Enthusiasts who are using Western Digital’s WD Black SN850 NVMe SSDs on AMD X570 motherboards should ensure that they’re installed on an M.2 slot that’s linked to the Ryzen processor rather than the chipset. According to benchmarks conducted by ComputerBase (and growing complaints from owners), WD Black SN850 NVMe SSDs suffer a major performance hit of over 40 percent when they’re paired with an M.2 port that’s connected to the latter. While there’s typically a difference in performance between M.2 slots connected to the processor and those connected to the chipset, the performance degradation exhibited by WD Black SN850 NVMe SSDs goes way beyond what’s typical and expected (less than 10 percent). Western Digital is looking into the issue.
Due to the limited PCIe lanes on processors, not every M.2 port communicates directly with the chip. Some M.2 slots are connected to the chipset instead. In the case of AMD’s X570 motherboards, it’s public knowledge that there is a performance disparity between chipset-and processor-based M.2 slots. This is due to the higher latency on the former.
Sources: ComputerBase, Tom’s Hardware