Tsialex, you are the man, I got it to work. The cmp can boot and install Mojave with GTX 690, 1080ti has zero support, it can't boot nor install. As far as I know there is no web driver available for the 1080ti, I saw some people running a 1080ti on Mojave, do you have any idea? is it because I skipped the firmware update of mp51.0089.b00?
BootROM has nothing to do with driver support.
Any GPU from NVIDIA newer than Kepler has zero driver support with Mojave until NVIDIA releases the web drivers.
If someone got a 1080 showing screens with Mojave, it's a Mac EFI flashed GPU and is running the un-accelerated default EFI drivers, so it's unuseful to work as is so sluggish to do anything besides showing the screen.
I currently had Mojave installed on an ahci ssd. Base on your other post, you mentioned 138.0.0.0 does not support native boot from NVME, but 140.0.0.0 does. Should I stick with the ahci ssd for now? or is there a way booting from it?
140.0.0.0.0 has support for PCIe booting from NVMe and AHCI, your AHCI PCIe blade will continue to work as always worked before, no changes. We expect that Apple will release 140.0.0.0.0 with 10.14.1 in the next week or so.
My other CMP has the default 5,1 rom that I flashed from 4,1. I download the latest high Sierra and install, it asks me to upgrade the firmware. I enter the password and try to shut it down to continue the process, but the cmp doesn't shut down at all. I am having issue flashing to the latest rom for high Sierra. Should I flash this CMP directly to 138.0.0.0 just like the one I did.
Thank you!
Don't do the flash from the USB installer, do from macOS. Use a Mac EFI GPU to flash until MP51.0089.B00.
If you are having problems with macOS flashing, probably you are using some non standard macOS install and the installer can't bless your drive. Get a empty drive, install it onto the SATA bay, install 10.13.6 into it, update the firmware to MP51.0089.B00 then to 138.0.0.0.0.