New September 2017 iMacs - downgrade to Sierra?

Question

New September 2017 iMacs - downgrade to Sierra?

There are many reasons why one would want to downgrade the OS on a computer. At the top of the list is compatibility with existing mission-critical software.

Apple says the current iMacs purchased from Apple's online store (that ship with High Sierra preinstalled) cannot be downgraded to macOS Sierra.

Does anyone know whether this is correct or not?

Previously, one could purchase iMacs preinstalled with Sierra and downgrade to El Capitan.

This was because the hardware revision at the time was released while El Capitan was the "current" OS.

The same is true of the current (as of 4 October 2017) iMacs i.e. when they were released, Sierra was the "current" OS.

Would appreciate any information!

Cheers

Robin

iMac, macOS High Sierra (10.13)

Posted on Oct 3, 2017 10:30 PM

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Answer 1

Top-ranking reply

EdgarRothermich

Level 5

5,004 points

Jan 7, 2018 11:38 PM in response to robinfromauckland

Good news, it finally works (without major Terminal surgery).

I made a simple pilot error when trying to reformat the built-in SSD drive of the new iMac, I selected the volume instead of the drive. When selecting the drive, it let me format it to HFS+.

Then I booted into the external drive that had the original High Sierra system on (I cloned to ) and restored the Sierra Drive (that I cloned from my old iMac) onto the internal SD drive of the new iMac using Carbon Copy Cloner5 ( tried the restore with CC4 from a Sierra system but didn't work, I don't know why).

BTW, I tackled to Apple customer and they confirmed: You can't install Sierra on an APFS formatted drive. iMac Pro can only have High Sierra (and higher). The current iMacs can have Sierra and El Capitan.

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Answer 2

babowa

Level 9

78,568 points

Dec 5, 2017 8:29 AM in response to robinfromauckland

There is no generalization possible. If a Mac was made before High Sierra was introduced, it can be booted with Sierra (and that would include current/available stock at resellers - machines that were made before HS). If it was made after High Sierra was introduced and was originally loaded with High Sierra, it cannot boot from an earlier OS.

https://support.apple.com/en-us/HT201686

https://support.apple.com/en-us/HT201260

And, according to the ultimate list here, all mid 2017 iMacs were originally loaded with a version of Sierra:

https://everymac.com/systems/by_capability/minimum-macos-supported.html

Since there hasn't been a newer model introduced, they should be able to boot from Sierra although they are now loaded with HS and a downgrade is not supported by Apple as they are "current-OS-centric". As I said, it totally depends on the build number of the Mac.

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Answer 3

Dec 5, 2017 10:24 AM in response to babowa

Hi and thanks for the engagement. Hopefully somebody will read this and find the discussion useful.

I'm a fan of keeping things simple. iMac hardware models (not minor upgrades of components such as graphics cards and the like) will run an OS that is current at point of release, or any OS subsequent (not forever obviously, but for quite a few years).

Example: current iMacs will run both High Sierra (shipped OS) and Sierra (current at time of hardware model introduction). I researched this and can now confirm it is correct. The iMac with High Sierra in a box five metres from me now will soon have Sierra installed and run perfectly.

Generally I consider Apple's information to be guidance rather than fact, per se.

Regards

Robin

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Answer 4

Jan 28, 2018 6:20 PM in response to yannivelez

Hi Yanni

Yes you can downgrade this machine. I have done so with quite a few of precisely this model.

If you have an SSD then pay attention to correctly formatting it in HFS+, and to deactivating and then reactivating TRIM to address extremely slow startup issues if you encounter this issue.

Regards

Robin

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Answer 5

babowa

Level 9

78,568 points

Oct 3, 2017 10:51 PM in response to robinfromauckland

Macs can only boot from the OS version they came with originally. That has always been the case. If you order a new model which was originally rolled out in 2016, then you may be able to install/boot from an OS version which was used at that time even though the later build wound up having a newer OS installed. Here is a list of build numbers:

Find the macOS version number on your Mac - Apple Support

Use the Mac operating system that came with your Mac, or a compatible newer version - Apple Support

If you want a Mac that can boot from an earlier OS, you will need to check when which OS version was installed originally and then find the particular model - I always buy mine at the refurbished section of the Apple online store (and I carefully choose which model I want).

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Answer 6

babowa

Level 9

78,568 points

Oct 4, 2017 8:25 AM in response to robinfromauckland

You did not understand my reply (and it was correct). It depends on which OS that model was introduced with originally, not necessarily what was pre-installed.

I bought a refurbished 2012 MBP this year from Apple. It came pre-installed with Sierra. I had them wipe that when I picked it up at the store and install the original OS (10.7.3). This was possible only because the model originally came with 10.7.x.

On the contrary, if your 2017 Mac originally had Sierra (never mind what is installed when you actually buy it), you cannot install anything older than that.

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Answer 7

JimmyCMPIT

Level 7

29,306 points

Oct 4, 2017 11:12 AM in response to robinfromauckland

the last generation of iMacs (mid 2017) will allow you to install OS X 10.12.4 Sierra (or 10.12.5, or 12.12.6) even if they ship with 10.13 High Sierra - this means if you have an archived installer for Sierra 10.12.3 you will NOT be able to install it on that system (the "current" last of the mid 2017's)

To install Sierra from the App Store you need to have it in your Apple Store account ID or you can no longer legally obtain it from Apple.

If you do have it you will only be able to download 10.12.6; but you may be able to get Sierra through Internet recovery. I'm not entirely sure Apple does this with every system they release but I have found they have done it with some: About macOS Recovery - Apple Support

You may also need to download (from the APP Store, not Recovery) on a Mac running something less than 10.12.6 even if you own Sierra. Historically if Apple were to release any new configuration of a computer today or sometime during or after a 10.13 updae it would come with whatever is the current OS 10.13.x was when they ship and nothing less than that.

As of right now I can't verify the "may" because on my own account it's showing I have the Public Beta but not the release. However I DO have a 10.12.2 installer on my computer I kept archived because I just used it last night for a re-image and I only have one account - and at least several iMacs in my name that shipped so no idea what's going on.

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Answer 8

dwb

Level 7

33,262 points

Oct 4, 2017 9:44 AM in response to robinfromauckland

Read babowa's second comment. If you purchase a computer that is shipping right now, while it may come with High Sierra pre-installed, when Apple originally introduced it, Sierra was still shipping. You'll have to supply your own Sierra installer or have a complete TimeMachine backup or clone with Sierra. If you do you should be good to go. On two occasions since OS X 10.4 I've been in the same boat you are: the computers with the new OS were shipping but I needed to continue using the older OS for a while longer. I used a cloned external drive from my old computer to assure myself everything was okay and then moved the older OS to the internal drive using TimeMachine restore.

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Answer 9

Dec 8, 2017 12:52 PM in response to babowa

If it [an iMac] was made after High Sierra was introduced and was originally loaded with High Sierra, it cannot boot from an earlier OS.

Incorrect. I know because I have personally verified this. 100% confidence.

→ Macs made after High Sierra was introduced and originally loaded with High Sierra can boot Sierra.

The only qualifier is that this will no longer be true at the point where Apple makes the next iMac hardware revision for this model. Then, iMacs of that revision will be unable to boot Sierra (or earlier OSs).

Can we draw a line under this discussion please? My original question asked whether this was possible with the current iMacs (again as of 3 October 2017, and by the way still correct as of 9 December 2017) and the answer I have now confirmed is YES.

Thanks to all.

Robin

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Answer 10

Dec 4, 2017 10:49 PM in response to robinfromauckland

Just a quick followup to say that this worked fine. Current (as of December 5, 2017) imacs can, contrary to official Apple advice, be downgraded to macOS Sierra 10.12.x

Thanks for all who answered my original question!

Robin

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Answer 11

Nov 8, 2017 1:20 PM in response to robinfromauckland

Hi Robin,

I'm an Apple Consultant in Los Angeles. I thought I would share for anyone that needs it, you can still download the full 10.12.6 version installer for Sierra from the AppStore (at least one can do so in in the U.S.--not sure about NZ), but you can't find it by searching within the AppStore itself. Frustrating if you've been searching for it, but I'm betting Apple did that to prevent any confusion for anyone searching within the AppStore for the most recent OS release. The following link can be used to download it, this will open up a hidden link within the AppStore for macOS Sierra, after which you can download it. Hope this helps a few people! https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12

Best,

Mike

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Answer 12

Dec 21, 2017 9:58 AM in response to mesrouilles

Do you have another mac you can install Sierra on, make an image of, and then restore the image to your new iMac? To do this would will need to boot from an external USB drive and have the image on the same drive. If you use Carbon Copy Cloner you can also recreate the recovery partition on the destination if your external boot has the recovery partition.

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Answer 13

Jan 3, 2018 11:35 PM in response to EdgarRothermich

Hi Edgar

Not the end of the line.

Check this out:

https://www.techrepublic.com/article/how-to-revert-back-to-apples-hfs-from-apfs/

Boot to external drive, and head off to Disk Utility. With care, follow above instructions to revert to HFS+

When booting to your SSD in Sierra, if you experience a startup delay before you see the Apple logo, check System Profiler under PCiE or SATA to see if TRIM is supported by your SSD.

If it is, use trimforce to disable and reenable TRIM. If not, do the reverse

Fire up Terminal and use:

sudo trimforce enable

or

sudo trimforce disable

More background:

Installing an SSD on your Mac? Don't make this mistake - CNET

Any issues just come back here and ask.

Cheers

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Answer 14

Oct 4, 2017 12:38 AM in response to babowa

Hi Babowa

Thanks for your reply.

Macs can only boot from the OS version they came with originally.

That's precisely the point - this is not correct.

I have personally installed OSX 10.11.x on Macs that came with Sierra pre-installed.

Regards

Robin

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Answer 15

JimmyCMPIT

Level 7

29,306 points

Oct 4, 2017 9:47 AM in response to robinfromauckland

to add to all that has been said about the OS that shipped with that model at the time of it's release if it's not the OS that shipped on the model you bought Apple DOES NOT void any warranty if you downgrade. I had to do this to a half dozen systems and a sr. Advisor at Apple explained to me the warranty and Apple Care would remain intact.

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