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Old 09-12-2019, 04:56 AM
musicman691 musicman691 is offline
Join Date: Dec 2009
Location: The Soprano State (NJ)
Posts: 16,663
Default Re: Slate urges against early odoption of new MacOS.

Originally Posted by Sardi View Post
But itís a firmware update for the hardware in his Mac, so regardless of the individual drives and partitions, it will globally affect his system.

However, I have never heard of a FW update preventing backwards compatibility and booting of an older OS. I have High Sierra on one of my laptops and recently cloned back an old Mountain Lion partition to the same drive without any issue. Iíve done the same sort of thing countless times in the past on MacBooks, iMacs and Mac Minis - never an issue.

However, if this is relating to an older MacPro with a patched system allowing it to run newer versions of Mac OS, then I donít know. Technically, youíre using an unsupported configuration and thus if a newer EFI update did something to your system, itís not really on Apple to fix it. IOW - itís up to the user and the help of the internet to get that machine up and running again.

I sense thatís probably the hesitation.

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Mine is a 5,1 2012 cheesegrater. So it's not a patched system.
Where I get conflicting info is in regards to ssd's. As we all know HS changes an ssd to APFS which is all well and okay. What I can't find concrete info on is with a dual boot system as my system ssd is split into OSX 10.10.5 and OSX 10.12.6. Most web pages I've found only deal with a single partition.

Before you cloned back the ML partition how was your system drive formatted - APFS or HFS? I'm under the impression that anything older than Sierra won't run on APFS. I've only ever cloned back and forth within HFS. I run Carbon Copy Cloner.

I know this is taking the thread a little OT but I want to get my ducks in a row before PT 2020 hits. If it ever does
See profile for system details
iMac dead & retired as of 11/4/17

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