I have a WD black SN850 500GB in my M.2_1 slot on my ASUS ROG Strix x570i mobo. The only thing I can find in bios is set to M.2_1 link = Gen 4. Yet the SSD is still running at Gen 3 according Dashboard (Capability: Gen 4, Connection: Gen 3). I have the latest non-beta bios (ver 3603). Is there something I’m missing to enable Gen 4. My crystal diskmark is 3770MB/s, so it’s half its rated Gen 4 speed.
First thing is to makes sure the BIOS is set to auto for PCIE speed and not set to x3.
If it is, sad to say but you may be being throttled by the devices you have attached. For example, having SATA SSDs in certain slots can drop the available bandwidth of PCIE.
Also, what is the slot type for your M2_1? CPU or PCH (chipset)? If its PCH, try swapping out to a CPU slot.
May I ask if you could solve this? I am having the same issue on a B550 with a Zen3 CPU, SN850 is in the upper slot and should connect to the CPU directly, so the connection should be Gen4, but it is Gen3.
Having same issue on B550-A Pro Motherboard. SN850 only running at Gen3, cant get Gen4 enabled for the life of me. I found the issue in my case is I am running a 5700G which does not support Gen4. Here is a good forum post on the topic. 5700G, X570, and PCIe 4.0 - CPUs, Motherboards, and Memory - Linus Tech Tips