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Sam­sung has two se­ries of SSDs avail­able for com­puter up­graders, both des­ig­nated 850 and then di­vided into 850 PRO and 850 EVO ranges. As may be ev­i­dent from the nam­ing scheme, the for­mer PRO mod­els are de­signed for high­est per­for­mance, while the EVO range trades a lit­tle speed and en­durance for a lower en­try price.

What both have in com­mon is the core sil­i­con ar­chi­tec­ture that is now based on 3D NAND, or V-NAND, where the V is for ver­ti­cal. This is the ap­pli­ca­tion of three-di­men­sional in­te­grated cir­cuit con­struc­tion tech­niques, which just like hu­man cities over­come the prob­lem of over-crowd­ing by build­ing not side­ways, but up­wards.

Us­ing 3D lithog­ra­phy, flash cells are built layer by layer on top of each other, 32 lay­ers high here, giv­ing a higher den­sity of stor­age that means that even for the 1TB sam­ple we tested, for ex­am­ple, the PCB in­side only takes up two-thirds of the large 2.5in SATA case.

As with the 840 Se­ries, the dif­fer­ence be­tween PRO and EVO mod­els is the type of flash cell em­ployed; the 850 PRO uses more re­silient multi-layer cell (MLC, and in par­tic­u­lar the two-bit ver­sion) while the 850 EVO takes the latest three-layer cell (TLC), which al­lows more stor­age per square cen­time­tre of sil­i­con wafer, but loses out in long-term longevity and is slower to write to.

The 850 PRO is a great ex­am­ple of how Sam­sung can build an en­tire SSD with parts it makes it­self to its own spec­i­fi­ca­tion. So we have a Sam­sung-made MGX Con­troller chip based on a three­core ARM pro­ces­sor, 1GB of Sam­sung low-power DDR2 RAM and, of course, the NAND flash piled up to in Sam­sung’s new semi­con­duc­tor process, still unique in flash mem­ory.

The process size has ac­tu­ally gone up, from the 19- or 20nm com­mon to other brands, up to 40nm, po­ten­tially con­fer­ring greater longevity while de­liv­er­ing bet­ter speed. This has inspired Sam­sung

Sup­port Per­for­mance



to of­fer one of the long­est guar­an­tees avail­able, 10 years, match­ing the of­fer first made by SanDisk with its Ex­treme PRO SSD.

Sam­sung has also been work­ing on the power ef­fi­ciency is­sue, and with the help of a spe­cial sleep state that can be used by some lap­tops, pub­lishes a low­est-in-class power con­sump­tion fig­ure of just 2mW when in this DEVSLP mode.


The 850 PRO strolled through our read/write tests, reach­ing 564MB/s for reads and 534MB/s writes in the ATTO bench­mark test. Com­par­ing the Crys­talDiskMark re­sults for stan­dard ran­dom and com­press­ible ze­roes, we see the same level of per­for­mance at around 510MB/s sequential read­ing and 480MB/s writ­ing.

The 4kB sin­gle-thread ran­dom IO tests place the Sam­sung ahead in the 4kB ran­dom-read list with 36MB/s, while the 89MB/s write speed is im­pres­sive, a trend that con­tin­ued when the SSD was stretched when field­ing the high queue-depth test – the 403MB/s ran­dom reads and 366MB/s ran­dom writes makes the 850 PRO the top of the IOPS with 103,200 read IOPS and 93,700 write IOPS.

When run­ning the com­pa­ra­ble test from AS SSD it re­mained in the over-achiev­ers class with 96,800 read IOPS and 81,400 write IOPS. The AS SSD bench­mark awarded the Sam­sung 850 PRO an over­all nom­i­nal score of 1145 points, the best over­all re­sult in this group. VER­DICT: The 850 PRO ar­rived just too late for last year’s round-up of SSDs, but even a year later it still has lit­tle se­ri­ous com­pe­ti­tion. It may be left for dust by more mod­ern PCIe drives like Sam­sung’s own XP941, but if you have a SATA-based PC and want to fit it with the best stor­age, take the clos­est look at the 850 PRO.

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