SAMSUNG 850 PRO 1TB
£365 inc VAT • samsung.com/uk
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
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.