB per second from the SSD. This limitation can be circumvented by connecting the SSD storage via PCI Express.
Corresponding PCIe cards have been available for a long time, but are significantly more expensive than SATA SSDs of the same capacity. In addition, the PCIe slots are only available in stationary computers, so laptops were initially left out unless manufacturers used proprietary solutions, such as Apple in the MacBook Air.
Bootable SSD for your PC?
While the bootability of M.2 SSDs was still a problem when it was introduced, all common M.2 SSDs are now bootable on current mainboards without any problems. Are you just looking for a bootable M.2 SSD for your desktop PC or notebook?
Then you will find the right M.2 SSDs with SATA connection here. Just choose the right size for your budget: look for a SATA-M.2 SSD If you have a current mainboard with NVMe or PCIe for M.2 support, you will find significantly faster SSDs here (note the speed): Find a PCIe M.2 SSD
What is NVMe?
NVMe, Non-Volatile Memory Express, is a data transfer protocol similar to SATA. In contrast to SATA, however, NVMe is directly connected to PCI Express and can therefore offer significantly higher transfer rates. All current M.2 SSDs for PCIe, therefore, use NVMe as a protocol.
Advantages of M.2:
In order to eliminate these disadvantages, Intel introduced the Next Generation Form Factor, NGFF for short, in 2012. NGFF modules are extremely compact, so they can also be used in mobile computers and mini-computers.
They also enable connection via up to four PCI Express 3.0 lanes. This would provide a bandwidth of 32 GBit/s, i.e. more than five times that of SATA 3. NGFF is now marketed under the name M.2.
Both names are in use and used interchangeably. Incidentally, the M.2 specification is very general. There are also M.2 plug-in cards for WLAN, Bluetooth, GPS, NFC, and some other functions. For most end users, however, the M.2 port should only be of interest for SSDs.
Since M.2 can also provide SATA, you have to pay attention to the right components so that you don’t have the same speed limits again. But more on that below. If you already know that you want to buy an M.2 SSD and are not interested in the background, you will find compact purchase advice and current recommendations from the editors in our M.2 SSD purchase checklist.
M.2:
Card sizes The specification of M.2 provides for different module sizes. In practice, plug-in cards that are only 22 millimeters wide are currently used in various lengths. M.2 allows lengths of 30, 42, 60, 80, or 110 mm. M.2 SSDs with a length of 42, 60, and 80 millimeters are currently available.
The dimensions of an M.2 card are encoded by giving the width and length in millimeters in a row. So an M.2 2260 is 22 mm wide and 60 mm long. The maximum length of an M.2 module is determined by the place of use. Before you buy, you should make sure that the maximum length is possible. Especially in mobile or very compact computers, there is not always room for 8 cm long plug-in cards.
In the opposite case, it is of course possible to use shorter cards, e.g. an M.2 2242 in an M.2 port for up to 60 millimeters. Only the socket for the locking screw is not necessarily available for all lengths, this depends on the mainboard or notebook used.
The Crucial M500 is an M.2-2280 card. Easily recognizable: the two cutouts on the connection for the Key B+M coding. Source: Micron Technology In some applications where there is very little space available, the height of the M.2 card can also be relevant.
There are M.2 cards populated on one side (S1 to S3) as well as on both sides (D1 to D5). The components on the card may have certain maximum heights, which are currently not relevant for the end user in practice.
What do the keys of M.2 cards mean?
Depending on which interfaces an M.2 port provides, a certain type of connection is used. These so-called keys require M.2 plug-in cards with cutouts at certain points so that only suitable plug-in cards can be used cards fit into the respective M.2 port.
However, only the Key M is relevant in practice. Many M.2 SSDs also offer a Key B with a 6-pin recess on the right side. However, this only support a maximum of PCIe x2 or SATA and is only supported by very few mainboards – but by many external USB housings.
Plug-in cards with Key M have a notch on the left side, five pins from the edge. Key M supports up to four PCIe lanes and SATA. Most M.2 SSDs currently available are Key B+M. They both have cutouts and can therefore be plugged into Key B and Key M ports.
Buyers need to make sure the port and module support the same key, otherwise, the M.2 card will not fit. The so-called “keys” ensure that only compatible plug-in cards fit into an M.2 port. Key B, Key M, and Key B+M are currently in use. Source: Scotland / NikNaks / CC BY-SA 3.0
SATA or PCIe for M.2 SSDs?
As mentioned above, M.2 can provide both SATA and PCI Express interfaces. This means that M.2 SSDs are not necessarily faster than traditional 2.5-inch SSDs with a SATA 3 interface.
In fact, many of the commercially available M.2 SSDs are connected to SATA 3. They are therefore subject to the same speed limits and offer no speed advantage. So why are there M.2 SSDs with SATA connectors? Compared to the faster PCIe SSDs, they were initially cheaper and took up less space than 2.5-inch drives.
For this reason, there is often only one M.2 port in current ultrabooks and notebooks, so that devices that are as compact as possible can be offered. M.2 SSDs connected via PCIe offer a full-speed advantage. These then use the much faster NVMe protocol for data transmission instead of the SATA protocol.
Although the prices are correspondingly higher, these SSDs can read and write data much faster. But: there are also differences with PCI Express: Depending on how many lanes are used, the speed is slower or faster.
With PCIe 2.0, 5 GBit/s are possible per lane. A connection via two lanes with PCIe x2 limits the bandwidth to 10 GBit/s, which is around 50 percent faster than SATA 3. When using four lanes, the limit is therefore 20 GBit/s and corresponding SSDs allow SATA-3 -Models far behind. The PCIe 5.0 standard for SSDs is brand new. Transfer rates of up to 15000 MB/s are possible here.
At the start of the M.2 SSDs, the golem.de editorial team tested the first two M.2 SSDs with a PCIe connection and compared them with a Samsung 840 Pro. The average reading speed of the 840 Pro was 540 MB/s in the test.
When connected via two PCIe lanes, the Plextor M6E and the Samsung XP941 achieved speeds of 748 and 797 MB/s, respectively. This roughly corresponds to the expected increase of around 50 percent. Significantly higher speeds are now possible – with M.2 SSDs that support PCIe 4.0.
This means that 16 GBit/s are available per lane and therefore a total of 64 GBit/s bandwidth. For example, the Samsung SSD 980 Pro M.2 or the Samsung SSD 980, which achieve speeds of up to 7000 MB/s and thus already achieve the maximum of PCIe 4.0 x4 when reading.
Of course, the prerequisite for this is a corresponding mainboard, such as many current Intel mainboards of the latest generation, which support the connection of an M.2 SSD via PCIe 4.0 x4.
The new M.2 SSDs with PCIe 4. 0 connection have been on the market since the summer of 2020. Compared to the predecessor PCIe 3.0, the speeds have been improved again. Depending on the model, up to 7500 MB/s can be achieved here.
These M.2 SSDs are designed for PCIe 4.0. With the release of the new 12th generation Intel Core I processors and the associated Z690 mainboards, M.2 ports with PCIe 5.0 connections are now available for the first time.
However, matching M.2 SSDs are not yet available. The new standard, which will not be able to come up with corresponding SSDs until summer 2022 at the earliest, should double the performance again. The same applies to AMD’s new AM5 socket. Seagate FireCuda 530 SSD Best offer from:66.08€incl.
Shipping 237 other prices and providers Samsung SSD 980 PRO NVMe M.2 Best offer from: 64.89 € incl. shipping 218 other prices and providers Crucial P5 NVMe PCIe SSD Best offer from:62.90€incl. Shipping 6 other prices and providers More recommendations here: M.2 SSD purchase checklist
Mainboards with M.2:
Many Intel mainboards of the 9 series offered an M.2 port for the first time. Unfortunately, Intel only provided the connection with two PCIe 2.0 lanes, so that SSDs that support four lanes are slowed down on such boards.
Nevertheless, this interface is around 50 percent faster than SATA III. If you own such a board, you can save the surcharge for supporting four lanes with the M.2 SSD. If you still want to use the full speed of four lanes, you have to use an adapter for a PCIe port (see next section). ASRock’s Fatal1ty 990FX-Killer was the first motherboard with M.2 port.
The ASRock Z97 Extreme6 was the first mainboard to provide an M.2 port directly with four PCIe 3.0 lanes so that the other boards are not limited here. In the meantime, many mainboards of the new Intel generations with sockets 1700, 1200, 1151, and 2011v3 or 2066 are equipped with such a connection.
Intel motherboards with PCIe M.2 ports Thanks to the AM4 chipset, there are also many models with an M.2 port among AMD mainboards. Curiously, AMD was even a pioneer and presented the ASRock Fatal1ty 990FX Killer, the first mainboard ever with M.2. With older mainboards for the AM3+ socket, however, the connection is sometimes still made via two PCIe 2.0 lanes or via SATA.
So check the specifications carefully beforehand. Current AMD mainboards with AM4 sockets also offer PCIe 4.0. The AM5 socket even includes PCIe 5.0. AMD motherboards with PCIe M.2 ports By the way, the Australian colleagues from Ramcity have already tested many mainboards and M.2 SSDs for compatibility.
Operate M.2:
SSDs on old mainboards M.2 SSDs can also be used in older computers using adapters. There are adapters for SATA SSDs that turn an M.2 SSD into a 2.5-inch drive.
However, this solution does not bring any speed advantage and costs more than a 2.5-inch SSD, so this should only be of interest in very special cases. Adapters, like this model from Delock, enable the operation of M.2 SSDs in a PCIe slot.
The use of an M.2 SSD with PCIe interface brings a real plus in speed. Converters are commercially available that can be used to operate these SSDs as PCI Express cards. Such an adapter was also used in the above test by the Golem editorial team.
Together with the Samsung XP941, a reading speed of 1.2 GB/s was achieved. If the older mainboard has a free PCIe slot with four or more lanes, such as an M.2 to PCIe adapter makes the most sense. The only thing to keep in mind is that not all of these adapters are bootable.
So if you want to run an operating system on an M.2 SSD via a PCIe adapter, you should find out more about the PCIe adapter beforehand.
But a bios that is too old can also throw a spanner in the works. There are PCIe to M.2 adapter cards here. The OCZ Toshiba RD400 can even be purchased complete with a PCIe card adapter. Particularly practical: if you switch to a mainboard or notebook with a built-in M.2 port in the future, the SSD can simply be removed from the converter and reused. There are recommendations for PCIe adapters here: M.2 SSD purchase checklist
Conclusion:
In the meantime, M.2 SSDs with a SATA interface are actually hardly relevant anymore. If they used to be attractively priced, this advantage has long since disappeared. Therefore, we only recommend such an M.2 SSD if there is no other option, such as older notebooks that only have an M.2 SATA port. M.2 shows the full-speed advantage when the connection is made via PCI Express.
The following applies: more lanes are better and PCIe 5.0, 4.0, and 3.0 are faster than PCIe 2.0. However, all components must then support this connection. For example, using a PCIe x4 SSD in an x2 port will slow it down. What experiences have you had with M.2? What questions can we still answer for you?
