Hey KGP, you help me, I help you
We seem to have the same problem. NV card that doesn't allow the installer to boot @ gIOScreenLockState 3
I need Sierra running badly, but with High Sierra
installed and NVIDIA you do this, and it may just work for Sierra:
nv_disable / WebOS checked
Install Web Drivers with SIP enabled; don't reboot
REMOVE NVDAStartup.kext = you can reboot to GUI with SIP disabled (if needed)
nv_disable unchecked / WebOS checked
So I got your High Sierra build running well, but I'd strongly prefer Sierra. Taking the same EFI I use for 10.13 I can't even get past memory allocation when trying the installer, and it goes to black screen on the 10.12.6 SSD I have.
My post @ page 14
My 10.13 EFI (the attachment @ page 14 is 10.12 EFI I previously tried), iMac17,1 edited out.
I'd really appreciate a working 10.12.6 EFI, either ATI/NV don't care. I can't seem to work with the one you supplied in the post, but I'm going at it again.
If you want to chat directly via Skype or something, let me know per DM.
EDIT:
Running your EFI with Test-2016.efi and older OsxAptioFixDrv-64.efi (which together work for my X99 builds) I can get to gIOSCreenLockState 3 when running the installer. The SATA disk still doesn't go, and jumps to black screen before anything when selected; doesn't matter what SATA-port it's on.
I'm very confused about the SATA drive not going, as I always use it as copy drive for 10.12.6 systems, for example copying to NVME drives and just skipping the need of the installer USB.
EDIT2:
@send2moran I'd be interested in that 10.12.6 bootable Installer EFI folder as well!