I have an early-2009 Mac mini with two SSDs, one Mojave and one El Capitan (I still need to run El Cap occasionally because I still use FCP7 for capturing DV via the FireWire port).
Whenever I try booting into El Cap, by restarting and holding down the Option key, there's about a 50% chance the mini will simply shut down a second or two after the chime, as the grey boot screen appears, before I even get the padlock icon to enter my firmware password. The shutdown *only* happens when I Option-boot, it never happens when I let the mini boot automatically into Mojave.
All I can do is press the power button and try again, and eventually it'll boot to the padlock icon and everything proceeds normally from there. Worst-case so far has been four shutdowns in a row.
Anybody know why it's doing this?
Whenever I try booting into El Cap, by restarting and holding down the Option key, there's about a 50% chance the mini will simply shut down a second or two after the chime, as the grey boot screen appears, before I even get the padlock icon to enter my firmware password. The shutdown *only* happens when I Option-boot, it never happens when I let the mini boot automatically into Mojave.
All I can do is press the power button and try again, and eventually it'll boot to the padlock icon and everything proceeds normally from there. Worst-case so far has been four shutdowns in a row.
Anybody know why it's doing this?