iMac 12,1 21.5" Mid 2011 Issues Updating OS
Trying to make this computer useful for a friend...It has a hard drive that cannot be erased but is still recognized as a device. Attempting to install High Sierra on an external drive and operate the computer from that.
Cannot install any Boot Rom updaters such as: Mac EFI Security Update 2015-001
Boot Roms are version 52 and should be version 55
It cannot boot from a USB drive or install any system on a USB drive
It does boot from Firewire 800 drive with El Capitan and Sierra. I have installed both systems using this computer but he rom version never updates.
It will NOT install High Sierra saying that a Firmware Partition is missing.
Any input on how to get the boot roms to update and get it to boot from USB along with that High Sierra install issue would be appreciated. At this point attempting to install High Sierra on the Firewire 800 drive unless I can get USB boot to work.
iMac 21.5", macOS 10.12