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macrumors regular
Original poster
Jun 11, 2017
San Diego, California

I have a Mac mini 2018 , with a Sonnet Breakout Box 550. In the Box is an AMD RX 580.

In Mojave, I would boot the Mac partition, and only connect the RX 580 to the monitor. after login, I had full acceleration and was truly plug and play. I never plugged in the HDMI cable to the Intel GPU.

In Catalina, the Mac would not boot to complete the install without the built in Intel GPU connected. It just kept shutting down. When the Mac finally booted up, It showed 2 displays .. both being powered with the Intel GPU. It took an hour of messing with it, finally I selected Mirroring in the intel screen, and disconnected it.. took a second.. RX580 is finally enabled.

I'm in Catalina now, doing system tasks. I will do a full system back up, then see if Rx 580 survives a reboot.

P.S. I'm really mad because drive icons are all wrong! I had it so pretty ! lol

Sorry about my meandering composition, I'm writing this before my second cup of coffee.

Thanks all!


macrumors regular
Original poster
Jun 11, 2017
San Diego, California

If you restart the Mini with the eGpu only connected ( Just like it worked in Mojave) The Mini boots to a weird color washed out apple, then activates all fans on the eGpu. It then reboots.. over and over..

If you connect the internal intel HDMI port, It boots, you then can select the monitor tab that is connected to the eGpu.. and hope.

If it connects, you can disconnect the internal, and are back to full force , full acceleration.

Let's hope they fix this. In Mojave, I could simply boot into either Windows, or Mac OS and wait for a login screen. It was effortless.

If anything changes Ill report it.

Thank you,



macrumors member
It's boss, same problem here! If the last update of Mojave 10.14.6 does not solve this we can only wait for the final version of Catalina. It seems to me that this Beta besides causing problems for eGPU users, is also preventing us from doing internet recovery (error code -9000F). I noticed that I am not allowed to reactivate the Startup Security Utilities protections. After removing Catalina and reinstalling Mojave with a Pendrive I noticed that something in the Bios of the Mac Mini 2018 was changed, because although it is not possible to boot the system with only eGPU, now the screen with the apple logo appears and then the coolers of the Akitio Node eGPU and RX 580 go to 100% and then turn off
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macrumors 68000
Aug 27, 2006
I have both the internal (HDMI) and eGPU (DisplayPort) connected upon boot. I boot it up via HDMI and then switch it (via monitor settings) to eGPU after the blank background comes up. The eGPU has the login screen on it. I leave both plugged in at all time and when I shut down, I switch it back to HDMI for the next boot.

For the applications, most of the main ones I use … browsers, Quicktime/video, mail, etc… have changed in “Get Info” for them to “Prefer External GPU”. Although, this step is probably not necessary.

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