Asus Prime X370 Pro Nvme Support

Six of the SATA ports are from the chipset, two are from the CPU. However, if you utilize an M.2 NVMe drive, the two SATA ports from the CPU are disabled.

That is non what I'k seeing in the Windows Device Director.

Perhaps what you say applies for B350, simply not for X370.

As seen in my screenshot it's very clear that 8 ACTIVE SATA connections 7 HDD + 1 SSD are all linked to the same AHCI 1.0 Serial ATA Controller which has the ID:
Vendor 1022 Device 43B5 (PCI bus 1, device 0, function 1)
https://devicehunt.com/view/type/pci/vendor/1022/device/43B5 - X370 Series Chipset SATA Controller

Again, I repeat, I have 8 storage devices ALL linked to this X370 SATA Controller, which means the information posted on the link above from ASUS is plain wrong. (Information technology says merely 6 SATA ports for X370)

The "other" port which is not connected anywhere right now is on a completely different PCI-to-PCI bridge (I'm guessing Within the Ryzen 7 CPU), and is named AMD SATA Controller, with the ID:
Vendor 1022 Device 7901 (PCI passenger vehicle 11, device 0, function two)
https://devicehunt.com/view/type/pci/vendor/1022/device/7901 - FCH SATA Controller [AHCI mode]

It's quite clear that these are two dissimilar controllers, and past looking at that schematic, 7901 is the dual-port SATA controller Inside the CPU.
(And on my particular lath I have a strong feeling information technology'due south linked directly to that Grand.2 slot - unfortunately I cannot shut down the computer and take out the board to follow the traces), only given the fact that it's correct under the CPU, there'due south a very strong chance that is the example:

Volition test this in nearly a week when my Grand.2 SATA drive arrives (within a laptop actually, which I'm going to excerpt and replace with a properly sized NVMe drive).

A few more than screenshots: