Downgrading MacBook Pro to High Sierra (APFS)

[flightmedic]

So, I just bought a Mid-2012 (Non-Retina) MBP that has Catalina on it.

I would like to downgrade the MACOS to High Sierra. I have a bootable USB but I cannot load the OS because the SSD is already formatted to APFS.

Is there a workaround for this? When I try to reformat, APFS is the only option.

Would like to reformat to HFE+ or be able to load the OS onto APFS.

Any ideas?

Thanks in advance.

 

[DeltaMac]

When you have the Disk Utility open (also assuming that you are either booted to recovery, or an external bootable installer), click on the "View" menu, and choose "Show All Devices". You can then click on the SSD, which will usually be the top item in the list, and should have the drive's manufacturer's info. Select THAT line, then you will find that "Erase" will give you the choice for Mac OS Extended (journaled). The High Sierra install will convert the drive to APFS automatically, as part of the install, same as all later macOS versions will do. The problem that you have right now, is that the Catalina install version of APFS is a newer APFS version, and the older High Sierra install doesn't recognize that as a "proper" format. Follow my steps above to erase the internal SSD completely, and that will then allow the High Sierra install to continue.

 

[Fishrrman]

OP:

DeltaMac has the answer. I'll outline it, as well.

You must:
a. boot from the USB flashdrive installer
b. open disk utility
c. GO TO THE VIEW MENU AND CHOOSE "SHOW ALL DEVICES" (shouting is intentional)
d. Look at the "list on the left" -- the topmost item should be the internal drive
e. Click on the internal drive to select it, then...
f. ...click "erase" so that you will erase THE ENTIRE DRIVE
g. HFS+ should be available (it's "Mac OS extended, journaling enabled, GUID partition format").
h. erase the drive, quit disk utility, open the OS installer and try again.

 

[freebrian]

OP:

DeltaMac has the answer. I'll outline it, as well.

You must:
a. boot from the USB flashdrive installer
b. open disk utility
c. GO TO THE VIEW MENU AND CHOOSE "SHOW ALL DEVICES" (shouting is intentional)
d. Look at the "list on the left" -- the topmost item should be the internal drive
e. Click on the internal drive to select it, then...
f. ...click "erase" so that you will erase THE ENTIRE DRIVE
g. HFS+ should be available (it's "Mac OS extended, journaling enabled, GUID partition format").
h. erase the drive, quit disk utility, open the OS installer and try again.

I was worried after upgrading to Catalina on a Mac Mini 2012 that if I downgrade to High Sierra I would not be able to reformat the internal disk to HFS+, because the combination of Catalina /APFS really really slowed down my system when it was working alright days ago. Made the drive feel its age. I hope that following these steps will restore it to the way it was.

So the High Sierra installer will not automatically convert the internal hard drive back to HFS+ and I have to do that manually BEFORE running the installer. That is really important to know.

 

[MacsolverUK]

The 13" Mid 2012 MacBook Pro has user upgradable memory and drives. Has yours got an SSD and 16Gb of Memory yet ? It is possible to fit a second SSD in the optical bay too. "How to" here:

MacBook Pro 13" Unibody Mid 2012 Repair Help: Learn How to Fix It Yourself.

Mid 2012 model, A1278 / 2.5 GHz i5 or 2.9 GHz i7 processor.

www.ifixit.com

Monterey runs fine on these MacBooks with an SSD and 16Gb memory. Install info here:

Supported Models | OpenCore Legacy Patcher