Samsung SM951 M.2 PCIe SSD Review (512GB)

In 2013 we were able to get a hold of Samsung’s first go at an OEM M.2 PCIe 2.0 x4 SSD, the XP941. Once word got out about this SSD’s speeds many storage enthusiasts thirsted for it. Samsung was not prepared for the consumer market to get so hyped up over it and they stopped distribution to 3rd party resellers as demand was exceeding supply. After a few long months it was finally available again and if you were big on fast storage, this small gum stick SSD was the one for you.

Now, fast forward to 2015. A few weeks ago we took a look at a very fast consumer M.2 SSD, the Kingston HyperX Predator. It offers consumers great speeds as well as endurance, surpassing that of the XP941. Not only that, but it is easily bootable in almost any system. Now, it claims the title of the fastest consumer M.2 PCIe SSD out, however, it isn’t the fastest M.2 option to the storage enthusiast.

Samsung SM951 AHCI M.2 PCIe 512GB Main

Today we are going to take a look at Samsung’s SM951, an OEM M.2 PCIe 3.0 x4 SSD that offers speeds of up to 2.2GB/s read and 1.5GB/s write! These speeds are almost in line with what the much larger HHHL Intel 750 can do and yet it does this in a M.2 2280 form factor with only a few NAND packages!

One important thing to note is that the SM951 comes in two different SKUs, one denoting the AHCI variant (P/N: MZHPV) and the other denoting the NVMe variant (P/N: MZVPV). In this review we are taking a closer look at the AHCI variant. We know many of you are interested in the NVMe unit and we are in the process of securing one for review now that they are in production. Believe us, we will post up a review of that unit as soon as we get a hold of one.


The Samsung SM951 is currently available in three capacities, 128GB, 256GB, and 512GB. In terms of speeds, the 128GB can provide up to 2,050MB/s read and 600MB/s write, the 256GB model 2,150MB/s read and 1,200MB/s write, and the 512GB model 2,150MB/s read and 1,500MB/s write. Random IOPS across all models are rated for up to 90K IOPS read and 70K IOPS write. The SM951 supports APM and an L1.2 Power Saving Mode. Active power consumption is rated at 6.5W while the normal active standby mode consumes just 50mW of power at idle, but the L1.2 mode allows the SM951 to consume just 2mW! That is the same amount as DevSleep, but can fully power up at a much faster rate! It also supports End-to-End Data Protection, TRIM, and is RoHS and Halogen-Free Compliant. The endurance for the 128GB and 256GB models is rated at 75TBW while the 512GB model is rated for 150TBW.

While the SM951 is not available as a retail SSD, it is available through third party vendors such as RamCity and Amazon. After taking a look, the current prices on Amazon, the 128GB model is $169.99, the 256GB model is $244.99, and the 512GB model is $494.99. In terms of warranty, since it is not a retail product, it depends what the reseller offers. RamCity and Amazon offer 3-year warranties. RamCity has a warning on their website stating that if you secure erase your SSD, the warranty becomes void as some have bricked their SM951s doing so.


Bootability is going to be the main issue if you are looking into buying one of these. While Z97 and X99 will most likely be able to boot off this SSD, it depends on the motherboard manufacturer to provide a compatible UEFI. Older chipsets will most likely not work save for some Z87 motherboards. If you are interested you should even check out a great post RamCity has on their website with many compatible motherboards listed.

In order for us to boot off of the Samsung SM951 we had to update the UEFI for our ASRock Z97 Extreme6 to P2.10 from P1.70. After installing windows we saw boot times at about 7-8 seconds with Ultra Fast Boot enabled from powered off to desktop, the monitor didn’t have enough time to turn on so it was kind of hard to get an accurate measurement. So it is fair to say, if you have a compatible motherboard, you can get some very fast boot times with this SSD. For comparison our Samsung 850 Pro boots up in about 8-9 seconds from powered off to desktop.


As an OEM product, there is no standard packaging for consumers to look at, all they get is the SSD itself, a trade off one will have to take for this type of performance.

Samsung SM951 AHCI M.2 PCIe 512GB Front

The front of the 512GB PCB contains a single controller, DRAM chip, and two NAND packages and the backside contains two more. The overall weight of the SM951 is just 6g.

Samsung SM951 AHCI M.2 PCIe 512GB PCB Front Samsung SM951 AHCI M.2 PCIe 512GB Back

We can see that the M.2 connector is an M key, thus showing this is a PCIe only SSD. If you want to use this you need to make sure that you have the proper M.2 to PCIe adapter for it as M.2 to SATA adapters will not work.

The Samsung UBX 3-Core controller paired with their 16nm MLC power the SM951’s speeds up to 2.2GB/s. 

Each NAND package is 128GB in capacity for a total raw capacity of 512GB, once formatted the end user has 476GB available to them.  Both the 256GB and 512GB models utilize a 512MB LPDDR2 DRAM buffer while the 128GB utilizes a 256MB LPDDR2 DRAM chip.


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    How does Samsung consistently end up on top of all other ssds? You have all these major players, Intel , Crucial , Toshiba , SanDisk. Every now and then someone gives them a challenge, but they seem to always end up back on top. Is it there controller, nand, firmware, controller/nand, what?
    And if you raid 0 two sata SanDisk extreme pros can you get
    the same consistency bandwidth as one of these m2 drives?

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      Samsung is a marketing Goliath. Because they are the largest tech company in the world (selling 4 cell phones and 2 TVs every second of the day), they have the resources to sink into their products. People buy Samsung SSDs just for the name because they recognize that name and trust it. Don’t get me wrong; the other companies are giants in their own right and, given the right marketing tactics, could compete with Samsung. They just aren’t there yet…or maybe they just haven’t made that right step.

      Want an example? Intel is the worlds top CPU. Could they not have made a CPU/SSD combo years ago when SSDs were on the rise…or even a CPU with great SSD discount coupon? I could go on forever with respect to selling flash…it is such an easy sell with just the right approach. Last but not least…look at Samsung’s release history and notice how well times everything always seems to be.

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        Thanks that was a very good explanation. But what about the second question? If you raid 0 two sata SanDisk extreme pros can you get
        the same consistency bandwidth as one of these m2 drives? The SanDisk had half bandwidth 200-250, so times 2 400-450 could it compete. I only ask because I have a old motherboard with no more pcie slots.

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        No the SanDisk RAID would not come close. Even with 100% incompressible data, this drive transfers data at speeds of 1.9GB/s read, 1.5GB/s write and 175K IOPS. This SSD is a blessing for those working in 4K media where a minimum of 1.4GB/s is necessary. I always speak of the importance of understanding ones need however and, with that, matching the right SSD with the task at hand. Does the typical PC user need this or will they ever understand its abilities? Absolutely not…but it is still sweet though isn’t it?

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        Diego Valenzuela Ossa

        today samsung evo 850 is technically the best deal for price and quality. and probably going for this SM951 card next year. my choice to buy the model I had wasn’t actually based on the brand name

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    not a single review site has tested boot times with this disk. not one!!!

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      Boot times differ for the most part by seconds and cannot be measured accurately as each system is different. The importance of boot times is seen between the hard drive and the SSD. To compare SSD boot times is a defeating task as the boot time, for the most part, is based on disk access times for which most SSDs are a fraction of a ms different.

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        thank you for the feedback! but there are cases where boot time tested on a specific motherboard can reveal quite a difference, for instance the intel 750 ssd has the slowest boot time of any high end ssd, while the sm951 supposedly has the absolute fastest of all consumer ssds. like several seconds difference actually.

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        I understand your point and appreciate the work that my friends at TechReport do. I have had every one of those SSDs in use in one system or another in one point in time or another and I have never experienced a 30 second boot. In fact, my system optimization is always the same and my start times are typically 15-20 seconds when fully optimized with our SSD Optimization Guide. There are VAST differences in boards and, as such, a significant start time difference will be experienced between newer NVME compatible boards and those of just yesterday that relied on Win 8.1 NVMe drivers alone. Similarly, to put a notebook SAta SSD, beside a PCIe 4 lane and then NVME, a few seconds difference can be expected. I understand your initial concern but, the way I have always looked at presenting SSDs to the consumer (and enterprise), I prefer to stay away from comparisons where the results of drives are really not that tangible in my opinion. The best part of it all is that there are several websites for comparison, or different benchmark characteristics to draw upon.

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        It would be interesting to understand a bit more about this variability in boot time. Dust off the ol’ SAS program and collect a large amount of data and get real nerdy with it!

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      I did, I booted off this SSD in about 7-8 seconds as stated under the bootability section in the review on the first page. The Intel 750 booted similarly as other SSDs as well when I had it.

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        i had the 750, it booted real slow, like stupid slow compared to my old 120gb corsair. i have the 850 pro now and its insane compared to the 750.

        Also i could not install hackintosh on my 750 which sucks , but hackintosh does have sm951 support 🙂

        I also have the asrock extreme6 so i can buy the sm951 and use it if i needed, but tbh the 850 pro in daily usage is just as fast. and the sm951 has throttling issues. try placing a fan over it and see if performance increase?

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      booted in 10 sec (i5+DDR 1600 Mhz+sm951 AHCI)

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      I posted my 2nd boot on Youtube the day I received the drive… sorry the video quality on my phone sucks, but you can see how long it takes!

      If you want to see even faster Samsung drives in a 4-way mirror (2 column, 2 copy in Storage Spaces), look at my last post here… fastest SSD config I’ve ever seen:

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    Hi Les,

    Thanks for the review.

    If you’re interested, there’s a newer version of AS-SSD (v1.8.5608.42992).

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    What is the issue with this thing that potentially bricks it with a secure erase?

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    I would like to upgrade my Vaio pro 13 pcie SSD samsung xp941 to the new sm951 would this be compatible?

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      The AHCI version would be yes.

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        Muthukumar Natarajan

        Is this tested? Especially, does the SONY VAIO Pro 13 boot from SM951 (512GB)? Could you please point to anywhere wherein someone has it actually tested and the result available?
        I know, technically it should work, but don’t want to take a chance while I buy.
        Many Thanks!

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        Of course it will work but I would go for the newest 950 pro now.

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        Muthukumar Natarajan

        Sorry, I too know that technically it should work, but I was more looking for actual experience, especially regarding whether it Boots.

        Also, regarding the 950 Pro, I know it is based on NVMe, whereas the SONY VAIO Pro supports only AHCI as far as I know. So when you recommend 950 Pro for SONY VAIO Pro, how is it going to work?:
        1. By itself? (I wonder how) _OR_
        2. Any BIOS Update available for SONY VAIO Pro for NVMe support? _OR_
        3. Is 950 Pro by any chance backward compatible with AHCI (again, Bootable?)


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        Woops my apologies; 950 pro will not work and the SM951 (AHCI version) will.

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        SM951 will not work in Pro13 people don’t waste your time and money like me. XP941 is best you can get for Pro 13 tried both in my Pro 13 other people having same problem with SM951 won’t work as bootable partition!

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        SM951 AHCI I mean

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        Why the SM951 AHCI not works in the vaio pro13 ? thanks.

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    Question, what kind of a speed decrease can you expect to see on this drive if you use it on a PCIe Gen2 x4 slot instead of Gen3? My laptop only has a Gen2 x4, so am curious what kind of decrease I should expect from this ssd.

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    Christopher Caruk

    Hello, I’m currently testing the 512GB AHCI and NVMe versions of the 951 on the PCIe 3.0 bus on an ASUS Z97i-plus. The NVMe is able to achieve the read speeds that you posted but I’m seeing a maximum of around 1100MB/s read speed on the AHCI variant. See comments here for more information:

    Could this be a limitation of the board or a misconfiguration of the PCI bus?


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    Thanks for the review! However, I’m not really seeing the value add here, particularly for the money they want, over a standard SATA SSD.

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      It is application specific my friend; what are your needs? The average user won’t see any difference whatsoever between the two drives, however, this becomes gold to a media professional. Faster transfer speeds means higher efficiency which means more work done and coin in the pocket/time for the family.

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        By all means, that makes a lot of sense. I’m just surprised from an enthusiast or consumer perspective since many motherboard manufacturers are now including M.2 slots into their socket 1151 motherboards. Guess I’ll hold off for another year or two.

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    Just bought SM951 512gb AHCI to upgrade my Vaio Pro 13 but for some reason I can’t create partition when installing windows7 it gets stuck at partition screen the partition is there but windows won’t load on it. Just strange because before that I had SATA SSD AHCI. What I am missing? Tried Different Bios settings but no luck..

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    Happy owner of a Lenovo Y700 17ISK (ideapad) that has this little beast inside set up as disk 1.
    Installation of windows 7 64 bit possible only when installing on 1Terra Western Digital disk 0 and then cloning with another program from inside windows to disk 1.
    But if partitioned as GUID (GPT) SATA AHCI boot and NTFS this little baby can really bring some difference to Windows experience even on an old OS…
    Counted from Lenovo screen on bootup till CTRL-ALT-DELTE screen only 6 seconds (most of which came from the Windows visual effects on Windows start up screen). Without effects it would need 2 or 3 seconds to get there… (Windows 2003 Server Domain login…)
    As for its use, Word in half a second, Mozilla in 1,5 seconds, outlook less than one second. I repeat Domain environment)… Forgot to mention ESET 64 bit with file protection activated… Blindingly fast disk if supported by system…

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