Western Digital touts the WD Black SN850X as a high-end PCIe 4.0 SSD for gaming, with RGB lighting and heatsink options, and PlayStation 5 (PS5) or PC ready. The 4TB model is particularly attractive as many drives such as the SK hynix Platinum P41 are still limited to 2TB peak. The SN850X also features faster sequential performance and IOPS than its predecessor, the popular WD SN850, and a new Game Mode 2.0 that enhances the gaming experience.
It’s been 18 months since WD launched the SN850, so the SN850X feels a bit behind the times. Since then, the high-end SSD game has evolved rapidly to include a series of serious competitors. Luckily, the SN850X can compete with any of them, but given recent pricing trends, it might be priced a little too high at launch.
We also need to test whether WD’s new game mode is just a gimmick. A recent Phison I/O+ firmware preview took a closer look at Microsoft’s DirectStorage feature. This new feature from Microsoft resulted in significantly faster loading times for games, and the previous-gen SN850 performed pretty well in our tests, all things considered, setting a high bar for the previous generation.
WD’s NAND technology still lags behind its competitors, with its 112-layer BiCS5 flash competing against Micron and SK hynix’s 176-layer flash. However, this has its advantages as it allows you to carefully and reliably bin WD’s mature flash. BiCS5 also has a 1Tb die that can be used for high capacity SSDs.
While the previous generation SN850 didn’t set performance records, we also see improvements in the SN850X’s SSD controller across the performance spectrum. It’s still going to be hard for this to beat the SK hynix Platinum P41, which leads the list of best SSDs, but WD has surprised us before: Here’s the WD Black SN850X pairing.
specification
| product | 1TB | 2TB | 4TB |
|---|---|---|---|
| Price | With HS | $159.99 / $179.99 | $289.99 / $309.99 | $699.99 |
| Capacity (User / Raw) | 1000GB/1024GB | 2000GB/2048GB | 4000GB/4096GB |
| form factor | M.2 2280 | M.2 2280 | M.2 2280 |
| interface/protocol | PCIe 4.0 x 4 | PCIe 4.0 x 4 | PCIe 4.0 x 4 |
| controller | WD exclusive | WD exclusive | WD exclusive |
| DRAM | DDR4 | DDR4 | DDR4 |
| flash memory | 112-layer BiCS5 TLC | 112-layer BiCS5 TLC | 112-layer BiCS5 TLC |
| Sequential read | 7,300MBps | 7,300MBps | 7,300MBps |
| Sequential write | 6,300MBps | 6,600MBps | 6,600MBps |
| random read | 800K | 1,200K | 1,200K |
| random write | 1,100K | 1,100K | 1,100K |
| safety | none | none | none |
| Endurance (TBW) | 600TB | 1200TB | 2400TB |
| Part number | With HS | WDS100T2X0E / WDS100T2XHE | WDS200T2X0E / WDS200T2XHE | WDS400T2X0E |
| Height | With HS | 2.38mm/8.80±0.22mm | 2.38mm/8.80±0.22mm | 2.38mm/8.80±0.22mm |
| guarantee | 5 years | 5 years | 5 years |
The Western Digital Black SN850X is available in 1 TB, 2 TB, and 4 TB capacities. This sets it apart from the previous SN850, which didn’t have a 4TB model and had a 500GB variant. Additionally, the SN850X has options for heatsinks with RGB for the 1TB and 2TB models, but not for the 4TB drives. In contrast, the SN850 had a non-RGB heatsink option on all capacities.
WD touts 1TB and 2TB capacities as optimal for the PS5. The RGB and heatsink only add $20 to the price tag. The SN850X endurance rating remains the same at 600 TB writes per 1 TB of capacity over five years. This is a fairly typical value and more than sufficient for normal use.
WD boosts performance for sequential read workloads, up from 7.0GBps to 7.3GBps, and sequential writes from up to 5.3GBps to 6.6GBps. Performance on random workloads has also improved significantly, increasing from up to 1M / 720,000 reads and writes to 1.2M / 1.1M respectively.
The SN850X competes with other high-end PCIe 4.0 drives in sequential workloads, but can’t match the SK hynix Platinum P41 in random IOPS. The price is a bit stiff, especially for 4 TB. The SN850X has to impress to justify its MSRP.
Game Mode 2.0, software and accessories
The black SN850X works with WD’s dashboard management software, which the company ships with the SSD. The application can quickly display information about the drive, such as health status, while providing tools and settings.
Of particular note is the newly added Game Mode 2.0 feature on the SN850X. While the original Game Mode could be turned on or off within the Dashboard, Game Mode 2.0 has an additional automatic setting that detects game launch. You can also manually enter the game folder location so the software knows where to watch.
Game Mode on the SN850 worked by disabling low power states, making the drive more responsive. Game Mode 2.0 works differently with three approaches: predictive loading, adaptive thermal management, and overhead balancing. Predictive loading is an algorithm designed to detect upcoming low queue depth sequential workloads, especially read workloads common in many games. Adaptive thermal management improves average and sustained throughput with smoother throttling. Finally, overhead balancing attempts to improve in-game read latency through I/O prioritization.
These changes are all for gaming and reflect some of the elements seen in Phison’s I/O+ firmware. Consistent and sustained reads are the hallmark of optimal DirectStorage performance. We want to avoid peaks and valleys that can cause jitter. Avoiding throttling and smoothing out the response is especially useful with PCIe 4.0 drives in service. I also found that Phison prioritizes host I/O via scheduled background management. Today’s games likely only benefit from load times with low read queue depths, so WD covers all bases with predictive loads.
look carefully
Since we are reviewing the base or bare version of the SN850X, there is only an information label on the front of the drive. Like his previous WD models, this drive is a single-sided drive, which favors compatibility and cooling. The drive’s controller is close to his two packages of M.2 interface, DRAM package, and Flash.
The controller appears to be an updated version of the one found in the SN850. It’s still 8 channels, but with faster flash combined with improved firmware. WD tends to have better firmware, perhaps best exemplified by the SN770. The SN850 performed relatively well with the Phison I/O+ firmware preview and delivered consistent performance. Game Mode 2.0 optimizations should make the SN850X even better, but it’s still too early to judge its applicability for gaming.
The DRAM module is labeled D9XPG. This is Micron’s 16-bit wide 16Gb DDR4 module. This is 2GB of memory, meeting the ideal ratio of DRAM to NAND in the 2TB test sample.
WD updated the BiCS4 found on the SN850 to BiCS5 on this drive. BiCS5 is also on the SN770 and some of the weirder drives include: Sabrent’s 8TB Rocket 4 PlusEach flash package has a capacity of 1 TB and is expected to have 16 dies per package. WD can use 512Gb dies to reduce capacity, but 1Tb dies are needed to keep the drive at 4TB per side. This shows that both the 2 TB and 4 TB SKUs have an ideal total die count of 32 (4 per channel) for peak performance.
BiCS5 didn’t go the way WD and Kioxia originally planned. However, BiCS6 and BiCS+ continue to appear on target, with significant architectural changes to flash. BiCS5 lags behind its competitors, especially in his 176-layer flash from SK hynix and Micron. However, WD has taken full advantage of flash and is able to manage the tradeoffs with a mature architecture.
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