Samsung 850 Evo M.2 review: good things come in small packages

Reviews, Storage

Samsung 850 Evo M.2

Today we’re looking at the M.2 version of Samsung’s popular 850 Evo SSD. We’ve already benchmarked the 2.5-inch 840 Evo and 850 Evo, so we’re curious to see how this smaller form factor shapes up. Thanks to Samsung, we’ve got our hands on a unit to serve in our XSR test rig, so let’s take a look!


  • Pretty fast
  • Super tiny

  • Not the fastest
  • Limited to SATA speeds

Summary and Score

score8-gif-200Based on our tests, the 850 Evo M.2 is a strong performer and a good choice for a small form factor PC or laptop where saving space is a large concern. Otherwise, we’d recommend sticking with the 2.5-inch version, which is currently £10 cheaper.


  • Interface: M.2 / SATA 6GB/s
  • Sequential Read Speed: up to 540MB/s
  • Sequential Write Speed: up to 500MB/s
  • Capacity: 120 GB
  • Memory Speed:
    • Samsung 32-layer 3D V-NAND
    • Samsung 512MB Low Power DDR3 SDRAM



The nice thing about M.2 SSDs is that you can really take a look at them; there’s no case to get in the way. Of course, then you’re going to put it on a motherboard and never see it again until you upgrade, but it’s still nice to look at. We’ve already seen the front, so here’s the (more exciting) back of the drive.


Samsung have also prepared a nice box. n.b. these images are from the 500GB version; we’re looking at the 128GB version.3

The five year warranty is a nice touch, and a fairly safe bet for Samsung given the sturdiness of solid state drives. Not having any moving parts is a pretty good way to avoid mechanical failures.2


As there’s little real-world analysis to be done, we’ll be strictly in benchmark land for the majority of this article. We’ll be testing the M.2 Samsung drive against three 2.5-inch SSDs — the Samsung 850 Evo, 840 Evo and Corsair Neutron GTX — in a battery of tests to see which is the fastest.

It’s worth noting that our other test subjects are 250GB, 1TB and 240GB, respectively, so there will be some variations, particularly in write speed. 

The test rig has a Core i6 6600K processor, 16GB of DDR4 RAM and the OS is Windows 10. 

Thanks to NZXT for providing the Manta case and Kraken X61 liquid cooler. Thanks to Samsung for providing the Evo 850 M.2 boot drive. Thanks to Zoostorm and Crucial for providing the DDR4 RAM.


CrystalDiskMark has been one of my favourite benchmarks for evaluating storage speeds for a while now, thanks to its varied incompressible workload and extremely readable results. Here’s the 3.0.3 x64 version of the benchmark; all results are in MB/s.

CDM 3 Read Seq 512K 4K 4K QD32
Samsung 850 Evo M.2 502 447 45 368
Samsung 850 Evo 513 472 38 408
Samsung 840 Evo 515 473 35 397
Corsair Neutron GTX 450 376 27 328
CDM 3 Write Seq 512K 4K 4K QD32
Samsung 850 Evo M.2 474 394 113 316
Samsung 850 Evo 504 479 68 352
Samsung 840 Evo 500 390 86 313
Corsair Neutron GTX 480 468 69 158

In our first test, we see that the M.2 SSD is lagging behind its 2.5-inch counterparts. We’re expecting a small decrease in performance due to the smaller capacity of our test drive — 128GB versus 250GB — and that’s reflected in the results. Still, the M.2 drive keeps pace with the 840 and 850 in most of the tests, and beats the Neutron GTX comprehensively in our read tests. The drive does record our highest-ever score in the 4K section of the test, beating out even the 1TB 850 Evo.

AS SSD Benchmark

AS SSD is another benchmarking tool quite similar to CrystalDiskMark, which uses predominantly incompressible data across a range of workloads including sequential tests, random performance and access times. First three numbers are MB/s and access time is in ms.

AS SSD Read Seq 4K 4K QD64 Acc. Time Score
Samsung 850 Evo M.2 493 40 328 0.093 417
Samsung 850 Evo 516 34 382 0.059 467
Samsung 840 Evo 513 32 330 0.059 413
Corsair Neutron GTX 507 25 334 0.068 N/A
AS SSD Write Seq 4K 4K QD64 Acc. Time Score
Samsung 850 Evo M.2 475 95 251 0.075 393
Samsung 850 Evo 497 66 299 0.051 415
Samsung 840 Evo 497 69 207 0.054 326
Corsair Neutron GTX 473 62 295 0.062 N/A

As queue depth increases, the 850’s strengths (on both M.2 and 2.5-inch form factors) become more apparent. Otherwise, the M.2 interface and smaller capacity lead to a slight performance regression, with almost doubly-slower access times (albeit still under 0.1ms) and slower sequential results than either Samsung 2.5-inch drive.

However, the M.2 card does display faster speeds than its competitors when reading or writing small 4K blocks, a task that commonly occurs on booting a system and in some games (depending on how they’re designed).

ATTO Disk Benchmark

ATTO produces rather less comprehensible results than CrystalDiskMark, but still provides a good test of compressible data transfer. It also provides a lot of data points; I’ve selected six from across the range. Settings were the default: 256MB total length and queue depth of 4, testing from 1KB to 8MB. All results are in MB/s.

Atto Read 1KB 4KB 64KB 256KB 1MB 8MB
Samsung 850 Evo M.2 83 286 537 553 552 553
Samsung 850 Evo 80 269 538 551 558 558
Samsung 840 Evo 94 280 535 551 555 555
Corsair Neutron GTX 15 61 336 452 530 540
Atto Write 1KB 4KB 64KB 256KB 1MB 8MB
Samsung 850 Evo M.2 79 251 510 526 525 525
Samsung 850 Evo 83 255 519 529 534 534
Samsung 840 Evo 81 260 515 527 533 534
Corsair Neutron GTX 15 142 474 470 493 498

Once again the M.2 edition of the 850 Evo remains largely on track with its 840 and 850 counterparts, remaining within 1% of the drives at the highest block size when reading, and not much lower elsewhere in the read tests. During writing, the speeds are around 2% of the 850 and 840’s speeds during the largest 8MB block test, and again fairly similar throughout. This is a promising sign, given the smaller capacity of the drive, which normally translates into slightly slower write speeds.

HD Tune Pro

We conclude with HD Tune Pro, a benchmark which produces three scores for average read speed, read access time, and burst read rate.

HD Tune Pro 5.50 Read Average Access Time Burst Rate
Samsung 850 Evo M.2 321 MB/s 0.087 ms 221 MB/s
Samsung 850 Evo 370 MB/s 0.044 ms 250 MB/s
Samsung 840 Evo 358 MB/s 0.041 ms 231 MB/s
Corsair Neutron GTX 340 MB/s 0.059 ms 231 MB/s

The M.2 drive shows slightly worse results across the board, with a read speed average that’s even worse than the Corsair Neutron GTX. The access time is also poor, as we’ve seen in earlier tests. Still, it’s once again within that 0.1ms benchmark, so it’s not a massive deal.

Comparison: Samsung 950 Pro vs 850 Evo


The most recent Samsung M.2 drive is the 950 Pro, which is also available in the same M.2 form factor as the 850 Evo we’re looking at today. This drive is twice as expensive, but it uses the faster NVMe interface to allow for higher speeds — around 2500MB/s reading and 1500MB/s writing. That’s about 5x faster reading and 3x faster writing compared to the 850 Evo M.2. Check it out on Amazon via the link below!


The Samsung M.2 850 Evo is a strong performer that makes sense for laptops and mini-ITX PCs. While the 2.5-inch model provides a bit better performance and is available for a lower price, if you need an M.2 drive then you needn’t worry about performance.


Thanks to Samsung for providing the 850 Evo M.2 sample, and for allowing us to hang onto it for our future reviews! You’ll be seeing this drive again in our NZXT Manta review (coming soon), and hopefully for many more in the future.

Last modified: August 20, 2016

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