WD Black SN850X 1TB

WD gives its top SSD some added X-factor

- JEREMY LAIRD

WD’S BLACK SN850 was one of our favorite PCIe Gen 4 drives. So, this new SN850X model is certainly intriguing. What it’s not, to be clear, is a fancy new PCIe Gen 5 drive. If that’s disappointing, the reality is that there’s barely any support for PCIe 5 storage right now. Yes, Intel’s Alder Lake CPU family has limited PCIe 5 support, it doesn’t have dedicated lanes for storage, so it all gets a bit complicated. Meanwhile, AMD’s new Ryzen 7000 chips have proper PCIe 5 storage support, but they have only just been announced.

With that PCIe 5 digression dealt with, what to make of this SSD, likely one of the last of the high-end PCIe 4 generation? As before, it’s a quad-lane PCIe Gen 4 M.2 drive, this time with an updated version of WD’s in-house controller chip, albeit there are no details on exactly how the new controller has been improved.

The new 'X' model reviewed here starts at 1TB and goes all the way to 4TB. The old non-X kicked off at 512GB and topped out at 2TB. The drive’s NAND flash chips have been upgraded from 96-layer TLC chips to newer 112-layer items. WD isn’t quoting specific improvements from the chips, but typically new-gen NAND flash improves on throughput and latency.

Comparing this 1TB model with its direct progenitor, however, overall drive performance is up. Claimed write speeds have edged from 7,000MB/s to 7,300MB/s, while reads leap from 5,300MB/s to 6,300MB/s. As for IOPS performance, the old 1TB drive clocked in at 1M reads and 720K writes. WD has bumped those to 1.1M and 800K respectively.