Samsung SM951 PCIe M.2 512GB SSD Review

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Final Thoughts

The SSD market will change in 2015. Marvell, SandForce (now part of Seagate), Phison and JMicron will release PCIe-based controllers around June, just in time for Computex. We expect Intel to release the HHHL 750-series SSD, the company's first consumer PCIe-based SSD, any time now. At least two vendors will even break the PCIe market into two categories, performance and value, similar to the 2.5" SATA SSDs today. The dividing line will be the number of PCIe lanes utilized. Expect value-oriented products to sit on two lanes, while high-end offerings exploit four.

Samsung's SM951 ascends the throne in that latter category as the fastest consumer SSD you can buy. How long it holds the title remains to be seen. Not only are other companies working to take the crown, but Samsung's retail arm might have a solution of its own.

Samsung chose to release this product to OEMs with 16nm 2D planar flash, a cost-cutting measure. System builders work hard to keep costs low at the component level, and 3D V-NAND would have been counterproductive on an already expensive device. We expect Samsung to take advantage of its PCIe development advantage and deliver a retail product aimed at enthusiasts with second- or third-generation 3D V-NAND. The SM951 press release alluded to an upcoming NVMe-based offering later in 2015. We found that little quip extremely odd; it was almost like a warning to early adopters.

Until Samsung announces a PCIe-based M.2 SSD for the retail market, we'll have to keep searching out hard-to-get gems like the XP941 and SM951, which ride a fine line between the retail and gray markets. Sadly, that means these specialty products cost more than other premium SSDs made in larger quantities. You'll also have a difficult time finding them for sale.

Most new premium motherboards already support M.2 PCIe SSDs. On those that don't, you can use a M.2-to-PCIe adapter, just like plugging in a video card. The adapters are passive; just be sure to get the right model built for PCIe M.2 products. Notebook support is more complicated. The Lenovo X1 Carbon Gen 3 supports the SM951, as does at least one Dell model that is shipping today. Several companies plan to launch notebooks with support for four-lane M.2 drives, and some of those won't even accommodate 2.5" SATA storage devices. Undoubtedly, this will increase M.2 market share.

At this time, Samsung's SM951 is the fastest M.2 product you can buy. Not only is it quicker than existing PCIe-based M.2 drives, but it also delivers performance that compares to all-in-one RAID products like OCZ's RevoDrive and G.Skill's Phoenix Blade. Our testing didn't uncover any weak links in performance. Generally, it's difficult for a company to develop a SSD that doesn't have a flaw somewhere. But Samsung's new UBX controller manages to fix the XP941's weak mixed-workload performance and heat issues under random write workloads. The SM951 runs much cooler, so it won't be a problem running the drive on your motherboard with a video card close by.

The SM951 512GB is the best consumer SSD money can buy. We just wish Samsung would release a 1TB version and improve availability.

Chris Ramseyer
Chris Ramseyer is a Contributing Editor for Tom's Hardware US. He tests and reviews consumer storage.
  • blackmagnum
    This is an awesome upgrade for some Macbook Air/Pro users, but just wait until Intel shows their product... and will there be any hardware compatibility issues with DIY upgrades?
  • Sakkura
    I'm disappointed the promised NVMe support did not materialize. But I guess Samsung is saving that for later retail products. Can't argue with the performance though, this is by far the fastest consumer SSD around.
  • Memory Ever
    May I know the model and nae of the PCIe adapter you used in the tests???
    No 1TB edition? Fail.
  • tom10167
    I wish they'd put an 840 or 850 pro in the comparison just to give us a better sense of scale. This drive is incredible, though, and $550 for a 512GB cutting edge drive is not terrible!
  • mapesdhs
    The Power Restricted Performance graph is stupid. Please stopping using
    graphs with origins that don't start at zero - the visual graphic impact is
    totally meaningless.


  • jeffunit
    You might want to fix the labels of your graphs. Latency in seconds? One chart shows a write speed of about 80 gigabytes per second.
  • liquidpower
    I also wished they put a 850 pro in the charts to see the jump from the fastest sata to the PCIe-based M.2
  • maestro0428
    You can purchase these at in the Enterprise SSD section. I want one!
  • generalsheep
    Is this little bastard bootable,so i can use it as my maindrive?