I've been running non-EFI GPU's for a while now with a GT-120 also installed for boot screens. All was well until I decided to upgrade my Apple LCD Cinema display (2560 x 1440) to either a 5k or 4k display. First I tried a 5k Dell but had too many issues with it so I replaced it with a 4k Dell. It was during this process that I found many 4k or 5k displays can NOT display boot screens in either macOS or Windows. Even running an Apple EFI card will not produce a boot screen on my 4k display. So...... What to do... What to do..... Well this was my solution. A dedicated 10" 1,920x1,200 display for boot screens, recovery mode, etc... It's plugged directly into the GT-120 and is a bulletproof solution. It works every time!