High Sierra 10.13 Firmware Update on macpro5,1 affect ability to rollback to Sierra 10.12?

[5050]

Hi everyone,

Attempting to install High Sierra 10.13 on a macpro5,1. The High Sierra update will be run on a separate "test" System Disk before it's installed on the "official" System Disk. Would like to thoroughly put High Sierra through its paces with my current production applications before making the "official" install.

Will the required firmware update affect my ability to use the older 10.12 "official" System Disk on the macpro5,1?

Thanks in advance,

Jon

 

[crjackson2134]

Will the required firmware update affect my ability to use the older 10.12 "official" System Disk on the macpro5,1?

Thanks in advance,

No, it won’t.

 

[5050]

No, it won’t.

Thanks. What does the firmware update modify? Also, will I require an EFI GPU for the update (currently running GTX Titan)?

 

[Macschrauber]

https://forums.macrumors.com/threads/mp5-1-what-you-have-to-do-to-upgrade-to-mojave.2142418/unread

 

[5050]

https://forums.macrumors.com/threads/mp5-1-what-you-have-to-do-to-upgrade-to-mojave.2142418/unread

Thanks for the thread recommendation. Installation of High Sierra on "test" SSD successful. I've rebooted into El Capitan, no problem, but now the High Sierra System Disk does not show (APFS drives not available). Stupid question, but how do I boot from the "test" High Sierra System Disk within El Capitan, as it isn't an option in System Preferences > Startup Disk?

 

[crjackson2134]

If you don’t have boot screens, shutdown the system, pull the ElCappy disk temporarily, and you may need to do a NVRAM reset. This will default you back to the only installed macOS.