SN850 only running at PCIe Gen 3?


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

Make sure you are using an AMD CPU that supports PCIe 4.0.
first and second gen Ryzen CPUs have PCIe 3.0 lanes running from the CPU, as well as to the chipset.

3rd gen Ryzen and newer will use PCIe 4.0. (Ryzen 3000 series and Ryzen 5000 series CPUs)

PS even if on 3.0, with a higher end SSD, you will still get the benefits of higher IOPS, faster 4K random reads and writes, and faster write speeds when dealing with TLC NAND which often fails to even saturate PCIe 3.0 when the SLC cache is filled.

Had this same problem with this same board, after hitting brick walls all night I just solved it and am now showing Gen4 speeds. The answer was to download the latest chipset drivers(currently from AMD and not the crappy old ones from Asus. Created an account here to share so hopefully someone else doesn’t have to go through what I did.

Having this exact same issue w/ same mobo. Tried everything. Speeds still capped at 3500-ish mb/s and SN850 being detected as gen3 in the dashboard. Made an account to post this.

Ryzen 3900X
SN850 in m.2_1
Samsung 950 Pro in m.2_2
Strix X570-I
Strix 3080 TI (in gen3 mode due to riser)

Win10 Pro build 19042.1766
SN850 Firmware: 614900WD (latest)
AMD Chipset Driver: (latest)
Bios ver: 4403 (latest)

Tried updating firmware on SSD, tried updating chipset driver to, tried updating bios, tried manually setting the m.2 slot to gen4. No luck.

Is this issue specific to SN850? Open to any suggestions!

Thanks for confirming “SN850 Firmware: 614900WD (latest)”

This was my issue, I was using a 5700G that only supports PCIe 3.0.

I am facing the same issue.
Processor Ryzen 5 5600
Motherboard: B550M Auros Elite rev 1.3
Updated AMD chipset, didn’t work.
Changed every setting in BIOS even bifurcation, still showing connection gen 3 capability gen 4