2018 Mac Mini [8th,6C,B] + RX 5700 XT @ 32Gbps-TB3 (Sonnet Breakaway 650) + macOS 10.15.5 & Win10 2004 [yeloshak]  

System specs 

MacOS Catalina 10.15.5, latest bootcamp drivers

Windows 10 Home, latest 2004, 19041.264

AMD adrenalin, 20.5.1 

(all versions from end of may 2020 updates (no special versions / mods))

MacMini 2020, 6c i7-8700B 3.2GHz, 64GB / 1T

BootCamp on EXTERNAL USB Corsair flash voyager GTX256GB https://www.amazon.com/gp/product/B079NWJTGG  

(the USB SSD blocks both USB holes on the MacMini, but I use an anker USBC hub in port by HDMI port)

LG 34WK95C-W (34” wide at 3440x1440 and HDMI cable, works great with PBP modes on display)

eGPU hardware

PowerColor RedDevil RX 5700 XT

Sonnet Breakaway 650 in TB3 port next to ethernet port

TB3 cable that came with Sonnet

Hardware pictures 

2 boxes and a big curved display, a couple cords.

Installation steps 

Goal:

of this build was a fast stable Mac (im done with Hackintosh) with FAST graphics and an occasional gaming PC for those Win only games. I want to be able to keep it up to date on versions / drivers using the normal channels, not hacks. I killed my last MacBook by only using it as a desktop so I went mini this time. Also all of this HW goes in the closet with 2m cables and only the display and KB on my desktop (happy wife)

Notes:

So this took about 5 days to figure out but in the end it was quite simple. The walk through looks worse than it is. I do want to thank everyone on this board for all the great details that made it possible to figure this out.  Im going with LOTS of detail and links in this write up trying to save fellow noobs a few days of reading and correlating all the good posts out there to their specific build/needs. 

I used an external USB SSD for my windows install. I can imagine how this might be easier on an internal SSD partition using bootcamp assistant to install windows. I used wintoUSB paid version to accomplish this and found it easy and stable.

Both times in this setup I installed windows10 home

Important: this setup has only 1 display in windows, and only using the eGPU and not the iGPU (obviously). There are probably some steps to get both working, but I think thats the hard part. I am fine with just one display. Maybe this is why the MacBook installs are so hard - you can’t just unplug the internal display. Here you just leave the HDMI port empty and iGPU is disabled and frees up resources for the eGPU. 

I had to install Windows10 twice to get the working pci.sys from the old version of Windows10. Maybe someone should just post the working pci.sys from 1903... 

You need VMware fusion or another PC for creating/editing the USB SSD.

The install:

get the old (May 2019) Win10 1903 iso using a Windows ISO DL tool from (example: heidoc.com) 

install 1903 on SSD. I used WintoUSB https://www.easyuefi.com/wintousb/ and followed this walk through: https://www.imore.com/how-install-windows-10-your-mac-mini-external-drive  

When complete, in fusion grab the c:\windows\system32\drivers\pci.sys (dont need to even boot this OS!)

name it pci-1903.sys and keep it handy.

then install latest Windows10 ISO 

DL from Microsoft : https://www.microsoft.com/en-us/software-download/windows10ISO  

use VMware fusion to prep the SSD and wintousb to install. I did the whole process again to be clean: https://www.imore.com/how-install-windows-10-your-mac-mini-external-drive  

Launch Boot Camp Assistant in MacOS and download windows support software from Action menu and copy it to the SSD c: drive

boot Mac into recovery (hold CMD-R on startup), use startup security util (menu item) to disable OS signing and allow booting from USB drives. I enabled the FW password because it pauses on boot to let you select drive and I found this handy in my troubleshooting. Make the password simple. Or boot with option key down to select drive

shutdown

boot into bootcamp windows (dont connect eGPU!) and finish installation

run the bootcamp setup from windows support software folder you copied onto the C: drive. If the installer gets stuck on enumerating preinstall files (it always did for me) then

run a command window (cmd) as administrator 

cd windows support\BootCamp\Drivers\Apple

msiexec /i BootCamp.msi

restart

run apple SW update from start menu and let it update to latest boot camp drivers

use bootcamp in tray to select windows as startup disk (Note: I am not seeing windows as choice in Mac or Mac as a choice in windows)

just to be safe, lets prevent automatic SW updates in windows to prevent unexpected bricking.

stop updates - https://egpu.io/forums/pc-setup/egpu-fail-after-update-to-windows-19-03/  

Win10 Home you need to add gpeeditor: https://www.itechtics.com/enable-gpedit-windows-10-home/  

download driver for radeon card from AMD https://www.amd.com/en/support  

plug in eGPU, turn it on, should be detected and windows installs generic VGA driver

check in device manager (right click windows start / logo) and should appear as AMD RX5700XT in display adapters but with code 12 error. This is apparently caused by the internal iGPU on HDMI taking too many resources.

run the radeon installer - it should detect graphics card and install but then errors at the end because of our code 12. Its OK, drivers did get installed. 

shutdown and boot back to Mac (I remove USB SSD and mini will boot to macOS by itself)

using VMfusion or NTFS drive access, insert USB SSD and on your bootcamp C: partition take ownership of pci.sys and the drivers folder:  https://www.laptopmag.com/articles/take-ownership-folder-windows-10-using-file-explorer  

open directory c:\windows\system32\drivers\

rename pci.sys to pci-2004.sys

copy pci-1903.sys to c:\windows\system32\drivers\ then duplicate it and rename it pci.sys

shutdown

connect eGPU to TB3 port, connect monitor to eGPU graphics card port and no displays to any Mac ports! 

boot (blind on my machine) with eGPU on

I need to enter FW password and hit return and then to select the EFI partition on USB to boot (up arrow, then right arrow, then return)

I see my USB SSD light start flashing and then it should display windows login OK and you're done.

After this things just worked. It sleeps, it reboots, it runs games FAST - Im happy. 

that was it for now - lets see what happens when time to update but should be good for a while

Benchmarks 

Happy to run - need to know what you guys want to see

Comments 

Yeloshak