SN850X Slow Performance - 1770 MB/s

My SN 850X 1TB configured as system drive is performing way below the expectation with a pathetic read speed of 1750 MBPS where itis supposed to perform near 7000 MBps.


I have windows 11 with 32GB of RAM running on ASUS Z270E MB with i7 7th Gen.

The WD dashboard software has already installed the latest firmware for the SSD.

Any help / guidance on the fix is appreciated

Hi @berlstone,

Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting:

Check the dashboard application and check if the SSD is using 4 PCIe lanes. Speeds like that are more common with drives running with 2 lanes.

Beyond that, use hwinfo64 to check if the drive is using a lower than normal payload size.
Free Download HWiNFO Sofware | Installer & Portable for Windows, DOS (the portable version is preferred)
To check the payload size, after launching the application, click on Drives > NVMe Drives > Select your WD Black SN850X> Then click on the blue text next to “Host Controller”.
The SSD on your system should use a payload size of 256 or 512 bytes (the max the drive supports is 512 bytes, though that requires a PCIe 4.0 slot to notice any benefit), Under PCIe 3.0 it should be 256 or higher.

If it is using 128 bytes, then you will notice large slowdowns, especially on PCIe 3.0.