2015 13" Macbook Pro Retina [5th,2C,U] + RX 570 @ 16Gbps-TB2>TB3 (PowerColor Mini Pro) + Win10
2015 13" Macbook Pro Retina
2.7Ghz Intel i5-5257U
iGPU Intel Iris 6100
Windows 10 1909
MacOS on El captain, but not using it with eGPU
Apple TB3 to TB2 adapter
Apple 0.5m Thunderbolt 2 cable
Started with an old Windows 10 1607 installation
Updated all bootcamp drivers
Installed all pending windows updates (now on 1909, build 18363.720)
At this point I could hotplug the eGPU and it would be detected, but would not work due to code/error 12. It turns out this issue started after a certain 1903 build and isn't fixed in 1909.
Disabled Windows updates (This is to prevent windows downloading drivers automatically)
Downloaded and ran DDU in Safemode to remove all AMD graphics drivers
Took ownership of pci.sys, rename to pci.sys.bak, then put older version (1903 V1) in its place
Hotplug the eGPU and wait for it to be detected. Then installed the latest official AMD drivers (March 5 2020). It ended in an error, but the drivers were still installed.
Restarted, and found that pci.sys was replaced with the a new version, so I redid the step earlier and replaced with older pci.sys
Restarted again and tried hotpugging eGPU but it didn't get detected
Restarted while holding option key. hotplugged eGPU then chose Windows/Bootcamp
Now it works if I start it up this way
This isn't everything I tried to get it working, but these were the steps that seemed to actually be effective in my case. There is a lot of info scattered all over the forums, but the key takeaway is that Windows 10 1909 will NOT work with the eGPU no matter what other tricks you try because of the pci.sys file. There are other posts out there that have a more detailed guide on replacing that file. I had some BSODs along the way as well but keep trying and it should eventually work.
Extra: For those interested in the PowerColor Mini Pro/VisionTek Mini eGFX, I found the included fan to be quite annoying over time. Its not super loud, but it runs at an annoying pitch. I went on Ebay and found a $5 replacement fan that is 0.03A lower power draw(Original is 12V 0.18A), sleeve bearing instead of double ball bearing, and its much better now in my opinion. The fan dimensions are 80x80x10mm.
Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts