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


The SSD Review uses benchmark software called PCMark Vantage x64 HDD Suite to create testing scenarios that might be used in the typical user experience. There are eight tests in all and the tests performed record the speed of data movement in MB/s to which they are then given a numerical score after all of the tests are complete. The simulations are as follows:

  • Windows Defender In Use
  • Streaming Data from storage in games such as Alan Wake which allows for massive worlds and riveting non-stop action
  • Importing digital photos into Windows Photo Gallery
  • Starting the Vista Operating System
  • Home Video editing with Movie Maker which can be very time consuming
  • Media Center which can handle video recording, time shifting and streaming from Windows media center to an extender such as Xbox
  • Cataloging a music library
  • Starting applications


In PCMark Vantage the 512GB Samsung SM951 achieved a Total Score of 173,260 points. This is the second highest we have seen out of a single SSD in this system, second only to the Intel 750. A majority of results are well above the SATA 6Gb/s barrier with the highest transfer speed of 1,522MB/s was recorded during the “Windows Media Center” benchmark. The lowest of 265MB/s was recorded during the “application loading” benchmark. Let’s continue on to our PCMark 8 test and see how it fares there.

Samsung SM951 512GB AHCI PCMark Vantage



For our last benchmark, we have decided to use PCMark 8 Extended Storage Workload in order to determine steady state throughput of the SSD. This software is the longest in our battery of tests and takes just under 18 hours per SSD. As this is a specialized component of PCMark 8 Professional, its final result is void of any colorful graphs or charts typical of the normal online results and deciphering the resulting excel file into an easily understood result takes several more hours.

There are 18 phases of testing throughout the entire run, 8 runs of the Degradation Phase, 5 runs of the Steady State Phase and 5 runs of the Recovery Phase. In each phase, several performance tests are run of 10 different software programs; Adobe After Effects, Illustrator, InDesign, Photoshop Heavy and Photoshop Light, Microsoft Excel, PowerPoint and Word, as well as Battlefield 3 and World of Warcraft to cover the gaming element.

  • PRECONDITIONING -The entire SSD is filled twice sequentially with random data of a 128KB file size. The second run accounts for overprovisioning that would have escaped the first;
  • DEGRADATION PHASE – The SSD is hit with random writes of between 4KB and 1MB for 10 minutes and then a single pass performance test is done of each application. The cycle is repeated 8 times, and with each time, the duration of random writes increases by 5 minutes;
  • STEADY STATE PHASE – The drive is hit with random writes of between 4KB and 1MB for 45 minutes before each application is put through a performance test. This process is repeated 5 times;
  • RECOVERY PHASE – The SSD is allowed to idle for 5 minutes before and between performance tests of all applications. This is repeated 5 times which accounts for garbage collection; and
  • CLEANUP – The entire SSD is written with zero data at a write size of 128KB

In reading the results, the Degrade and Steady State phases represent heavy workload testing while the recovery phase represents typical consumer light workload testing.


As you can see, performance is recorded in terms of Bandwidth and Latency. Bandwidth (or throughput) represents the total throughput the drive is able to sustain during the tests during each phase. Latency, at least for the purposes of PCMark 8, takes on a different outlook and for this, we will term it ‘Total Storage Latency’. Typically, latency has been addressed as the time it takes for a command to be executed, or rather, the time from when the last command completed to the time that the next command started. This is shown below as ‘Average Latency’.

PCMark 8 provides a slightly different measurement, however, that we are terming as ‘Total Storage Latency’. This is represented as being the period from the time the last command was completed, until the time it took to complete the next task; the difference of course being that the execution of that task is included in ‘Total Storage Latency’. For both latency graphs, the same still exists where the lower the latency, the faster the responsiveness of the system will be. While both latency charts look very similar, the scale puts into perspective how just a few milliseconds can increase the length of time to complete multiple workloads.

For a more in-depth look into Latency, Bandwidth, and IOPS check out our primer article on them here.


These results show the total average bandwidth across all tests in the 18 phases. In this graph the higher the result the better.

Samsung SM951 AHCI 512GB PCMark 8 Average Bandwidth


These results show the average access time during the workloads across all tests in the 18 phases. In this graph the lower the result the better.

Samsung SM951 AHCI 512GB PCMark 8 Average Latency


These results show the total access time across all tests in the 18 phases. In this graph the lower the result the better.

Samsung SM951 AHCI 512GB PCMark 8 Total Latency

In our consistency testing with PCMark 8 the Samsung SM951 shows off the highest average bandwidth yet, surpassing even the Intel 750. Overall, consistency is very good with almost no fluctuation throughout each phase. When it comes to latency, however, there is a bit of a tradeoff. While we see some of the best bandwidth yet, its latency is not as low as the Intel 750 and a bit higher than the previous XP941. Still, with an average of 0.05ms during the heavy workload phase and 0.04ms during the light workload phase is quite impressive.


  1. 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?

    • 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.

      • 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.

      • 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?

      • 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

  2. Whydoyoucloseyoureyes

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

    • 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.

      • Whydoyoucloseyoureyes

        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.

      • 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.

      • 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!

    • 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.

      • Whydoyoucloseyoureyes

        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?

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

    • 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:

  3. Hi Les,

    Thanks for the review.

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

  4. allesichmacheichmacheesfurmich

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

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

    • The AHCI version would be yes.

      • 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!

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

      • 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?)


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

      • 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!

      • SM951 AHCI I mean

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

  6. 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.

  7. 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?


  8. 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.

    • 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.

      • 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.

  9. 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..

  10. 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…

Leave a Reply