Internals, Testing Methodology and System Setup


Cracking these open, I expected to see some sort of PCB changes as comapred to the 1TB and lower models of the 850 EVO and Pro. Let's see what has changed:

There have been some changes, but they are more minor than expected. The PCB is the same physical size as compared to prior high capacity models (more on that further down the page), however the layout has changed slightly. On the surface it looks like a simple revision to the PCB that was carried across both lines.

With the PCB's out, lets take a closer look at things here:

850 EVO 2TB:

Front and center we find Samsung's new MHX controller. This is a beefier version of the MEX (1TB) and MGX (120/250/500GB) controllers used in the smaller versions of the 850 EVO. As you can see, Samsung has had to step this controller up in two speed/capability grades as supported capacities have gotten larger.

Further around the controller we see necessary DRAM for the controller's use as well as four flash packages. With some decryption of the part numbers and math, these are 3-bit MLC (TLC) 16-die stacks.

At the rear we find four more pacakges of identical nomenclature, bringing the total count of TLC VNAND dies to 128 – a neat doubling of the 1TB model.

850 Pro 2TB:

On the 850 Pro we see the same layout as well as the same MHX controller (all smaller capacities of the Pro employ the MEX controller). We also see four flash packages with part numbers previously unseen. More on that after this pic of the rear:

An interesting note on the flash memory configurations of both the EVO and Pro is that previous models employed asymetric staggering of flash die counts per package within each series. The 840 EVO had staggered flash package capacities while the 840 Pro was symetrical. The (1TB and below) 850 Pro models had staggered capacities while the 850 EVO was symetrical. This flip was due to Samsung's VNAND die capacity being 50% away from an even power of two in MLC form (86 Gbit), while their older planar NAND used in the 840 series was 50% away from an even power of two in TLC mode.

If the above paragraph was confusing, it should be, and staggering die capacities to a connected SSD controller makes performance tuning potentially more complex.

  • Possibility #1: With a total of 192 (!) VNAND dies in the 2TB 850 Pro, Samsung opted to spin a custom package type containing 24 86 Gbit dies. This way the die count per package falls between a power of two multiple, and the MGX controller can neatly address each package full of VNAND in an identical fashion.
  • Possibility #2a: Going strictly off of the 'D' in the part numbers, which suggests the 2TB 850 Pro is still using 16 die stacks, that would suggest that Samsung has silently launched 128 Gbit capacity 32-layer VNAND dies.
  • Possibility #2b: Still 16 die stacks, but Samsung might have increased capacity by instead moving to the same die footprint but a 48-layer VNAND stack.

As a bonus, partially because I got a bit too overzealous with the iFixit toolkit, here's the full capacity series of the 850 Pro:

The 850 EVO series is a bit different, mainly in the form of even smaller PCBs in the low capacity models, as only a single flash package of TLC VNAND is sufficient for the 120GB model.

Testing Methodology

Our tests are a mix of synthetic and real-world benchmarks. IOMeter, HDTach, HDTune, Yapt and our custom File Copy test round out the selection to cover just about all bases. If you have any questions about our tests just drop into the Storage Forum and we'll help you out!

Test System Setup

We have several storage testbeds. A newer ASUS P8Z77-V Pro/Thunderbolt and an ASUS Z87-PRO. Variance between both boards has been deemed negligible when testing SATA devices. Future PCIe and SATA device testing, including this review, take place on a new ASUS Sabertooth X99, which comes equipped with USB 3.1, M.2, and can also handle SFF-8639 devices with the proper adapter.

PC Perspective would like to thank Intel, ASUS, Corsair, Kingston, and EVGA for supplying some of the components of our test rigs. 

Hard Drive Test System Setup
CPU Intel Core i7 5820K @ 4.125 GHz
Motherboard ASUS Sabertooth X99
Memory 16GB Micron DDR4 @ 3333
Hard Drive G.Skill 32GB SLC SSD
Sound Card N/A
Video Card EVGA GeForce GTX 750
Video Drivers GeForce Game Ready Driver 347.88
Power Supply Corsair CMPSU-650TX
DirectX Version N/A
Operating System Windows 8.1 Pro X64 (update)
  • PCPer File Copy Test
  • HDTach
  • HDTune
  • IOMeter
  • YAPT
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