Partition Mojave HD to run Sierra

Started 5 months ago | Discussions thread
silentstorm Senior Member • Posts: 1,486
Re: 2 things come to my head

ChrisLumix wrote:

"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.


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.

That's only partly true. My original 2011 iMac shipped with Lion. The supplier was able to erase and reformat the HD and install Snow Leopard on it. That model (not that machine) originally came with Snow Leopard, though later sales were shipped with Lion.

So the "shipping" point is not as moot as which particular OS the model in question FIRST SHIPPED WITH. Later examples may ship with a later OS but that doesn't mean the original OS for that model can't be installed.

No. It is very true. What you and Albert experienced is timeline down the road OS updated, and considered going back to original OS as older OS. Your supplier updated older machine to Lion and sold it to you. You as the customer perceived it as default OS from the shipped machine, but in actual fact it was updated w/o your knowledge.

My Air was bought on 1 week Aug 2011, and was shipped with Lion (end July 2011 released). I cannot get it back to SL. The firmware blocked everything.

For OP case, if his Air came with Sierra, or similar to your case the Air was updated to Hi Sierra from an older machine before shipped, he can go back to original shipped OS. If his Air was bought later in Nov 2017, he can't go back any older than Hi Sierra. For us to know what is what, OP need to test it out himself to see if a wiped drive can install Sierra.  All we can do here is speculate over his situation.  Hopefully he would update us on his progress.

Coming back to the timeline, if anyone were to buy a new apple computer today shipped with Big Sur, what would you consider as older OS?  Big Sur? Since Monterey was already announced?

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