Samsung 850 EVO 500GB review

3D stacked memory comes to the mainstream

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Our Verdict

The fastest mainstream SSD around, just not necessarily one to shake the solid state world.


  • Speedy performance
  • Good-value
  • Five-year warranty


  • Not a huge generational leap
  • Definitely consumer-class SSD

The Samsung 850 EVO is the latest in its affordable line of performance SSDs and shows Samsung's desire to push the solid state game along, even at the lower end of the price/performance stack.

When it comes to solid state drives Samsung has really nailed its colours to the mast; it's going to be first to market with new technologies, it's going to aggressively drive pricing down and it's going to do it all alone.

To that end, the Samsung 850 Pro was the first consumer SSD to arrive on the scene with 3D stacked memory making up its various capacities. The Samsung 850 EVO follows this trend, using another spin of the V-NAND technology for it's more price-conscious range of SSDs. And, as is its wont, Samsung is purely using its own technology - its own memory and controllers - for its drives.

The new 3D V-NAND - Samsung is calling it vertical NAND - is designed to offer a path up to higher capacity SSDs in the coming years.

The literal idea of stacked memory is to pile NAND chips on top of each other, with through-silicon vias (TSV) providing connections down directly through the stack. This helps boost the bandwidth, as the connections are physically closer, but also means higher capacity drives can be made without relying on the ever-shrinking of NAND modules which make up our SSDs.

Samsung's second-gen 3D V-NAND is made up of a full 32 layers stacked atop each other in each module. Those modules have a total density of 86Gbit.


Now, that's not the highest density NAND you'll find in today's drives - both Crucial and Intel are throwing out drives with 128Gbit density NAND in them and have partnered up to create their own 256Gbit 3D NAND for 2015 - but the difference is Samsung is only using 40nm silicon to get there.

Because of the celebrated shrinking of production processes in all spheres of computing - from processors to memory to graphics chips - it might at first seem like this is a backwards step.

We have, after all, become used to using 19nm NAND in our SSDs, even going as low as 16nm, so using a production process that's more than twice as large would surely undo all the performance and efficiency boosts we picked up along the way down.

But because of 3D V-NAND's ability to hit these high densities with such chunky lithography, combined with the bandwidth boosts of the TSVs inside the stacked modules, the larger dies don't have any impact on relative performance.

The efficiency gains from previous production shrinks are also largely offset by the power reductions in the switch from 2D to 3D NAND.

Samsung estimates a 30% reduction in operational power with the Samsung 850 EVO compared with the older Samsung 840 EVO.

Hardy NAND

The 40nm process comes into its own though when we start talking about endurance.

The biggest benefit is the fact the larger production processes are more reliable and longer-lived than their smaller descendants. When you're making the switch, as Samsung is, from the 2-bit multi-layer cell (MLC) design of its higher-end 850 Pro to the less-robust 3-bit MLC, any endurance boost is welcome.

Traditionally 3-bit MLC doesn't last so long as the 2-bit kind, which is why you'll see the Samsung 850 Pro rocking a full ten-year warranty.

With the 40nm 3-bit MLC of the Samsung 850 EVO it does have a shorter five-year warranty, but that's still a good deal longer than the rest of the affordable SSD world with their three-year hedged bets.