1 Solution
I have your answer, and you will not like it 
I suggest making sure that you have your power button option set to shut down your PC incase your screen vanishes like mine has before you turn off your PC. Then you need to pull your 4x PCIE card, turn your PC on, problem gone, put card back, problem comes back.!
I know this because I have (this gets confusing fast) 2x, PCIE 2 x2 cards each providing me with 4x SATA ports, I also have 2x separate PCIE x1 NIC's.
I first discovered this after building my new server using the Ryzen 2200G and the ASRock AB350 PRO4 motherboard.
My testing, 1 of the PCIE x2 storage crads in euither of the (physical PCIE x16) slots and I get a screen bifurcation, followed by the right side going to the solid desktop colour and then the left side screwing up, it did this on a clean fresh W10 x64 Home N (EU version) install with drivers from the CD, as well as from a fullupgraded W10 using Windows installed drivers.
Putting the storage cards in and out (for testing) didn't seem to wreck the OS and likewise the add-in NIC's. I also have an old x4 PCIE2 "RAID" controller (glorified software RAID) that served me well (now retired but known to function as I used it last week), a Highpoint RocketRaid 2320, also did the same thing.! Interestingly, the screen screwed up once when I was moving data across the network, the server continued to function correctly, just without any display.
I found this thread whilst looking for PCIE lane bifurcation and whether Ryzen supports PCIE 2x cards at all.? Now it looks like it might be x4 cards as well, AND / OR both the ASRock AB350M-PRO4 and the AB350-PRO4. Or even the new Ryzen APU's.! more on that... The last thing I did on this build was to try and upgrade the BIOS / UEFI and it reccomendd going back to an older version...... so a short while later I ordered the cheapest AM4 CPU with graphics I could, so I can then upgrade the BIOS / UEFI to one in which my Ryzen 2200G will function (I had to pull my 1700X from my main PC to get this mobo up and running and I will spend £45 to not have to do that again!).
So I now have a new AMD A6-9500 APU on its way, which I will first and foremost test with the above mention cards and build, I will report back sometime tomorrow evening UK time.
I have your answer, and you will not like it
I suggest making sure that you have your power button option set to shut down your PC incase your screen vanishes like mine has before you turn off your PC. Then you need to pull your 4x PCIE card, turn your PC on, problem gone, put card back, problem comes back.!
I know this because I have (this gets confusing fast) 2x, PCIE 2 x2 cards each providing me with 4x SATA ports, I also have 2x separate PCIE x1 NIC's.
I first discovered this after building my new server using the Ryzen 2200G and the ASRock AB350 PRO4 motherboard.
My testing, 1 of the PCIE x2 storage crads in euither of the (physical PCIE x16) slots and I get a screen bifurcation, followed by the right side going to the solid desktop colour and then the left side screwing up, it did this on a clean fresh W10 x64 Home N (EU version) install with drivers from the CD, as well as from a fullupgraded W10 using Windows installed drivers.
Putting the storage cards in and out (for testing) didn't seem to wreck the OS and likewise the add-in NIC's. I also have an old x4 PCIE2 "RAID" controller (glorified software RAID) that served me well (now retired but known to function as I used it last week), a Highpoint RocketRaid 2320, also did the same thing.! Interestingly, the screen screwed up once when I was moving data across the network, the server continued to function correctly, just without any display.
I found this thread whilst looking for PCIE lane bifurcation and whether Ryzen supports PCIE 2x cards at all.? Now it looks like it might be x4 cards as well, AND / OR both the ASRock AB350M-PRO4 and the AB350-PRO4. Or even the new Ryzen APU's.! more on that... The last thing I did on this build was to try and upgrade the BIOS / UEFI and it reccomendd going back to an older version...... so a short while later I ordered the cheapest AM4 CPU with graphics I could, so I can then upgrade the BIOS / UEFI to one in which my Ryzen 2200G will function (I had to pull my 1700X from my main PC to get this mobo up and running and I will spend £45 to not have to do that again!).
So I now have a new AMD A6-9500 APU on its way, which I will first and foremost test with the above mention cards and build, I will report back sometime tomorrow evening UK time.
Thanks for your feedback and confirmation of my fear that this system will simply not function as expected...
The fault can only be with AMD or ASRock.! I am strongly leaning towards AMD.
FYI, my new CPU being delivered today.... will arrive sometime tomorrow so I can not say whether this is a ZEN issue or an AM4 issue. Currently very unhappy
I believe I have a BIOS option change that has fixed the issue with my 2200G and all cards installed, and zero software changes or other changes bar the swap back to the ZEN CPU.
Need to test all cards, reboot a few times and of course relay to you the BIOS / UEFI changes that I made (I was testing 1 at a time), so I am pretty confident "pre-testing" that I have found a working fix.
UPDATE: It seems that the BIOS / UEFI fix has worked for me, I cant log in at the moment to find out exactly what and where the changes need to be made.
Roughly, they are in Advanced > sub menu > PCIE settings for CPU and SB. I set both to run at PCIE 2.0 (other options are PCIE 1.0 and (AUTO, which is the default).
Problem fixed on a reboot 
I have the same exact issue on an Asrock x370 fatality itx/ac motherboard with a 2400G CPU. BIOS version is 4.60 and all settings are left untouched (by default)
The card I am plugging on the PCI-E port is a Revodrive 3 X2 240GB SSD (which runs at PCI-E 2.0 x4). SSD is showing up fine and can be accessed.
I haven't tried the workarounds in this thread yet but looks like there's a working solution (will try later when I have access to the machine). It would be nice if asrock (sounds like a motherboard issue) could fix it without having people mess with their BIOS settings though.
I had exactly the same issue on a Gigabyte Motherboard: Solution: Disabled CSM Support.
Worked flawless.
