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


The previous XP941 was notorious for reaching very high temperatures when under heavy workloads. In order to test out the SM951 to see if it did as well we used Iometer. We set 128KB seq. read and write workloads at QD32 to get the most heat and speed possible out of the drive over a 10 minute span, displayed are the speeds every second (600 points). With a temperature probe we recorded the temperature of the controller every 30 seconds over the 10 minutes.

Samsung SM951 512GB Temp vs Throughput

As we can see, the SM951 512GB model reached a max of 81C in our test bench. This temperature was achieved after about 2 minutes. To put that into perspective, writes transferring at full speed over 2 minutes equates to about 180GB. When looking at the read side of things it isn’t until about 5 minutes in that it hits 80C. At that point it had already read about 675GB of data, more than the capacity of this SSD. We can see that after the 2 minute mark that read speeds have some temporary drops down to about 75MB/s due to thermal throttling. Since you are unlikely to do continuous transfers of this magnitude all the time, it shouldn’t be something to worry about, however, in case you are, you may want to look into putting a small heat sink on it the controller or placing a fan near it. With a 120mm fan pointed at it, max temps hit only 61C.


The performance delivered by the Samsung SM951 M.2 PCIe 3.0 x4 SSD is very impressive to say the least. Throughout our testing we seen read speeds as high as 2,260MB/s and writes as high as 1,600MB/s, exceeding that of the manufacturers rating. In terms of IOPS we saw much better results, read IOPS were double that of its rating reaching 180K, while write reached about 100K IOPS with Iometer. We can see that as an OEM SSD we can see that it has been optimized for client usage. In PCMark Vantage this model hit a total score of over 170K points with half the speeds clocking in over 1GB/s! Continuing the trend we seen the highest bandwidth performance in PCMark 8 yet, surpassing that of even the Intel 750. Latency was very consistent and low overall averaging 0.04 – 0.05ms, much better than that of many SATA SSDs in the market.

Now, with such fast performance usually comes high heat output, however, when compared to the XP941, things have improved. During our torture testing of full sequential transfers via Iometer we seen a max temp of 81C. It wasn’t until about 2 minutes in we started to see some thermal throttling down to about 75MB/s, however, bear in mind that it equates to transferring 180GB at full speed. Due to this being untypical of most users workloads, we would have to say that thermal throttling isn’t something you will normally running into and should not be of concern.

Samsung SM951 AHCI M.2 PCIe 512GB Controller

Overall, we are quite pleased with the Samsung SM951. With the combination of Samsung’s UBX controller and their 16nm MLC NAND it delivers best in class performance. We can easily see many who are into amateur multimedia production using this SSD. Having a scratch disk that can read and write at these speeds can really help to speed up a project’s workflow, especially with 4K footage. This reviewer, for example, will be utilizing this SSD as their Photoshop drive where he constantly edits multi-gigabyte image files. Some users have even reported that having this SSD with such high speeds and low latency compared to their SATA 6Gb/s SSDs that stuttering during map and texture loading has been eliminated when gaming. Taking into consideration how large games are getting these days we don’t doubt it. GTA V requires 65GB alone and with more 4K support being released many others can take advantage of these ultra-fast speeds for best performance.

One of the main issues with buying one of these SSDs is concern with using it as a boot drive in your system. While most Z97 and X99 systems can boot off this SSD, older systems, except for some Z87 motherboards will most likely not boot off of it. We even had to update our test bench’s UEFI in order to do so. This, however, begs the question, “if you want to spend the money for one of the fastest SSDs out, shouldn’t you have a fast modern system to put it in by now as well?” Also, if you are betting on using this in your motherboard’s M.2 slot, in order to attain similar speeds that you have seen here, you need to make sure the M.2 slot is PCIe 3.0 x4 capable, otherwise you will be a bit disappointed. Luckily there are M.2 to PCIe adapters that be purchased at a low cost for those who need them.

Samsung SM951 AHCI M.2 PCIe 512GB Main

While this is not a retail product, it is a very competitive SSD when look at price to performance and it is now readily available. For this we awarding it our editor’s choice award. The Samsung SM951 is one of the fastest SSDs out. If you are looking for a fast M.2 SSD and have a compatible system, this one will not disappoint.

All that is left for us to do now is wait for an NVMe variant to come into our hands so we can see how that affects performance!

TSSDR Editors Choice Opt

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Review Overview

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One Fast Gum Stick!

The SM951 is Samsung's second generation M.2 PCIe SSD. It utilizes their UBX controller and 16nm Toggle MLC NAND. This time around the SM951 supports the PCIe 3.0 bus and delivers insane read and write speeds reaching over 2.2GB/s and 1.6GB/s respectively. The only issue around this SSD is compatibility, but if your system is compatible with it, this high-speed M.2 SSD will give you some of the best performance you can attain.

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