Thursday , 23 October 2014
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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.

HHHL

WHERE DID THE NAME M.2 COME FROM?

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:

Connectors

UNDERSTANDING M.2 SSD KEYING

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.

Capture

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:

About Les Tokar

is a technology nut and Founder of The SSD Review. His early work includes the first consumer SSD review along with MS Vista, Win 7 and SSD Optimization Guides. Les is fortunate to, not only evaluate and provide opinion on consumer and enterprise solid state storage but also, travel the world in search of new technologies and great friendships. Google+
  • Rod Bland

    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…

    • http://thessdreview.com Les@TheSSDReview

      Rod…a big thanks to you for setting our M.2 SSD reporting in motion. Huge kudos my friend.

      • Rod Bland

        No problems Les. I’m just waiting for an invite to one of these summit junkets you are always going to. Make some room in a suitcase and I’m there! ;)

      • renosablast

        The folks at LSI were certainly top-notch hosts.

  • Tim

    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. http://www.pcisig.com/specifications/pciexpress/M.2_Specification/

    • http://thessdreview.com Les@TheSSDReview

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

      • tim

        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.

      • http://thessdreview.com Les@TheSSDReview

        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.

  • Smitty

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

    • http://thessdreview.com Les@TheSSDReview

      Yes same combo card that we reviewed the ADATA on…

      • Smitty

        Been a couple days… what was the surprise?

  • Pawe? Miciak

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

    • http://thessdreview.com Les@TheSSDReview

      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.

      • Pawe? Miciak

        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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