eGPU Restart Woes With Catalina

I'm impressed that Apple found it useful to recommend or semi-support eGPU's with Mac Mini. However, I'm not impressed that Apple doesn't seem to have tested this compatibility with Catalina. It's simply put...broken. Either it wasn't tested in Beta or reported and found unimportant enough for investigation. Or, it was tested once and broken along the way.

Any way you look at this, it's a failure and at the very least should be addressed. Using an eGPU was one of the primary reasons I bought the Mac Mini, since the Intel UHD 630 integrated graphics taxes the CPU too much, even for basic graphics. Apple has multiple documents online regarding the eGPU capability but none of the documentation address the problems users are seeing. You only need to Google Search, "eGPU issue Catalina" to quickly see those complaints.

Restarts are the biggest gripe. When you restart with the eGPU active, unless you have another monitor connected to the Mac Mini's own HDMI port, you'll see nothing upon reboot. Even so, if you do have a monitor plugged in there with the eGPU connected, as soon as you log on to the Mac, it freezes. The only resolution here is a hard-boot.

I've tried a myriad of workarounds, including a dummy HDMI plug, but none have worked. AppleCare suggested the Mac mini hardware was bad, which I feel is a typical problem to buy time. I felt I could troubleshoot this faster, myself.

In the meantime, here's a procedure I use to help my situation. My setup is a 65" 4K TV and a 4K 32-inch Monoprice monitor. These are powered by a Gigabyte RadeonRX 570 inside a Sonnet eGFX Breakaway Box 550W.

1. Be sure you have a monitor plugged into the Mac Mini's HDMI port. Using a second HDMI cable into my TV works fine, using the TV as an HDMI switcher.
2. Before rebooting, in the upper right, select the eGPU icon, click it and select Disconnect eGPU.
3. Make sure the mini's main HDMI monitor is up and showing the desktop.
4. Power off the eGPU.
5. Restart the mini.
6. Log back in to the mini when it comes up.
7. After the OS fully loads and is idle, power on the eGPU and switch the monitor back to using that.

NOTE You will need to leave the HDMI setup in place indefinitely, or be prone to monitor Arrangement frustrations upon each restart.

I do wish Apple would do one of three things: A) fix the eGPU reboot issue, because it appears to be the OS or firmware, B) Acknowledge it's very limited support, or C) Just increase the size of the mini to hold a better GPU, give it a display port, and call is simply.....

Mac.