Indecisive Mac - Can’t cleanly boot into both macOS and Windows
Mac mini 2018 (FileVault OFF)
macOS 11 Public Beta
Sapphire Nitro+ RX 580 4GB
Sonnet 350W eGFX Breakaway Box
2 Monitors: 1 DisplayPort 1080p, 1 DVI → HDMI 1024p
Windows will only finishing booting if both displays are plugged into the RX 580. If the HDMI is in the Mac, the Windows logo cycles indefinitely and never reaches the spinning circles.
I don’t particularly care which is which, as long as I can just leave it because the box & Mac mini at behind my monitor and are hard to reach.
I do also have a Devil Box that I found cheap on the way to do testing with as well.
I do know I’m running the public beta, but it’s largely stable, and I’ve seen reports of similar issues on Catalina as well.
Are you running both OS off the internal SSD?
Below is what works with my setup in 10.15.6. You might try it with the Big Sur Beta.
Shut down in Mac OS. Unplug the eGPU and any other TB3 devices.
Keep the HDMI cable attached between the Mini and one display.
Unplug the display cable from your eGPU.
Start-up and sign in to the Mac OS desktop.
Hot plug your eGPU (with no display cables attached) into the Mini.
Confirm your eGPU is recognized by Mac OS, and then shut down.
Disconnect the HDMI cable from the Mini. Connect both displays to your eGPU.
Restart and wait (with black screens) for the minute or so Mac OS takes to boot up and appear on your displays. You can hot plug any additional TB devices such as external storage.
After those steps, Catalina “remembers” the setup, and boots up normally in Mac OS, and boots into Windows normally as well - with no unplugging and replugging of displays.
@mini-i5, Followed your instructions, unfortunately ten minutes later I am still waiting to get into macOS after booting with both monitors in the eGPU.
I even force restarted the Mac to give it another chance to boot up. No picture.
Can't quite picture your setup, but the first reboot into macOS from Windows seems to be problematic for me as well. All other reboots work fine.
It seems you can engage the iGPU by having that HDMI cable plugged in (which is apparently the opposite of how Windows likes to boot), but my solution is to just turn my Razer Core X on and off at the switch when I get black screens when rebooting from Windows into macOS. This is basically just like hot-plugging, and immediately wakes the monitors up. Because I'm not yet in the OS properly, I don't get any disconnection warnings (and presume this is pretty harmless).
I understand that you might not be able to access the Sonnet power, or the TB3 cable to do this, but maybe you can access a switch on the power point for the Sonnet? Bit janky, but should get the job done.
@prototofu, I suppose, but honestly the idea here is that the eGPU on macOS should be plug-and-play. The only reason I’m here is because my software is beta so I can’t call Apple. I guess I’ll just be waiting until Big Sur is out of beta and contacting Apple. Because there is no reason that I can’t have both monitors in the eGPU and boot into macOS.