Samsung 850 EVO 500GB review

3D stacked memory comes to the mainstream

Samsung 850 EVO 500GB
The new price/performance SSD king?

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But what of performance? Sadly this is where we're in a bit of a holding pattern with solid state drives at the moment. Because of the performance limitations of the SATA 6Gbps interface there's a hard 600MB/s speed limit in place on connected drives.

The solution to this has been the introduction of the M.2 PCIe-based interface, which doesn't have such tight restrictions. Unfortunately they're still limited by the spinning platter HDD legacy of the traditional AHCI protocols which dictate how the interface operates.

This will change once the first non-volatile memory express (NVMe) drives are introduced, combining the PCIe interface with a new standard, designed from the ground up for the NAND memory used in SSDs.

For now though Samsung's consumer drives are all about the ol' SATA 6Gbps interface and so performance really hasn't changed a huge amount from the previous generation of EVO drives.

That is though all relative to the performance hikes we've been spoiled with in the early days of the SSD market.

Spoiled rotten

The Samsung 850 EVO is definitely quicker than the older Samsung 840 EVO, but not by the sort of performance metrics that are going to have you rushing out to upgrade.

The biggest change has been in the write performance of the new Samsung 850 EVO. In sequential terms you're looking at some 20% quicker than the Samsung 840 EVO and a full 30% quicker for the 4k random writes.

The 4k numbers represent the tiny, itty-bitty reads and writes that an operating system will be carrying out on a regular basis as you use your PC. As such they're a good indication of how responsive your PC will be running from that drive.

Samsung 850 EVO open

Those are decent improvements and mean that in the real-world we saw our 30GB Steam folder transfer test resolve twenty-two seconds quicker than the Samsung 840 EVO.

These are the results for the 500GB version of the Samsung 850 EVO, but the introduction of a new Samsung controller - the MGX - for the capacities of 500GB and below has been primarily tuned to provide consistent performance across the range.

That means the performance of the cheaper 250GB version is almost identical.

Still perfectly formed

In fact, the slight difference between the synthetic numbers of the 250GB and 500GB drives could arguably be put down to standard variances in testing.

The real-world scores though are a little slower for the smaller drive. Our zip compression and folder transfer tests show the 500GB drive comfortably ahead.

That might well be down to the TurboWrite tech Samsung uses to speed up its 3-bit MLC drives.

TurboWrite apportions some of the drive's capacity to be used as a form of pseudo single level cell (SLC) NAND. SLC is quicker than the 3-bit MLC used throughout the rest of the drive and acts almost like a speedier form of cache.

There are different amounts of NAND given over to emulating SLC for each capacity of drive; if it follows the Samsung 840 EVO range the 250GB will effectively utilise 3GB of SLC and the 500GB doubles that to 6GB.

If an operation doesn't use the full extent of the pseudo-SLC, and is given time to idle and flush the cache in between tasks, the drive will run at full speed. If it exceeds that limit, such as in our real-world tests, then the drive will revert to a slower 3-bit MLC speed.

This would explain the difference in real-world performance between the different capacity drives, despite their comparable synthetic benchmarks. Our zip test uses a 5GB game folder and the 30GB transfer is a packed Steam installation folder.


Sequential read performance
AS SSD - MB/s: higher is better
Samsung 850 EVO 500GB - 494
Samsung 840 EVO 500GB - 496
Crucial MX100 512GB - 499
SanDisk Extreme Pro 512GB - 506
Samsung 850 Pro 512GB - 528

Sequential write performance
AS SSD - MB/s: higher is better
Samsung 850 EVO 500GB - 485
Samsung 840 EVO 500GB - 409
Crucial MX100 512GB - 474
SanDisk Extreme Pro 512GB - 474
Samsung 850 Pro 512GB - 502

4k random read performance
AS SSD - MB/s: higher is better
Samsung 850 EVO 500GB - 36
Samsung 840 EVO 500GB - 26
Crucial MX100 512GB - 24
SanDisk Extreme Pro 512GB - 30
Samsung 850 Pro 512GB - 37

4k random write performance
AS SSD - MB/s: higher is better
Samsung 850 EVO 500GB - 108
Samsung 840 EVO 500GB - 82
Crucial MX100 512GB - 106
SanDisk Extreme Pro 512GB - 103
Samsung 850 Pro 512GB - 107

Real-world performance
30GB Folder copy - Time in seconds: quicker is better
Samsung 850 EVO 500GB - 208
Samsung 840 EVO 500GB - 230
Crucial MX100 512GB - 191
SanDisk Extreme Pro 512GB - 191
Samsung 850 Pro 512GB - 191