I have identical 2TB Samsung 970 EVO M.2 NVMe drives in each of the sockets (PM1 and PM2) and 2 SATA SSD's in my rig. The top 16x slot has a graphics card in it but other than that i have no other cards in the PCIe slots. Yet for some reason if i activate RAID mode and enable PCIe RAID, only PM1 seems to show up as VROC capable. The M2 drive in socket PM2 shows up next to the SATA drives in the RST menu. The mobo thinks the 2nd Samsung 970 EVO is a SATA drive. I even have both PM1 and PM2 set as VMD2 yet only the drive in PM1 shows up in the VMD menu. Bear in mind i'm using the Intel i7 9800X CPU which has 44 lanes.
 




As we see from the manual, it clearly states that if nothing is in PCIe slot 6 then the PM2 M2 slot should get x4 lanes from the CPU. But it is clearly getting x4 lanes from the PCH even when PCIe slot 6 isn't populated. Otherwise it would not show up as a SATA drive when RAID/PCIe RAID is enabled.

GGTV-Jon
In the first picture with the 1 NVME and the SATA drives it is still listed as an PCIe device, looks like it is listing the drives that are available for raid in the bios.
 
I do have a question about how this is supposed to work in this situation. I have done raid setups but that (I actually need to work on my server today - drive swap time) is with actual raid cards / hardware raid in a Linux environment.
 
Are you supposed to setup the actual array in bios or just set the ability for raid in bios but build it in the OS for a software type raid?
 
My other question is is Intel liming the ability for booting from raid?

Bootable RAID 0 via VROC is the plan. But even if i get 2x Intel M2 SSD's, if PM1 and PM2 are not both going through the CPU's VMD controller even that won't work. The only way to do it would be to put a couple of intel M2 NVMe drives into a Asus AIC so that they'd both definitely be on the VMD controller. 

GGTV-Jon
Bottom pf page 22 in the PDF -
 

24. VROC Header
VROC stands for Virtual RAID On CPU. The VROC header works in conjunction with PCIe SSDs. The header is used to provide an Intel® hardware key that will unlock advanced RAID functions, such as RAID5. SATA RAID does not require a VROC key.
At the time of print, VROC will work with many SSDs, but is only bootable with Intel® SSDs. VROC is only compatible with Core™ X-series Skylake-X CPUs.

 
I thought in that documentation from Intel (unless it has been revised again) that bootable raid was limited

Only limited because not many SSD's are supported. But mostly limited because two M2 NVMe SSD's absolutely must be on the same VMD controller for them to be able to be paired up (even Intel ones). So the only way to do it on this board it seems, is to put a couple of intel m2's in a Asus Hyper card and putting it in one of the x16 slots so that both M2's or on the same VMD controller.
 
Personally i have two Angelbird PX1 add in cards. When i put each of my M2's into the angelbirds and put them in PCIe slots 3 and 4 (which both share the same VMD) then and only then do they show up in the VROC menu together to be RAID'd. But yeah... unfortunately the Samsung 970's are unsupported by RAID. I'm willing to be the Intel SSD's would work fine though if they were put in the Angelbirds in PCIe sockets 3 and 4. 
 
It's still really annoying though, that socket PM2 isn't part of any of the CPU's VMD controllers when according to the manual, it looks like it should belong to VMD2. Even the VROC FAQ page makes it look like the PM2 socket it can be configured to the VMD2 controller. But it quite clearly is not because it shows up in the mobo settings as being grouped in with the SATA controller. Which means its running through the PCH (even when PCIe slot 6 isn't populated).