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WD Black SN850X SSD Review: Back in Black

The WD Black SN850X is one of the fastest drives around for gaming.

WD Black SN850X
Editor's Choice
(Image: © Tom's Hardware)

Tom's Hardware Verdict

The WD Black SN850X is a powerful, high-end PCIe 4.0 SSD that's near the top of the heap in almost every category. The SN850X is available in high capacities and has an optional RGB-laden heatsink for most models, but pricing and the questionable Game Mode 2.0 keep it from being the very best.


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    Excellent performance

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    Optional heatsink/RGB and a good range of capacities

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    Software support with sufficient warranty


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    Game Mode 2.0 is a bit gimmicky

Western Digital touts the WD Black SN850X as a high-end PCIe 4.0 SSD for gaming that has options for RGB lighting and a heatsink, making it ready for the PlayStation 5 (PS5) or your PC. The 4TB model is especially enticing as many drives, like the SK hynix Platinum P41, are still limited to a peak of 2TB. The SN850X also has faster sequential performance and IOPS than its predecessor, the popular WD SN850, and a new Game Mode 2.0 to improve your gaming experience.

It does feel like the SN850X is a bit tardy, as it’s been eighteen months since WD launched the SN850. Since then, the high-end SSD game has evolved rapidly to include an array of serious contenders. Luckily, the SN850X can compete with any of them, although the launch pricing might be a bit too lofty given recent pricing trends.

We also need to test to see if WD's new Game Mode is just a gimmick. We took a deep-dive look at Microsoft's DirectStorage feature in our recent Phison I/O+ firmware preview. This new Microsoft feature will drastically reduce game loading times, and the previous-gen SN850 performed fairly well in our tests, all things considered, setting a high bar for its predecessor.

WD's NAND technology still lags behind its competitors, with its 112-Layer BiCS5 flash competing against 176-Layer flash from Micron and SK hynix. However, this has advantages, as WD's mature flash can be carefully and reliably binned. BiCS5 also has 1Tb dies available for higher-capacity SSDs.

The previous-gen SN850 didn't set any performance records, but we can also see improvements to the SN850X's SSD controller across the performance spectrum. It’d still be a hard sell for this to beat the SK hynix Platinum P41 that leads our list of Best SSDs, but WD has surprised us before. Here's how the WD Black SN850X stacks up.  


Pricing | w/HS $159.99 / $179.99 $289.99 / $309.99 $699.99
Capacity (User / Raw)1000GB / 1024GB2000GB / 2048GB4000GB / 4096GB
Form FactorM.2 2280M.2 2280M.2 2280
Interface / ProtocolPCIe 4.0 x4PCIe 4.0 x4PCIe 4.0 x4
ControllerWD ProprietaryWD ProprietaryWD Proprietary
Flash Memory112-Layer BiCS5 TLC112-Layer BiCS5 TLC112-Layer BiCS5 TLC
Sequential Read7,300 MBps7,300 MBps7,300 MBps
Sequential Write6,300 MBps6,600 MBps6,600 MBps
Random Read800K1,200K1,200K
Random Write1,100K1,100K1,100K
Endurance (TBW)600TB1200TB2400TB
Part Number | w/HSWDS100T2X0E / WDS100T2XHEWDS200T2X0E / WDS200T2XHEWDS400T2X0E
Height | w/HS2.38mm / 8.80±0.22mm2.38mm / 8.80±0.22mm2.38mm / 8.80±0.22mm

The Western Digital Black SN850X is available in 1TB, 2TB, and 4TB capacities. This is a departure from the earlier SN850, which had no 4TB model but did have a 500GB variant. In addition, the SN850X has options for a heatsink with RGB for the 1TB and 2TB models, but not for the 4TB drive. In contrast, the SN850 had a non-RGB heatsink option for every capacity. 

WD touts the 1TB and 2TB capacities as the best for the PS5; the RGB and heatsink only add $20 to the price tag. The SN850X's rated endurance remains the same at 600TB of writes-per-TB of capacity over five years — this is pretty typical, and more than enough for normal use.

WD improved performance in sequential read workloads, with a maximum of 7.3GBps from 7.0GBps, and sequential writes improved from up to 5.3GBps to 6.6GBps. Performance in random workloads has also improved significantly, up from a maximum of 1M / 720,000 read and write, respectively, to 1.2M / 1.1M. 

The SN850X is competitive with other high-end PCIe 4.0 drives in sequential workloads, but it can’t quite match the SK hynix Platinum P41 in random IOPS. Pricing is a bit stiff, particularly at 4TB. The SN850X will have to impress to justify its MSRP.

Game Mode 2.0, Software and Accessories

The Black SN850X works with WD's Dashboard management software that the company includes with its SSDs. This application can quickly display information about the drive, including health status, while also providing tools and settings.

Of particular note is the Game Mode 2.0 feature that's new with the SN850X. The original Gaming Mode could be turned on or off within the Dashboard, but Game Mode 2.0 has an additional Auto setting to detect game launches. You can also manually enter game folder locations so the software knows where to watch.

The SN850's Gaming Mode worked by disabling lower power states, ensuring the drive would be more responsive. Game Mode 2.0 works differently with a three-pronged approach: predictive loading, adaptive thermal management, and overhead balancing. Predictive loading is an algorithm designed to detect upcoming low queue depth, sequential workloads - particularly the read workloads prevalent in many games. Adaptive thermal management works to improve average and sustained throughput via smoother throttling. Finally, overhead balancing seeks to improve read latency while gaming through I/O prioritization.

These changes are all geared towards gaming and reflect some of the elements we saw with Phison's I/O+ firmware. Consistent, sustained reads are a hallmark of optimal DirectStorage performance. You want to avoid peaks and troughs, which can introduce jitter. Smoothing out the response through throttle avoidance helps here, particularly on hotter-running PCIe 4.0 drives. We also saw Phison prioritize host I/O via scheduled background management, which WD mirrors with overhead balancing. Current games are more likely to benefit only in load times with low queue depth reads, so WD is covering all of its bases with predictive loading.

A Closer Look

We're reviewing the base or bare version of the SN850X, so our drive has only an informative label on the front. Like previous WD models, this drive is single-sided, which can be advantageous for compatibility and cooling. The drive's controller is close to the M.2 interface, a package of DRAM, and two packages of flash.

The controller appears to be an updated version of the one found on the SN850. It’s still eight-channel but is paired with faster flash and improved firmware. WD tends to have excellent firmware, perhaps best exemplified in the SN770. The SN850 also did relatively well in our Phison I/O+ firmware preview, performing quite consistently. The Game Mode 2.0 optimizations should make the SN850X even better there, although it’s still too early to make judgments on game applicability.

The DRAM module is labeled D9XPG, a 16Gb DDR4 module from Micron with 16-bit width. This is 2GB of memory and meets the ideal ratio of DRAM to NAND for the 2TB test sample.

(Image credit: Tom's Hardware)

WD has updated the BiCS4 found on the SN850 to BiCS5 on this drive. BiCS5 is also on the SN770 and some odd drives like Sabrent’s 8TB Rocket 4 Plus. Each flash package is 1TB in capacity, with what we expect is sixteen dies per package. WD can use 512Gb dies for lower capacities, but 1Tb dies are necessary to keep the drive single-sided at 4TB. This indicates that both the 2TB and 4TB SKUs have the ideal amount of total dies, that is thirty-two (four per channel), for peak performance.

BiCS5 didn’t quite pan out the way WD and Kioxia had originally planned. However, BiCS6 and BiCS+ still appear on target with important changes to the flash’s architecture. BiCS5 is ostensibly behind the competition, particularly the 176-layer flash from SK hynix and Micron. However, WD has made the most of its flash and can manage trade-offs by using a mature architecture.


MORE: How We Test HDDs And SSDs

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Shane Downing
Freelance Reviewer

Shane Downing is a Freelance Reviewer for Tom’s Hardware US, covering consumer storage hardware.

  • tommo1982
    The Black series is a bit too expensive for me. I find the Blue one good value for the money, though. The NVMe version has reasonable price tag and performance and would be me first choice. I like WD's own controlers. It adds some flavour to the market.
    I generally prefer WD since the HDD time, so I might be somewhat biased 😊
  • elforeign
    The pricing is off for this product. You can regularly find the SK Hynix Platinum 1 and 2tb for below MSRP. The 2TB will go for $207 and is a better product overall. I don't see the point for WD to price this at this level. I wouldn't even consider this drive.
  • -Fran-
    Crucial P5P and Samsung 980 Pro (after the discounts) are great value drives. That is what I can conclude from this.

    This WD drive is too expensive for what it offers. Maybe when it drops to a similar price range of the P5P and 980Pro, it'll be a good buy. Not before. Well, for "value" seekers. Performance seekers are better off waiting for PCIe5 drives anyway.

  • kiniku
    When DirectStorage gets off the ground even the slower NVMe SSD's will be unshackled by Windows and be screamers in gaming. So as the writer noted, this is kind of an apple and oranges performance comparison today, at least for gamers.
  • listless
    I just bought an SN850X 1TB for $130 USD. Not a bad price, AFAIC. No issues. The WD Dashboard software made updating the firmware super easy, as opposed to the hour+ of struggle I suffered through trying to get the firmware on my Seagate FireCuda 520 updated with a mega-finicky command line utility and confusing documentation (oh -- and the firmware function in the SeaTools SSD GUI utility simply doesn't work at all).