(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

I have no idea what that view is, I’m on the same version of HWINFO, v7.04-4480 and all I have is either a Sensor Status view or a Summary View, as per below.


Do you have a paid version or something? Pro maybe?

Just uncheck boxes on startup and press « run »

Well, that’s about as intuitive as something not very intuitive! But it works!

Right, so what I can see is that one of my PCI Buses has a Max Payload of 128bytes but all the devices on that bus that I can disable, such as onboard audio, has been disabled. The rest, like USB hubs just aren’t an option to disable.

SN850 on M2_3 (CPU)

SN850 on M2_1 (PCH)

So, yes, this appears to bear out that the PCH M2 slots, sharing devices on the chipset, is limiting bandwidth and that being the case, no wonder WD have no comment to make. Because this is a fundamental hardware incompatibility to PCH M2 slots, if the core design requires a Max Payload of double that which is being set.

Which device on the bus is making the whole bus run at 128byte?

Looks like there are several on there. USB controllers, Audio, the LAN controllers, SATA controller. Quite the collection of onboard devices on that PCI Bus on the MSI Meg x570 it seems.

I have a Samsung Pro 1TB NVME on M2_2, also PCH, and that’s quite happily chugging away at 256 bytes. However, interestingly, I previously had a Samsung Pro 500GB on M2_1, just like my current SN850 is on M2_1 and that was running at the full write speeds, with no other change to my system around devices being disabled/changed, indicating that the SN850 appears, like you say, to need less other devices on the bus in order to be effective.

I do have a WD SN750 and it has the exact same problem with MSI B550i Gaming motherboard.

I am using the drive in the second M2 slot (PCH) and it shows only write speed of only 1100 mbps vs read speed of 3400. The MPS/Maximum Payload is only 128.

When I follow your suggestion and disable the built-in WIFI and Bluetooth, the MPS increases to 256 and with it the write speed of the SN750 increases to 3400. Too bad I need the WIFI and Bluetooth.

I hope WD is aware of this, and the same firmware fix they are providing now for the SN850 will also be provided for the SN750.

I’ve managed to resolve this by upgrading my CPU - going from a Ryzen 1600 to a 5600X more than doubled my read rates, and dropped latency to almost a third of what it had been. I only noticed this because my NVIDIA RTX 3070 was running on PCI-e 3 not PCI-4.

It might not work for anyone, but it’s worth checking what HWInfo64 says as the maximum payload size on your PCI-e (mine was 128bit before, and now it’s 256bit)

Sadly it’s not that for me, you can see in the screenshot above that 512 is what the bus is capable of but the 850 is capped to 128. Ryzen 5950x CPU.

I also hope WD will issue a new FW for SN750. Using it on M2B(chipset) slot and got same write speed as u at ~1100mbps. I’m using Gigabyte X570 Pro Wifi.

Any official news on the FW for SN750 regarding this?

Looks like a firmware update is on the way, potentially as soon as tomorrow!

Thanks to ftln94220, I supplied all the info regarding the payload limitation onto my support ticket.

Edit: Firmware update available now and write speeds are now at almost 5000mb! Looks like it did the trick and the CPU lane M2 install continues to operate as it did before too. The firmware seems to have also bumped up the Random IOPS a fair chunk too.


I have two SN850’s in BIOS RAID0 on my ASRock Creator X570 board, I’m not sure the dashboard can pick up the devices, please see attached:

OK i have this same issue, but I can’t run the dashboard…which appears to be required to download and install the Firmware to fix the SN850 drives…

Mon Jul 12 17:25:19 2021 0x7bc10 Critical: – js: “Chroma connection FAILED FILE_NOT_FOUND”
Mon Jul 12 17:25:19 2021 0x7bc10 Critical: – js: “Uncaught (in promise) #”

anyone recognize this missing file error? reinstalling, running as admin etc. doesn’t help get past “Loading…” on the Dashboard. I found these errors in the text file in the install dir C:\Program Files (x86)\Western Digital\SSD Dashboard

No idea what’s going on there, its possible that the array is stopping the Firmware in some way, perhaps you need to break the array, apply the Firmware then rebuild the array?

Sounds like the installer is broken to me, you could try uninstalling, cleaning up any remnants manually then redownloading and installing again?

I’ve never had any problems with the WD Dashboard like the ones youre seeing.

Anyway to get the firmware without the WD Dashboard since i obviously cant install it? Tried uninstall/reinstall with rebooting in-between as well

The array is my main boot drive, I can’t break it.

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Not sure, there may be a CLI if you can grab the file from somewhere but I’ve never done it that way before. Sorry.

Doesn’t make sense that the array would break the ability to update the Firmware but the dashboard screenshot does appear to indicate that it can’t detect the NVMEs individually :frowning:

Your only option may be to move the 850s to a different PC, secondary to the OS drive and update that way, or worst case backup your OS drive, remove the NVME arrays, redeploy the image to a new SSD, boot into that and then check if the dashboard can see the individual 850s. Macrium is good for backups.

So, I disabled WIFI6 as mentioned above and it does instead of 128 bit,… 256bit… getting these speeds now. not sure if i should continue to fuss with trying to update firmware/ get ‘dashboard’ to work or is this the max speed i will get either way?

Updated speed w/ wifi6 disabled @ 256-bit

Original speed @ 128-bit

will updating the firmware allow users to keep WIFI enabled and get the full 512 bit throughput?