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Overview of M.2 SSDs

Written on August 15, 2014 by Matt Bach


When it comes to the "snappiness" of a system, the hard drive is one of the most important hardware components in a PC. The faster the drive, the faster the system boots into the OS, the faster programs launch, and the faster files save. The introduction of SSDs a number of years ago was a major step forward from traditional platter drives, but SSDs have recently hit a performance wall with the existing SATA III protocol where they simply cannot run any faster. 

M.2 is a new form of connectivity that allows a SSD to connect directly to the PCI-E bus rather than going through a SATA controller. By bypassing the SATA controller a M.2 drive is only limited by the speed of the drive itself and the generation/number of PCI-E lanes it uses. By using just four PCI-E 2.0 lanes, a M.2 drive can theoretically have a maximum throughput as high as 2GB/s. To put this into perspective, that is over three times faster than the SATA III limitation of 600MB/s!

However, not everything is quite so rosy with M.2. Unlike SATA drives - where every drive is the same physical size and uses the same cables - M.2 allows for a variety of physical dimensions, connectors, and even multiple logical interfaces. To help our customers understand the nuances of M.2 drives we decided to publish this overview of the current M.2 specifications.

Physical size and connectors

Unlike SATA drives, M.2 allows for a variety of physical sizes. Right now, all M.2 drives that are intended for use in PCs are 22mm wide, but they come in a variety of lengths. To make it easier to tell which drives can be mounted on a motherboard or PCI-E card, the width and height of both the drive and slot is usually expressed in a single number that combines the two dimensions. For example, a drive that is 22mm wide and 80mm long would be listed as being a 2280 (22mm x 80mm). Common lengths for M.2 drives and mounting right now are 30mm (2230), 42mm (2242), 60mm (2260), 80mm (2280), and 110mm (22110).

In addition, there are two types of sockets for M.2: one with a "B key" and one with a "M key".

M.2 to PCI-E x4 adapter that can take multiple lengths of drives

M.2 socket types

B+M keyed drive (left) and a M keyed drive (right)

The different keys are what indicated the maximum number of PCI-E lanes the socket can use and physically limit what drives can be installed into the socket.. A "B key" can utilize up to two PCI-E lanes while a "M key" can use up to four PCI-E lanes. Right now, however, the majority of M.2 sockets use a "M key" even if the socket only uses two PCI-E lanes. As for the drives, most PCI-E x2 drives are keyed for B+M (so they can work with any socket) and PCI-E x4 drives are keyed just for M. 

This is confusing at first since it is much more complicated than SATA, but all of this information should be listed in the specs of both the drive and motherboard/PCI-E card. For example, the ASUS Z97-A lists the M.2 slot as "M.2 Socket 3, with M Key, type 2260/2280" so it supports drives that are 22mm wide and either 60mm or 80mm long with a M key.

M.2 logical interfaces

In addition to the different physical sizes, M.2 drives are further complicated by the fact that different M.2 drives connect to the system through three different kinds of logical interfaces. Currently, M.2 drives can connect through either the SATA controller or through the PCI-E bus in either x2 or x4 mode. The nice thing is that all M.2 drives (at least at the time of this article) are all backwards compatible with SATA so any M.2 drive should work in a M.2 socket that uses SATA - although they will be limited to SATA speeds. At the same time, not all M.2 sockets will be compatible with both SATA and PCI-E - some are either one or the other. So if you try to use a PCI-E drive in a SATA-only M.2 slot (or vice-versa) it will not function correctly.

M.2 PCI-E drives should really be used in a socket that supports the same number of PCI-E lanes as the drive for maximum performance, although any M.2 PCI-E drive will work in either a PCI-E x2 or PCI-E x4 socket provided they have the same key. However, if you install a PCI-E x4 drive into a PCI-E x2 socket it will be limited to PCI-E x2 speeds. At the same time, installing a PCI-E x2 drive into a PCI-E x4 socket will not give you any better performance than installing it into a PCI-E x2 socket.

Basically, what it comes down to is that even if a M.2 drive physically fits into a M.2 socket, you also need to make sure that the M.2 socket supports the type of M.2 drive you have. In truth, the only time a M.2 drive shouldn't work at all even through the keying matches is if you try to use a M.2 SATA drive in a M.2 PCI-E only socket.

Performance Range

Since this article is about M.2 drives in general, we are not going to give any specific benchmark numbers but rather talk in general, theoretical terms of what is possible with M.2. If you are looking for benchmarks, we recommend reading our Samsung XP941 & Plextor PX-G256M6e M.2 Qualification article.

Since M.2 drives right now come in three tiers (SATA, PCI-E x2, and PCI-E x4), there are also three tiers of possible performance. However, due to the flexible nature of PCI-E, future M.2 drives may come in an even wider range of speeds.

M.2 Drive Throughput
by Connection
Maximum Throughput
Est. Real-World
Maximum Throughput
SATA III 6.0 Gb/s (750 MB/s) 4.8 Gb/s (600 MB/s)
PCI-E 2.0 x2 8 Gb/s (1 GB/s) 6.4 Gb/s (800 MB/s)
PCI-E 2.0 x4 16 Gb/s (2 GB/s) 12.8 Gb/s (1.6 GB/s)
PCI-E 3.0 x4 32 Gb/s (4 GB/s) 31.5 Gb/s (3.9 GB/s)

The "theoretical maximum throughput" is the number that a lot of vendors and manufactures like to use when talking about SATA or PCI-E, but there is a certain amount of overhead when transferring data that prevents a drive from ever hitting this theoretical throughput. Taking the overhead due to encoding into account gives us the "estimated real-world maximum throughput". This does not mean that every M.2 PCI-E 2.0 x4 drive can reach speeds of ~1.6 GB/s, but simply that this is roughly the best possible speed any M.2 PCI-E 2.0 x4 drive can achieve.

What is interesting to see is that a M.2 drive using PCI-E 2.0 x2 only has a 33% potential speed increase over SATA III. This is still notable, but is not exactly revolutionary. Where M.2 gets exciting is with PCI-E 2.0 x4 which has a real-world maximum throughput of 1.6 GB/s. To put this into perspective, that is only a hair less than three times the throughput of SATA III. You would need three SATA III SSD drives in RAID 0 to get the same potential performance of a single M.2 PCI-E 2.0 x4 drive!

Since M.2 drives use the PCI-E bus, the maximum throughput will not always be limited to PCI-E 2.0 x4. While there are not any PCI-E 3.0 x4 M.2 drives right now, as with all technology it is really only a matter of time before they are developed. When that happens, we may eventually see M.2 drives that can run at almost 4GB/s! Current storage technology isn't quite up to this task yet, but in a few years it very well might be.

Update Dec 2015: PCI-E 3.0 x4 drives such as the Samsung 950 Pro are now available. This drive has ~1.5GB/s write performance and 2.5GB/s read performance. 

PCI-E lane complications

Even this early in M.2 development, there are already M.2 drives like the Samsung XP941 that have read speeds that are twice as fast as any SATA-based SSD. However, there is a very finite number of PCI-E lanes in a system and a M.2 PCI-E drive will need to use a certain number of them. This means that instead of checking to make sure your motherboard has enough SATA ports, you instead have to check that you have enough PCI-E slots and lanes. Many motherboards have plenty of PCI-E x16 slots, but it becomes a problem when you realize that usually very few of those slots can actually run at x16 speeds.

Asus Z97-A PCI-E slots

For example, say you have a Asus Z97-A and want to install a M.2 x4 drive using a PCI-E adapter. That motherboard has two PCI-E x1 slots and three physical PCI-E x16 slots. The two PCI-E x1 slots don't have the necessary number of PCI-E lanes for a M.2 drive so they cannot be used. For the x16 slots, it turns out that the bottom PCI-E x16 slot is actually only capable of x2 speeds, so that slot will not allow for the full speed of a M.2 x4 drive. The primary x16 slot is likely needed for the GPU so it is also not available to be used. Finally, the second x16 slot is capable of x8 speeds so it will work for the M.2 x4 drive, but using that slot will actually reduce the primary slot (and thus the GPU) to x8 speeds. We've shown in the past that modern GPUs do not show any performance loss by running at x8 speeds, but it still is not ideal. And remember, this is just to add a single M.2 x4 drive and doesn't take into account other PCI-E devices you might have like sound cards or wireless cards. If you want to add a second M.2 x4 drive, you are pretty much out of luck until someone releases a M.2 to PCI-E adapter that can handle multiple drives in a single slot.

The PCI-E lane issue is less of a problem on X79 or Xeon E5 systems since the CPU (and thus the motherboard) has more PCI-E lanes available, but you still need to plan it out ahead of time to make sure you don't run into any surprises. Hopefully future Intel CPUs will add more PCI-E lanes to make this less of an issue, but for now this is the biggest limitation we see in terms of M.2 adoption.

M.2: drives of the future?

While this article is mostly about M.2 SSDs, our excitement about M.2 is not just limited to just that. Since M.2 is essentially just a PCI-E interface, M.2 can be used for almost anything including WiFi, Bluetooth and GPS. Imagine a laptop where instead of multiple connectors for different devices, a laptop could just have four M.2 slots and that's it. Do you want to install two M.2 drives, a WiFi card and a GPS card? No problem. Or maybe you would rather make a mobile file server and use four M.2 drives in RAID. The point is that you can put any M.2 device in any M.2 slot and it would just work. 

As for SSDs, the complication of PCI-E lanes and physical compatibility makes M.2 a bit more complicated than SATA, but M.2 adds so much performance potential that we believe they will soon become a staple in any high-performance system. The price of mid-range M.2 drives like the Plextor PX-G256M6e is already very comparable to SATA-based SSDs so it doesn't cost much to easily boost performance over SATA drives. High performance drives like the Samsung XP941 are more expensive right now, but we expect them to come down in price as the technology matures and demand increases.

Overall, M.2 is a technology that we at Puget Systems are making sure to stay on top of. Hard drives have long been one of the biggest bottlenecks in the average PC, but M.2 has the potential to finally change that. Over 1.2GB/s read performance with an early edition M.2 drive is simply amazing, and makes us very excited to see what M.2 drives will be capable of in the future.

Update Dec 2015: PCI-E 3.0 x4 drives such as the Samsung 950 Pro are now available. This drive has ~1.5GB/s write performance and 2.5GB/s read performance. 

Recommended Reading

If you are interested in M.2 drives, we have a number of other articles you may be interested in:

Tags: m.2, SSD
Avatar Bayfront Benny

Please keep updating this information as new drives become available on a retail basis. Thanks for your informative articles on this subject (the other article on the XP941 and PX--G256M6e.

Posted on 2014-09-26 19:30:34
Avatar Mehmet MUHCI

You have given all of the information that I wonder about M.2 socket.
Thanks a lot for that excellent article.

Posted on 2014-11-02 16:35:19
Avatar Siddharth Parmar

Can we use a SSD connected by M.2 as the main drive on which we can install the OS and other necessary software ?

Posted on 2014-11-05 03:26:05

You can... sometimes... Usually what it comes down to is what controller the M2 drive uses. Unlike SATA drives where the controller is on the motherboard, on M2 drives the controller is built into the drive itself. Right now, we are using the Plextor M6e and Samsung XP941 drives. The Plextor we have been able to install onto with every motherboard we've tested in both BIOS and UEFI mode, but the Samsung only works on a few motherboards and only in UEFI mode.

We have a full list of which motherboards both drives worked on at http://www.pugetsystems.com...

Posted on 2014-11-05 19:17:03
Avatar diablo

How is SATAexpress different than M.2

Posted on 2014-11-20 19:59:44
Avatar OptimusPrimus

Plextor PX-G256M6e is not as good as the specs indicate. You're better off using a SATA M.2 atm or regular SATA SSD until some "real" performer M.2 PCIe cards come out.

Posted on 2015-02-09 01:36:19

You mean like the Samsung XP941, also mentioned above? We have a couple of additional m.2 articles that cover performance of those drives if you're interested.

Posted on 2015-02-09 01:53:37
Avatar David

Matt, I just want to say 'thanks' for some great articles that you've written (including this one). This is one of the most thorough write-ups on M.2 that I've come across. You explain the pros and cons of M.2 quite well, especially considering the fact it is going to be confusing for many people over the next 2-3 years at least.

Just a thought about one subject you didn't cover: AHCI. While I'd expect most motherboards that come with an M.2 connector to support UEFI, my understanding is that doesn't mean the BIOS will necessarily support NVMe out-of-the-box. And of course depending on your OS, you may or may not find a NVMe driver atm. So, someone could theoretically purchase a mobo with let's say an M.2 M-key socket, and a corresponding SSD, plug them in and get sub-optimal performance relative to their expectations. I see this as one of many reasons why M.2 is going to confuse the heck out of most people in the short term. If peak disk performance is a priority, it's no longer as easy as picking the fastest SATA 3 disk you can find. Those days are gone.

What are your thoughts on running M.2 PCI-e x2 or x4 SSDs over AHCI versus NVMe? Do you think I'm off the mark here? Have you experimented between the two (AHCI vs. NVMe)?

Posted on 2015-06-30 21:46:24

I'm glad this article was useful! You are right, a section about AHCI vs. NVMe would probably be a good addition. Maybe a section about U.2 as well not that that connector has finally been named...

As far as I know (and I haven't specifically researched this so I could be wrong) AHCI is usually slower, but is more compatible. If you are using current generation hardware, I think NVMe should be the way to go since firmware/driver support has been pretty decent from what we have seen. With anything older than Haswell/Haswell-E, though, you will probably run into problems using NVMe as a boot drive. As a storage drive we haven't had any problems with NVMe on anything we have tested though.

Posted on 2015-06-30 23:55:50
Avatar David

Matt.. separate question/thought.... Doesn't PCI-e 2.x = 5Gb/s per lane? Is that a typo in your chart above (i.e. shouldn't that be 10Gb/s and 20Gb/s for PCI-e 2.x 2x/4x)? Or is the throughput of PCI-e 2.x over M.2 different from a PCI-e card connected directly to a PCI-e slot?

Also, the overhead on PCI-e 2.x is 20% (2/10), but on PCI-e 3.x it is 1.5% (2/130). Unless the PCI-e throughput is slower on M.2 versus a native PCI-e connector, I believe the PCI-3.0 x4 real-world speed should be around 31.5 Gb/s or 3,938 GB/s.

Posted on 2015-07-02 16:15:03

From what I can find, PCI-E 2.X has a per lane transfer rate of 5GT/s - not 5Gb/s - which works out to 500 MB/s (or 4Gb/s). So I'm pretty sure the chart is correct.

As for the PCI-E 3.0 overhead, I didn't realize that PCI-E 3.0 used a new encoding scheme that lowers the overhead to just 1.5%. I'm not 100% sure that PCI-E 3.0 x4 M.2 drives will ever hit 3.9GB/s but you are right that that would be the theoretical max for those devices. I'll update the chart to 3.9GB/s

Posted on 2015-07-02 18:36:57
Avatar David

Well, I believe you are partially correct, but that your math is a bit off. It looks like you accounted for the TLP overhead twice in your calculations. Let's see if we can hash this out.

PCI-E 1.x and PCI-E 2.x clock 2.5GHz and 5.0GHz respectively. PCI-E 3.x is 8GHz/s. In PCI-Express' world, there is 1 bit transferred per clock cycle, resulting in 2.5G/s and 5.0G/s transfers for PCI-E 1.x / 2.x respectively. PCI-E 3.x gets an effective double boost in performance over PCI-E 2.x because the overhead drops from 20% to ~1.5% (PCI-E 2.x to PCI-E 3.x), due to more efficient TLP encoding.

Alright, so we know there are 5.0G transfers per second with PCI-E 2.x. Next question is how many bits get passed in one physical Transfer? Now, in the case of PCI-Express, the theoretical throughput is one T[ransfer] = one bit (per direction, but that is a whole other discussion). To wit, 5GT/s would equate to 5G bits of raw throughput at the Transaction layer for PCI-E 2.x. So, the raw theoretical bandwidth is 5Gb per second per lane. Your PCI-E 2.0 x2 row shows 8Gb/s or (4x2)Gb/s per lane. Basically, you subtracted the encoding overhead (20%) and then posted the adjusted number (10 - 20% = 8), but the theoretical figure should not be adjusted for the encoding. You correctly made the 20% adjustment for 8b/10b encoding when converting your theoretical value to your "Real-World" column, but at that point you were calculating 80% of the 80% figure.

So, you see there is the problem. The first 20% reduction should be backed out, which would give you the proper 5G/s per lane transfer rate and the proper real-world rate (i.e. 5Gb/T = 5Gb/s x 2 lanes = 10Gb/s raw value). Then in your far right column you'll process the 20% overhead in converting to 'real world' throughput, so you'll have 10Gb/s - 20% = 8Gb/s / 8 bits per byte = 1 GB/s = 1,000MB/s. The 4x lane calculations should of course be double the 2x lane figures.

Thus back to your conclusion of 500MB (per lane), which is correct but you had that in the wrong column. Perhaps you originally worked the math backwards and forgot to add the TLP overhead???

Regardless, it is a confusing subject for sure! And kudos to you for your timely replies to my verbose posts! :-)

Posted on 2015-07-02 21:49:09
Avatar Vincent

Theoretical Maximum Throughput column is before encoding overhead for SATA III and PCI-E 3.0, so PCI-E 2.0 should be the same.
Est. Real-World Maximum Throughput applies overhead cost to Theoretical Throughput, so figures for PCI-E 2.0 are incorrect.
Overhead for SATA-III and PCI-E 2.0 is 20% with 8b/10b encoding.
Overhead for PCI-E 3.0, 4.0 and 5.0 is 1.5% with 128b/130b encoding.

Correct figures should be:
Connection Type - Raw Data Throughput - Payload Data Throughput
SATA III - 6 Gb/s - 4.8 Gb/s (600 MB/s)
PCI-E 2.0 x2 - 10 Gb/s - 8 Gb/s (1000 MB/s)
PCI-E 2.0 x4 - 20 Gb/s - 16 Gb/s (2000 MB/s)
PCI-E 3.0 x4 - 32 Gb/s - 31.5 Gb/s (3938 MB/s)
PCI-E 4.0 x4 - 64 Gb/s - 63 Gb/s (7877 MB/s)
PCI-E 5.0 x4 - 128 Gb/s - 126 Gb/s (15754 MB/s)

The first PCI-E 4.0 drives have been announced and the PCI-E 5.0 standard has been finalised recently.

Posted on 2019-06-04 06:09:35
Avatar Manny Alonzo

Can a M + B keyed SSD be used upside down on a M-keyed Asus Z97K motherboard?

Posted on 2015-08-05 04:09:37
Avatar Tom

Hi, thank you for the interesting article, it helps a lot, but recently I have swapped drives in HP EliteBook G1 ( M.2 SATA Intel SSDSCIHF120A4H ) and (M.2 PCIe SanDisk A110 - HP Z Turbo Drive) from HP ZBook 15u G2, and got an opposite towhat you said "In truth, the only time a M.2 drive won't work even through the keying matches is if you try to use a M.2 SATA drive in a M.2 to PCI-E adapter since it doesn't have a connection to the SATA controller." - the M.2 SATAT drive worked in the M.2 PCIe socekt, while M.2 PCie drive wouldn't work in M.2 SATA socket. The further down the M.2 patch the more confused I get. Would you be able to look into it and explain ? Cheers

Posted on 2015-09-09 11:33:09
Avatar Mike

I have an Asus z170-a board with a Samsung pcie m.2 card plugged into the m.2 slot on the board. I loaded the os, everything fine.
I installed my video card and the board comes on, the video card comes on , but the m.2 wont power up, and no boot. Seems that you cant run them both

Posted on 2015-09-18 01:07:02

A lot of motherboards share PCI-Express lanes between various slots and on-board features / components. I would check your motherboard manual and BIOS to make sure there aren't any settings that affect the PCI-Express lane distribution.

Posted on 2015-09-18 07:25:10

Specifically, check "Advanced -> Onboard Devices Configuration" in the BIOS and make sure "M.2 and SATA Express SATA Mode Configuration" is set to "M.2" (I believe that is what it is called. Just make sure it isn't set to SATA Express). Here is the BIOS screen you are looking for: https://www.pugetsystems.co...

If that doesn't work, make sure you are running the latest BIOS (0801 right now I believe)

Posted on 2015-09-18 18:58:33

So, if I have an M.2 SSD drive with SATA connection (according to HWInfo) then I know for sure it can't take M.2 PCIe SSD drive, right?

Posted on 2015-12-10 19:22:18
Avatar Misu el gato

So if i were to buy the asus z97-a motherboard and this adapter http://www.amazon.com/Lycom... will my m.2 ssd perform at it fullest potential or not?

Posted on 2016-01-05 18:43:29

Electrically, that adapter should work fine. It is PCI-E 3.0 x4, which matches the fastest M.2 drives available. The only issues you may run into are needing to install in UEFI mode (not an issue with the adapter, but a good thing to be aware of if you want to use the M.2 drive as your OS drive) and thermal throttling. If you have a x2 drive you shouldn't have an issue, but if you have a x4 drive I would highly recommend using an adapter that includes a heatsink. This is the adapter we use on our systems when needed, but any PCI-E x4 adapter should work: http://www.amazon.com/Bplus...

I just added a few links to the end of this article to other articles we have written you may want to look at since they cover how the drives throttle due to temperature.

Posted on 2016-01-05 19:43:50
Avatar Adrian Solonari

So, b+m will work on every m.2 slot?
Because I have one and I plugged it in my m.2 slot in laptop ( wich is looking like it's for M key) and it is not recognized by pc.
The problem is in conmector or I should search other things?

Posted on 2016-02-10 12:50:12

B+M should fit in every slot, but that doesn't mean it will always work - M.2 as a specification is still relatively new and growing which means there are lots of things that could prevent it from working. It may be that your laptop only supports SATA, but the M.2 drive is PCI-E only. Or, maybe the M.2 slot does supports SATA but you need to enable SATA mode in the laptop's BIOS. Possibly, you need to update the laptop's BIOS to improve M.2 drive compatibility. Or worst case, your laptop may simply not support M.2 fully and the manufacturer has no plans to improve support via BIOS updates (this may happen if the laptop is more than a few years old).

Posted on 2016-02-10 18:12:53
Avatar Adrian Solonari

Thank you.
When I insert it, 2 pins remain disconnected
I updated bios, laptop is new, asus rog g751jy (2015 version), however it can't see the ssd
I'm so dissapointed ;(

Posted on 2016-02-11 13:50:21

Pins remain disconnected? If the M.2 drive doesn't fit in the slot properly, then it's definitely not a M.2 slot. In fact, I think I can probably solve this mystery: I bet that is either a mSATA or Mini PCIe slot instead of M.2! That would explain the drive not fitting or working, and would fit with M.2 not showing up on the computer's specs.

Posted on 2016-02-11 15:23:57
Avatar Adrian Solonari

Here are the photos of the ssd and the port.
Amazon link on SSD - http://goo.gl/C2bNXN
My laptop port - http://postimg.org/image/6z...
The port and SSD sockets - http://postimg.org/image/bx...
How it fits without bracket, I just used tape - http://s11.postimg.org/szkk...
please help me, I have no idea what's wrong

Posted on 2016-02-11 18:07:31

That is a M.2 slot, but your mounting method is kind of scary! I did a bit more research, and what I could find (mostly from https://rog.asus.com/forum/... ) indicates that the M.2 slot in that laptop is only compatible with PCI-E based M.2 drives. The Samsung 850 EVO is a SATA-based M.2 drive, so it sounds like it won't work since even though the physical connection is fine since there is no electrical connection between the M.2 slot and the SATA controller.

It looks like your options are either to upgrade to a PCI-E baed M.2 drive or return that M.2 drive (if possible) and just buy a normal 2.5" version of the Samsung 850 EVO. Performance will be identical and you can just use the 2.5" hard drive bay that you currently have blocked with the M.2 drive. And it won't be held in place with tape, so that's good.

Posted on 2016-02-11 19:53:37
Avatar Adrian Solonari

Thank you! I'll try to sell it.

Posted on 2016-02-11 19:55:15
Avatar Lorin Boyack

Excellent write-up on M.2 Matt. It answered a lot of questions I had about the interface that the ASUS MB documentation lacked. A general question I've seen two different answers for: Is the screw that helps fasten the M.2 SSD to help physical security, or is it also required for electrical ground? I have an ASUS 970 Pro Gaming MB in an Antek cabinet and, while there's room for 42,60,80mm SSDs, there is no hole in cabinet for fastening screw. Can I just use double-stick tape to the cabinet and rely on grounding through the connections?

Posted on 2016-03-14 17:59:50

I'm pretty sure that isn't a ground. I have seen some PCI-E adapters that you can pretty clearly see that there isn't a trace from the screw to anything else on the card so it shouldn't be a problem. So double-stick tape should work as an OK solution.

Posted on 2016-03-14 18:34:11
Avatar Lorin Boyack

Thanks for the feedback Matt. I'll be doing the build in a few days and am thinking about drilling a small hole in the floorplate in the cab and see if I can coax an MB standoff ("boss") to self-tap, if I pick the right drill-bit size. Might need two stacked to get the right height. I don't like sticky-tape for heat and other reasons (ok, I'm a neat-freak). The cabinet is quite roomy and I'm not too concerned about overheating, but tape, eh. Again, I'm really glad I stumbled on your write-up on the M.2 technology, yours was the best doc I've found that had pretty much all the facts in one place. I've ordered a Samsung SM951 128 GB PCIe M.2 module that should give me 4 PCI 'lanes', and the ASUS 970 Gaming MB specs show it is an M.2 M Key socket, so if I've done my homework right, I'll have X4 performance. If the alternative was X2, I would have probably stuck with a SATA 3 6 gig SSD, as 2 lanes didn't seem to add enough performance to be worth the extra money and effort (to get this device bootable). Sorry for long ramble, maybe it will help others. If this goes Sideways, I'll post so others know if I had a compatibility and/or boot issue with my config. LB:

Posted on 2016-03-15 04:00:14
Avatar Muneer Jallouq

Is there a difference between these two form factors, 2260 and 2260DS? Will it matter when I try to install it? I know the double sided is a little thicker but my spec sheet says nothing about supporting 2260DS form factor. I cant seem to find much information online about this topic.

Posted on 2016-03-31 22:15:13

A 2260DS will just be a bit thicker due to there being chips on both sides. The M.2 connection itself should be identical, so the only thing that might be a problem is if there is enough clearance under the M.2 slot so that the card wouldn't physically hit something. I don't think I've ever seen a situation where it would be a problem (maybe in a compact laptop/ultrabook) so I doubt you will run into any issues, but there is a possibility unless you can tell if there is enough clearance.

Posted on 2016-03-31 22:43:20
Avatar Adondriel

This was very helpful, thank you. I was confused when my Drive came keyed for Both B+M, and thought it wouldn't be compatible, but this article helped a ton!

Posted on 2016-08-15 15:12:47
Avatar Trent Watson

M.2 2280 PCI-Express 3.0 x4 Internal SSD backwards compatable with PCI-Express 2.0 x4

Posted on 2016-09-23 05:11:38
Avatar Trent Watson

that is can i put an m2 2280 3.0 x4 on my predator HLHH 2.0x4 adapter and get it to run ... should not get full speed of the 3.0 but still work at 2.0 speeds ?

Posted on 2016-09-23 05:13:30
Avatar Trent Watson

i get 1330 reads & 768 writes now on my ssd ...... so with the newer m2 pci 3.0 x 4 the speed goes up to 2500 reads and 1300 writes however the 2.0 lane could theoretically reach 1500 read and about 1000 write with a 3.0 m2 ssd as long as it is really backwards compatable .. also the m2 3.0x4 ssd's are cheaper that the m2 2.0 x4 so I could get a 960gb ssd for around 300 bucks and it would be smoking fast even in m old pc ... right now it is super fast with the older m2 2.0 x4 on the predator BUT thats only a 256 gb drive m2 2.0 x 4 if i could get the writes and reads bumped up another 20% or so and get the 960 gb capacity then it would be pretty awesome ..... anyone tech savy have anyfeedback ????

Posted on 2016-09-23 05:20:11
Avatar Peter John

Great information - thank you.

I found an error:
What is interesting to see is that a M.2 drive using PCI-E 2.0 x2 only has a 25% potential speed increase over SATA III.
Your math is off:
SATA III 6.0 Gb/s (750 MB/s) ---> PCI-E 2.0 x2 8 Gb/s (1 GB/s) = 33% increase - not a 25% increase.

Posted on 2016-10-05 12:03:46

Thanks, I got that fixed!

Posted on 2016-10-05 17:03:32
Avatar Zachary

I have a Toshiba Z30-c1320 that came with a B+M keyed sata M.2 ssd. Would it be possible to upgrade to a PCI-E based SSD, and would a M connector work on a B+M board? Thanks in advance.

Posted on 2016-11-13 17:12:34
Avatar left shin

The image used to describe the keys is incorrect. You'll notice that the B key has 6 pins but is shown on the right instead of the left like in the picture of the actual SSD. There is a mock up of how the image should look on wikiwand in the M.2 article. I've also reposted on an image host for simplicity. http://imgur.com/a/PQZNM

Posted on 2016-12-04 09:17:48
Avatar Jakob Hviid

Hmm thx for the info..(are little uncertain, since I couldnt get my new M.2 256GB drive intel P600 to fit in my (USB3 M.2 NGFF memorystick) it looks like it would fit from close to identical pin placement, if you turn it around, but there is like an mm of an edge so very tight and dont wanne temp my faith.

But after reading up on the net and your info here and the pictures, i can conclude there is two plug versions for m.2 there is the Bkey and the M-key, and would reckon this P600 Intel is Mkey and the usb3 stickdrive says Bkey.(but damn these pins look much a like, if you just turn it up side down.)

Is my presumption correct, that there is no chance that an Mkey SSD would work in a bkey plug ewen thow you would fit it with some pressure and the pins where align, and more likely my new SSD m.2 card decide to share a cigarette with me with some magic smoke.

bummer if the Bkey plug cant be used for an 2280 P600SSD-card, will see if i can optain an M-key adapter for secondary-use ewen thow it will limited it (purchase the drive along with black friday offers here in DK)

Posted on 2016-12-06 23:01:59
Avatar Jakob Hviid

Hmm. Im starting to get the impression that M'key-plug-format aint compatible at all for either USB3 adapters or sata adapters, only plain pin PCI 4x interface, while B-key M.2 is compatible both for sata and USB3 since there is an bunch of cheap sata or USB3 m.2 Bkey-adapters, lurking around.

can it be due to the 4x M-key standard' hence 2x on B-key M.2 formats, but aint these useally backcompatible, like 4x also is open for 2x that seems to be in play for the B-key formats.

// seems there is a classification and a standard also being called B+M Key cards, aka cards with holes in both ends, seems to go under the title gen2 M.2 sockets, while the above Intel P600card i took the plunge on at cheap sale, is gen3 and solely M-key. (if gen3 sockets is only able to be put in PCI-pins socket and doesnt is open now, or in the future for SATA or USB3,.. that I dont know?)

seems there s also an dedicated M.2 sata SSD formats, if that is gen1 M.2, dont know.

Posted on 2016-12-07 23:48:50
Avatar James Scott

Your speed comparison chart is a bit off for PCI express. The speeds that you list as the theoretical max is actually the real speed. PCI Express 2.0 lanes operate at 5 Gt/s, so 5,000,000,000, now consider that PCI express uses 8b/10b encoding, which means you lose 20% of bandwidth to overhead. You would get a formula like this 5,000,000,000 * 0.80 = 4,000,000,000 bits/s / 8 = 500,000,000 bytes/s * 2 lanes = 1,000,000,000 bytes/s = 1GB/s of throughput in the real world. A x4 lane would be 2GB/s. This yields a 66.6% increase in bandwidth from SATA 3 to M.2 using PCI Express 2.0 with 2 lanes. Which would mean a PCI Express 2.0 with 4 lanes yields a 333.33% increase. PCI Express 3.0 operates at 8 Gt/s, and uses 128b/130b. So 8,000,000,000 * 0.9846 = 7,876,800,000 bits/s /8 = 984,600,000 bytes/s * 4 lanes = 3,938,400,000 bytes = 3.9 GB/s, which you have correct.

Posted on 2017-04-28 17:46:11
Avatar j.b

Thanks for this information. I had no idea about these different keys and dimensions.

Posted on 2018-02-13 23:27:51
Avatar BGM Coder

Where can I get an adapter or chip reader or anything so I can connect my m.2 m-key ssd to my computer externally? I've searched the world over...

Posted on 2018-02-24 20:10:48
Avatar Sajid Maqsood

i agree. picture is wrong. it is fliped. 'M" key cut is on right side on socket and 'B' key cut is on left on socket. please correct this picture.

Posted on 2018-12-22 22:30:31
Avatar Richard Sayer

This article is a wealth of information in one location, needs a 2020 update! Thank you.

Posted on 2020-11-11 20:26:03