Been messing with this for a week or so and have found a reliable way to boot using an Nvidia card on a 13" MacBook Pro Retina from early 2015, which is known for having a lot of issues.
- Shut down MacBook & eGPU
- Boot into Windows 10 & do not connect/power on eGPU
- Shortly after boot completes, click Start, then Restart
- Right after clicking restart, power on eGPU quickly but do not connect the Thunderbolt cable yet
- Make sure to hold Option again whilst your MacBook reboots
- On the boot menu, wait until the WiFi loading spinner stops, then boot into Windows
- Connect Thunderbolt cable as soon as blue Windows logo appears, but before the loading spinner starts
These steps work 100% for me now.
TL;DR, shut down fully, boot into Windows, click Restart, power on eGPU, then connect Thunderbolt right at the Windows logo after reboot.
Hope this helps!
Thank you for posting your findings with the Early 2015 13" MBP. Would you like to post some pictures of your setup and benchmarks?
Mate you are a legend.
Couldn't for the life of me get this to work until i tried your trick. Still can't get OSX to use the epgu, but my windows 10 bootcamp install now works like a treat.
It takes longer than usual to get to the desktop, but works for me, too. I haven't tried that whole USB drive workaround yet, but for the amount I need to boot this laptop with the eGPU I'm glad I don't have to worry about it for now.
I specifically set up an account just to tell you that your instructions were hugely helpful to me. My first attempt failed spectacularly, but once I reset everything and tried your instructions I am now successfully booted into Windows 10 and running my eGPU off the internal laptop panel. Thank you very much. Using Windows 1803, so outside of Nvidia drivers for my 1050 TI I didn't have to install anything else. No error 12.