SN850 Slower than expected performance

Hi All,

Just picked up a SN850 1TB for my new build and i’m getting slower than expected performance.

Asrock X570 ITX/TB3
Ryzen 5950X
RTX 3070 FE
2 x 32GB 3600MHZ

Anyway, just did a fresh install of Windows 10 “19042.782” and have latest drivers installed for chipset, GPU & Windows updates and WD Dashboard, also did the firmware update of SSD to v611110WD.

First thing I have done before installing any games apps etc is test this speed of this new disk and it seems I’m getting lower speeds than most of the reviews I have seen around the web.

Can somebody confirm if these speeds should be better, on the left is my benchmark and on the right are same benchmarks I have seen on review sites; also I doubled checked PCIe is running @4 x4 and it is :

I don’t know why is this happening in my side. I have tried so many thing to resolve this but not possible to solve it.

Support ticket opened with WD: Reference #: 210207-001345

You are sure the motherboard or CPU isn’t the bottleneck? MB is from 2019 as far as I can see, maybe PCIe 4.0 != PCIe 4.0?
Do you have newest BIOS (v3.0 as of this post) etc.? Have you measured other NVME SSDs in the same system and got expected results?


Yes running latest bios for this board which got release a few days ago and CPU is top of the line 5950x. Guru3D review shows that this board is very capable of higher speeds: ASRock X570 Phantom Gaming ITX/TB3 review - Benchmarks: Storage performance

Had a friend come over last night with his drive (same model) and we connected it to my PC, it is working much faster than mine, here is some screen grabs:

My Drive

Friends identical drive:

I’m thinking maybe the controller is bad on mine ?

Very similar issue here, also X570 on a Asus ROG Crosshair Impact VIII in combo with a 5950X, latest BIOS 3204, latest AMD chipset driver 2.13. No issues whatsoever getting it to run in 1st of 2 m2 slots, both BIOS and Windows detected it well, and runs with both MS and a modded Samsung NVMe controller driver. Though on both, same quite disappointing stats, quite close to what ftln94220 is describing

Temps seem ok, better than w/ 980 Pro in direct comparison, and the SN850 also performs better in most scenarios, so almost all good ;o).

One thing I notice here though is the difference of bench between running Crystal v7 and v8. Indeed I can reproduce that in v8, the random tests use different parameters in both versions and thus the stats look different as well. However this doesn’t explain things on the sequential performance.

Any suggestions are welcome, thank you in advance!

Had a friend come over last night with his drive (same model) and we connected it to my PC, it is working much faster than mine, here is some screen grabs:

Why would your friend’s drive attached to your PC work faster if the issue was your controller?

Also: ran ATTO and my stats are very similar to yours there…

Maybe because my drive has a weak controller ?

Also on reddit somebody has 2 identical SN850’s and one of the drives performs worse than the other in the same slot.

I am thinking maybe some duff drives made it through quality control.

Yes I think I saw the same Reddit post… wondered exactly the same thing.

Also saw that apparently “Game Mode” in dashboard should improve the situation. It took ages to find track of the right dashboard version (WD seems to want to cover up the fact that they acquired SanDisk long ago and their whole SSD branch very likely is just that company…) as the latest at least for me didn’t show this option. Now that it does (it apparently disables some lower state energy modes), it didn’t improve my sequential stats but it surely improved the random ones by far. Some of the initial reviews of the SN850 cover this point but it was really tough to find more evidence.

Ultimately, yes I agree, it might just be some clumsy samples in a clumsy batch we got.
Maybe time for a return/refund.

I have a ticket open with WD #: 210207-001345, at the moment I am speaking with a low level support guy, hopefully I will get somebody with a bit more knowledge in the coming days.

@ftln94220 - resolved my issues: a combination of which slot to use, BIOS settings for that (Gen4/Auto), as well as having had bad luck with the drive itself - got another one and that one performed much better. I hope WD will resolve this for and with you, but I just wasn’t patient enough so initiated a return. Good luck!

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Hi Davy-Dee,

I have requested RMA from WD: Reference #: 210207-001345

Problem is the RMA is portal is down and the tech support guy on my ticket just told me to wait a couple of weeks to see if it comes back up before we can request the RMA:

As I am running ITX and I only have one M.2 slot and its lanes use the CPU then I cant really get it wrong. In bios everything is configured correctly, Gen4 with X4 Link Speed.


Did you test with the latest [BIOS for your board]ASRock > X570 Phantom Gaming-ITX/TB3)? In my research I came a lot of issues from others around that, and Asrock has a version as recent as Feb 5, 2021. If you didn’t try it this might help, apart from just the drive possibly being faulty.

Another thing I noticed is some strange wiring on some boards where some PCIe lanes provide bottle neck in some conditions. Now, your board doesn’t have so many options for PCIe usage - however you do use X570 AND a 4.0 RTX 3070 which in fact is PCIe 4.0 capable. When I quickly reviewed the manual for your Phantom board I noticed something strange - there is a mentioning of a “PCIe riser card” which would provide v4.0 PCIe… could it be, that in fact besides the PCIe x16 for the GPU the NVMe slot is only Gen 3? Probably not, as you likely have done thorough review of all those factors.


PS/Edit: in the past I had good experience with WD RMAs, but these days I just go thru the vendor.

Hi Davy-Dee,
Been running the new V3.0 Bios since release day and it didn’t improve anything.
PCI-E riser in the manual is talking about splitting the single x16 slot ( PCI-e bifurcation explained – Don’s Blog ( which I don’t use. The M.2 slot on the back is the one I am using and its showing in WD Dashboard as Gen4 x4 so no issues there.

I just wish I had access to a debug driver so I could check through the logs.

I came to WD because of the all the good reviews, but all I see around the web is people having issue with this drive.

It could be just bad luck and I got a fluffy drive.

Edit: just did a complete reset cmos and reflash of bios, just in case but still hitting the wall: