ASRock Z370 Pro M.2 slots

[samyrt]

I have a ASRock Z370 Pro4 and I just purchased a 970 Evo NMVe SSD. Is there a difference between the two Ultra M.2 slots in terms of speed? I am planning to install the drive into the bottom slot for easier access and to keep the temperatures lower by putting it farther away from the GPU backplate and CPU heatsink.

As far as I can tell, both Ultra M.2 slots are equally as far from the chipset (so there should not be more latency), and according to the manual, they both support PCI-E 3.0 x4. However, I found something on Anandtech that claims that the bottom slot is SATA-only, contradicting what the manual says.

https://www.anandtech.com/show/11860/z370-motherboards-asus-asrock-ecs-evga-biostar-msi-gigabyte/34

Can someone confirm which is true?

Finally, I already have all 6 SATA ports populated, and the manual says:

• 
  If M2_1 is occupied by a SATA-type M.2 device, SATA_5 will be disabled.
  If M2_2 is occupied by a SATA-type M.2 device, SATA_0 will be disabled.

It doesn't say anything explicitly about PCI-E drives, so I am assuming that I will be to use all 6 SATA ports and the Ultra M.2 slots with PCI-E drives at the same time. Again, it will be great if someone can confirm this. For the Extreme4 and Taichi boards, the manual says that the Ultra M.2 slots and SATA ports share lanes, regardless of whether a SATA drive or PCI-E drive is used, so it seems strange that the lower end board would have more connectivity options.

 

[Barty1884]

2 x Ultra M.2 Sockets (M2_1 and M2_2), supports M Key type 2230/2242/2260/2280 M.2 SATA3 6.0 Gb/s module and M.2 PCI Express module up to Gen3 x4 (32 Gb/s)*

https://www.asrock.com/mb/Intel/Z370%20Pro4/index.asp#Specification

Both support PCIe/NVMe drives.... and, as both are via the chipset, there should be absolutely no difference in performance between the two slots.