Partition Mojave HD to run Sierra

Started 3 months ago | Discussions thread
Tom_N Forum Pro • Posts: 19,170
Re: 2 things come to my head

silentstorm wrote:

JPAlbert wrote:

Again... you CAN install older versions of the OS onto any Mac which was originally capable of RUNNING those versions of the OS.

Oh please Albert. Read my reply again.

For convenience... here is the part again "Especially true if the hardware comes with the newer OS, the firmware in the hardware will block any OSes that are older than the shipped version."

What you said is going back to the original OS that shipped with the hardware. You can't go back older than the shipped version.

If OP MBAir comes with Sierra, then yes, he can reformat his drive and get back the original OS. But if it comes with Mojave, then there's no way he could run Sierra on it, the firmware will block out Sierra.

EDIT:

I just checked, OP MBA laptop is a 2017 model. If it comes installed with Hi Sierra (original shipped OS), then he can't go to Sierra at all.

According to MacTracker, the MacBook Air (13-inch, 2017) originally shipped with macOS 10.12.4, which is a point release of SIerra.

During its retail lifetime (June 2017 to June 2019),  High Sierra came out (September 2017).  Apple would have started pre-installing High Sierra on new MacBook Air (13-inch, 2017) machines, starting then.  However, since the hardware model stayed the same, I don't know if Apple would have actively blocked the installation of Sierra (10.12.4 or later) on a MacBook (13-inch, 2017) that came preloaded with High Sierra and the High Sierra Recovery manager.

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