Understanding M.2 NGFF SSD Standardization (Or The Lack Of)

So I am a few thousand miles above beautiful California and the 2013 LSI Accelerating Innovations Summit. I can’t help but reflect on the confusion that still exists concerning the standardization of M.2 SSDs, regardless of how many times we try to explain this in our reports (1, 2, 3).  If you are confused and not an industry professional, don’t be embarrassed. Many storage insiders are just as confused and also realizing that there really is no standardization with M.2 SSDs.

NGFF M.2 SSD Image 1

To compound things, there were no PCIe X4 M.2 SSDs on display at the AIS, and with good reason, according to the SandForce Marketing Team. While everyone at the show might have expected LSI to build and show a PCIe x4 M.2, it looks like they are initially focused on the larger majority of PCIe x2 M.2 systems out now. The standard PCIe x4 HHHL board they did show certainly proved the SF3700 can hit the PCIe bus 1800 MB/s limit.



Some time ago, the Gods responsible for SSD standardization realized that there were just too many small form factor SSD types.  In their wisdom, they decided to take a crack at standardizing future PC systems by incorporating a standard connection, called a M.2 connector (or host).  Initially, they didn’t want to give an SSD the name of a connector, so the name NGFF was born, meaning ‘Next Generation Form Factor’.  A bit amusing perhaps is the fact that, even today, NGFF remains to be a more recognizable name than M.2 itself , and also provides much more specific results when doing a Google search.

M2 Connector

As much as so many of us would love the M.2 host to be the ‘holy grail’ of SSD standardization, it’s not.  It is a connector, and a female one at that.   It is not restricted to SSD use alone, and can also be utilized for Wi-Fi, WWAN, Bluetooth, GPS, NFC, as well as several interfaces to include PCIe and SATA.  A key point here is that PCIe and SATA are different interfaces and one cannot be reached via the other, meaning, these SSDs cannot be simply switched off in M.2 capable systems. As we are learning, the only REAL standardization is the connector itself.  The male connector on the SSD is not standardized and can be either of the two shown here:



This picture depicts two SSDs, the Samsung XP941 native PCIe SSD (reviewed), which operates at a theoretical high of 1.4GB/s, and Toshiba’s first M.2 SSD release (also reviewed), which is a SATA 3 SSD and will hit typical 6Gbps highs of 575MB/s.  You will notice that the connector of the Samsung SSD has one notch separating two sets of contacts; this is termed the ‘M’ key.  Similarly, the Toshiba has two notches and these are known as the ‘M’ and ‘B’ keys, just as you see in this PCIe Gen 2 X2/SATA 6 Gb/s 80mm M.2 SSD featuring the new SF3700 flash controller.

LSI Display

Only the single ‘M’ keyed SSD can reach those lightning fast speeds that we have seen in the Samsung XP941, and will be evident in SSDs containing the LSI SandForce SF3700 flash controller. This is because only the single ‘M’ keyed connector connects by PCIe X4.  A single ‘M’ Keyed connector can also be used for SATA, but that would make as much sense as throwing the body of a Ferrari on a Ford Focus.

To carry this a bit further for those relatively new to data travel, PCIe Ver. 2.0 is capable of a maximum transmission rate of approximately 500MB/s per lane.  Four lanes (X4) enables speeds up to 2GB/s (4x500MB/s) as we might see in the Samsung XP941 and LSI SandForce SSDs.  PCIe 2.0 X2 will allow speeds up to 1GB/s (2x500MB/s) and we will soon see this first hand with the Plextor M.2 PCIe X2 SSD, named the M6e.


This picture illustrates the new LSI 3700 flash controller on a PCIe 2.0 X4 M.2 SSD, for the first time, and we felt it important that the reader see both together. This combination is the only that will enable lightning fast 1.8GB/s speeds from an M.2, and subsequently, the smallest and fastest SSD in the world.  A click on this picture will display it in a higher resolution and, as well, this video might explain why the SF3700 just may be groundbreaking entry into the SSD arena:


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    Thanks for the detailed explanation Les. I must admit, it’s a lot clearer this time around even though I know you’ve explained the same several times before. Hope that leg is back to 100% soon…

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    There is a standardization of all aspects, from the keying to the sizes of all the boards involved. The standardization specification can be found here. https://www.pcisig.com/specifications/pciexpress/M.2_Specification/

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      Thanks Tim! We weighed the inclusion of just that link and then decided aghainst it for simplicity sake.

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        Well, it is an article that states there is no standardization, yet there is a published specification that covers every single aspect of the standard, literally down to the millimeter. One would think this would be relevant.

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        I’ll go there wih ya if you like. There is absolutely nothing wrng with the specification and you are completely correct in your statement that it is very thorough. Other than the fact that the pdf is NOT available for public download, the difficulty with the final product is that it is either too confusing for even industry professinals to understand….or to mundane to even reach specific passages without complete boredom. If it were, we wouldn’t even be commenting on such an article would we now.

        Likewise if the spec were so clear, perhaps people wouldn’t be receiving SATA 3 M.2 systems when they paid for PCIe M.2 SSD systems which were advertised as just that. Again thanks for your input.

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    Desperate to find a M.2 SSD readily available in the USA that is larger than 120GB for my ASUS Impact mITX motherboard.

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    Can I use SSD M.2 M and B notch with the slot which has only M notch?

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      Can you give a more specific example? M.2 connectors only have the single slot but it is much more than that. We need to see how it is connected to the board. For instance, a M.2 PCIe may fit into the connector but the base system might not word because it is set up for SATA M.2’s.

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        I would add to my Lenovo Y510P ssd drive. There is a M.2 slot, exactly as on the 3rd picture this article. The qestion is: Will it work with SSD which has M and B notch? I would move system to SSD drive and keep standard 1TB HD.

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    I am using HP Spectre ultrabook 3010dx and would like to upgrade the SSD, unfortunately its having only M notch and in HP website mentioned that it is Msata SSD(M.2 config), Could you please give me a suggestion.

    Thanks in advance

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    “few thousand miles above beautiful California” – is it ISS you are writing from?

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    @TheSSDReview:disqus I currently have a Sony Vaio Pro 13.

    SATA III M.2 SSD Samsung MZNTE128HMGR-000SO is installed inside. Now Im considering whether to buy 256gb ssd or 512 one. I think i found first variant.

    However, im very interested which *512gb ssd* will be suitable in my case?

    As i figured out, this one might do the trick https://www.amazon.com/Samsung-512GB-PM851-MZ-NTE5120-MZNTE512HMJH-00H1/dp/B01A855VWS/ref=sr_1_1?s=pc&ie=UTF8&qid=1458174865&sr=1-1&keywords=mznte512hmjh

    What do you think? Is there a possibility, that BIOS drivers won’t recognize it?

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    I am still confused after reading the article.. mostly about the M and B notch. The picture is not clear and should be labeled “Image 1”, “Image 2”, etc.

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    No wonder I’ve seen so many “M.2 SSDs” so cheap lately. They are ‘SATA’ ssds (they have both notches in their connectors, [A and M]), and yield no faster speeds than a typical god’ol SSD connected to the typical SATA 6Gbps connector!
    Still, a 128GB ‘M.2 SSD’ for under $50.00 is a good bargain!

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