Firmware problem when trying to install High Sierra

[wnlewis]

I want to install High Sierra on an internal 1 Tb SSD in my upgraded cMP (Early 2009 Mac Pro 4,1 to 5,1, currently running Mojave and Catalina).

The process starts well, the cMP boots from a bootable USB plugged into one of the original USB ports.

About 2/3 of the way through the process, it fails and say that there is a firmware issue.

This is the message:

macOS could not be installed on your computer. An error occurred while verifying firmware. Quit the installer to restart your computer and try again.

Any thoughts or comments?

 

[casperes1996]

Have you set the date and time back to the release year of High Sierra? - Try and set the computer date to something like March 2018 and try again - Might depend a bit on which version of the installer I would guess, but sometime when the certificate for that installer would still be valid. You can change it back after it's installed

Can't guarantee it'll work but it's often the fix for errors installing older versions

 

[wnlewis]

I had forgotten about that so

Have you set the date and time back to the release year of High Sierra? - Try and set the computer date to something like March 2018 and try again - Might depend a bit on which version of the installer I would guess, but sometime when the certificate for that installer would still be valid. You can change it back after it's installed

Can't guarantee it'll work but it's often the fix for errors installing older versions

I had forgotten about that sort of thing. Thanks for reminding me. I'll try it.