(FIXED) SN850 1TB NVME - slow write speeds (3100) on x570 using M2 Chipset slots (PCH) - confirmed as a problem on MSI, ASRock, Gigabyte and Asus motherboards

WD Support came back and asked for the same things I’d already previously submitted, so SMART results, Firmware revision and bench results. I’ve sent it all back in again.

Ever get the feeling you’re just going around in circles…

WD have now requested my msinfo, which I’ve supplied.

Adding in that I’m seeing the same with my WDS100T1X0E-00AFY0 1TB on an MSI MPG X570 Gaming Pro Carbon WIFI with the latest BIOS.

The WD Dashboard app shows over 800GB free, am on firmware v613000WD and the drive is healthy. I’ve tried with Gaming Mode on/off, but weirdly I can’t run any of the S.M.A.R.T. diagnostics tests, they all just say “Operation failed.”.

I’ve reinstalled with the latest WD drivers, and all my AMD chipset drivers are also up-to-date (as are my Windows Updates, too).

I’m currently running the drive in M2_1 slot, should I be using the _2 slot instead?

It really comes down to your M2 slot configuration. The M2 slots can be Chipset (PCH) or CPU, so you need to determine that first and then ideally use the CPU slot. In my case, using the CPU slot works full speed with the 850.

Funnily enough, I also cannot run the SMART test with the same "Operation Failed " error. I expect its not designed for the 850 and is incompatible in some way. Hilarious how, when they have this info, WD Support still keep asking me to use it…

WD support came back and offered a drive replacement, which obviously won’t fix the problem because the drive works at full speed on the CPU slot and we now have MSI, Asus and ASRock motherboard brands also confirming the limitation on PCH slots and success on CPU slots using their own 850s.

WD support also suggested it was a motherboard issue but provided no further information, such as if they mean my motherboard is faulty. However, again, that can’t be the case if we also have MSI, Asus and ASRock motherboards all confirmed as being affected on their own motherboards, with their own 850s.

Far too many coincidences if the above is true. Far more likely that the consistent factor, the 850 itself, is the responsible party. Which I’ve gone back with.

WD support came back again and offered a very loose and non-committal response. As follows.

Indeed since the drive works as intended in one slot, this means that this should be a firmware issue of the motherboard. We are working on bettering our products and services and this issue has been noted and if any issues are found on our side we will work on releasing a firmware update to fix it. Unfortunately I cannot assist further with this issue as we have not tested our drive with every motherboard model therefore we cannot guarantee that it will be compatible with all the models.

So to me this raises some questions…

  • Why are WD still pursuing this as being a firmware problem on the motherboards, when several brands of motherboards all report the same issue?

  • How many chipset revisions are out there that support GEN4 M2s? I can’t imagine there’s many, so why are they saying they haven’t tested ‘every’ motherboard model? Surely you’d have checked GEN4 motherboards?

I’ve requested a list of supported motherboards that have M2 PCH slot write speeds running to specification. Because now, this all feels like redirection of blame. The consistent factor here is the 850. Not my specific item but the 850 range itself, as seen by MSI and ASRock both testing 850s on x570s and seeing the exact problem.

WD Support came back with the following…

The fact that the drive works with the intended speeds in one of the slots but not the other points out that there is some sort of issue with that specific slot of the motherboard.

You can put the drive in that slot and use WD Dashboard to make sure all settings are up to par.

Furthermore, I can request the compatibility list from our engineering department if you wish, as it is not readily available

So once again, they ignore the confirmation of the problem across several motherboard brands. I have requested a specific list of supported GEN4 motherboards when using a PCH M2 slot and as you can see, apparently that list is not readily available…for some strange reason.

The more this goes around, the more its becoming clear that WD are attempting to cover up a hardware level incompatibly on the SN850.

There are issues with the 850 ssd!
°slower speeds on pch nvme slot
°requirement to reboot on first boot to recognize the drive in BIOS

And WD customer support is a bad joke - simply telling you the motherboard BIOS causes the problem, but why do my other nvme ssd’s work perfectly fine with the bios?


Never had issues with my samsung drives!

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I can confirm that there is a problem with sn850 running on M2 chipset slot PCH of X570 motherboard. I have replaced sn850 with Samsung 980 pro and now I get read speeds 6300 and write 4940. With Wd sn850 I was getting 6300 and 3200. Both drives have the same capacity of 1Tb. Sn850 is now placed on M2 slot running from the CPU lane and is working with published read and write speeds. Motherboard is Gigabyte x570 aorus master. I sure hope that WD will be able to fix the problem with a firmware update because I still have one more sn850 on my third slot that is also running from the chipset and write speed is 3200.

Thanks for the input, so that’s now four brands of motherboards all affected by usage of the 850 on PCH M2 slots, with the exact same throttled write speed problem.

I’ve updated the thread title to reflect.

Well, here’s WD Supports final response, which is interesting for all sorts of reasons…

Unfortunately we do not have such a list to provide to you.

With that being said, we are working with our engineering teams to investigate and resolve this issue swiftly.

We will get back to you as soon as we have an update on the matter

So lets just be clear on this. They cannot provide me with a list of supported x570 chipset motherboards for usage with the SN850 in PCH M2 slots, even though prior comms were blaming me for essentially using the SN850 in a manner (PCH slot) it is not intended to be used in.

This is also after I went back and confirmed that we’re now seeing the same problem across several brands of x570 motherboards and the problem is 100% consistently reproducible.

Well, I just received my SN850 and was eager to check it out, and I quickly saw the issue… 6300mbps-R / 3200~-W. Also x570 Asus Dark Hero and 5900x, plugged a 980 Pro and the problem wasn’t there. After reading all of this thread and some other forums I will have to return this drive and get something else, WD doesn’t seem to be taking this issue seriously so bye bye drive.

same problem with write speed on MSI X570 Unify. Also sometimes whole speed going down to 3.0 even if I switch PCH lanes to Gen4. Will try to refund it.

Dear All,

Root cause is SN850 needs 256bit pcie lane to get high write speeds.

Disable any devices on same pcie bus which are 128bit only and you will see significant increase in write speeds.

I just disabled my Intel WIFI Controller and Titan Ridge thunderbolt controller (which are on same bus and forcing the bus to 128bit) and I am now seeing well over 5GB/s on the writes as the pcie bus is now running at 256bit.

Sadly that’s not correct, or at least not as clear cut.

I have all my motherboard onboard devices disabled and it makes no difference. Will check again though, just to make sure.

Confirmed, all onboard devices disabled and even went through Device Manager and disabled additional stuff like Bluetooth and such. No joy, still capped to 3200.

Might well still have some hard relation to the bus capacity mind. WD have said they’re investigating the issue now, so we’ll see.

Please check in aida64, post screenshot of PCIe bus where your SSD is located.
In the screenshot attached half way down you can see the Maximum payload size on this bus for my motherboard is 128bit and I get low write speeds (3.2Gbps), when I disable Thunderbolt 3 and onboard Wi-Fi (these devices are on same bus as SN850) this max payload then rises to 256bit and I get full write speed (5.3Gbps) on the SSD. This is definitely the cause, so post screenshot of your pcie bus. Hope this helps :slight_smile:

Interesting. How do I pull that report up in Aida?

Sorry, made a mistake, info shows in HWInfo64 :slight_smile:

Thanks but same question, sorry. How do I get that report up?