Mine is a 2009 with upgraded firmware to MacPro5,1 MP51.0084.B00, processor upgraded to 6-core Xeon 3,46GHz and MSI Radeon RX 480. I removed the original GeForce GT 120 because the installer indicated that all graphics card need to be Metal enabled, even if my display is connected to the Radeon. Then relauched the installer only to see that my computer needed a firmware upgrade. I went through the upgrade twice now, not seeing the gray screen because it's a graphics PC card, but it reboots normally but nothing has chaged. I'm trying to intall on an external drive connected through FireWire.
Thanks for the reply. I'm hesitant to mess around too much with a firmware update that is balking.
Finally, successfully installed Mojave Beta. It took me a while because I had an issue with my DisplayPort cable, which I had to replace. Here is what I did wrong in my first attempts:
- download macOSBetaUtility and the macOS installer to external drive (the install destination)
- try to run the installer from internal boot volume which had FileVault enabled
How I fixed the issue:
- disabled FileVault on my internal volume
- re-launched the intaller from the destination drive
- after the system had shut down for the firmware update, I first reinstalled my nVidia GeForce GT 120 and connected my display to it.
- I then held the power button to initiate the firmware update, and this time with the GT 120, I could see the progress bar.
- when the system rebooted I could confirmed the firmware is now MP51.0089.B00
- shut down the system and remove the GT 120 graphics card
- reboot with only Metal supported graphics card and re-lauch the macOS beta installer
That's it. Apparently my mistake was thinking that FileVault had to be disabled on the destination drive only. Since I was trying to run the installer when booted from another drive it failed. I've only used Mojave for a few hours now, so I can't really comment on it. But at least it is installed and I can boot into it when I choose to.
Thanks for being the guinea pig and reporting your success.