I have used CCCloner to transfer the OS & programs to a Firewire external THEN when so desired started from the external - no problems.
I just cloned Sierra from one machine to a USB3 external.
Then I tried to start from the external connected to a machine w/ Mavericks - there was a circle w/ a slash through it.
Tried again this time erasing the external with DU before cloning - same problem.
Perhaps the Sierra clone can only start a machine with Sierra - if the external is USB (rather than Firewire)?
I just cloned Sierra from one machine to a USB3 external.
Then I tried to start from the external connected to a machine w/ Mavericks - there was a circle w/ a slash through it.
Tried again this time erasing the external with DU before cloning - same problem.
Perhaps the Sierra clone can only start a machine with Sierra - if the external is USB (rather than Firewire)?