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.