High Sierra on 2019+ intel iMacs

mike18xx · Jan 27, 2023

Device: iMac19,2 (a 21.5" 4K 3.6ghz i3 with 8gb ram and a 1TB rotational drive).
Situation: I already have a 'master' High Sierra installation on an external SSD.
Problem: While I don't get the "No!" slashed-zero, booting hangs at third-of-the-way.
Goal: Patch High Sierra (add kexts, or whatever) to launch 2019+ intel Macs.
Important consideration: OS must launch from HFS+ partition on a rotational drive.

Annoyance: Mojave (oldest OS supported on 2019+ hardware) can run from an HFS+ partition (via Carbon Copy Cloning from its installed APFS container into a prepared HFS+ partition), and does run on the 2019s, but is noticeably slower with higher memory consumption than High Sierra (using up an extra 1gb to 2gb at-rest on a fixed-8gb machine). This results in a 2019 machine with inferior performance compared to a similar 2012 21.5" with a slower processor running High Sierra. Needless to say, upgrading to any Catalina or newer OS (e.g., System Preferences pesters me to upgrade to Ventura) will result in an APFS-formatted rotational drive being thrashed to pieces (so we're not going to do that; additionally, 32bit support ends with Catalina, meaning no CS6 for quick-n-dirty photo edits, and no Peggle or Angry Birds for the kids).

There are lots of guides on how to install newer OSes on older unsupported machines, but a dearth of those patching older unsupported OSes to run on newer machines. Help me out. TIA. (The ideal solution would be a DosDude-style post-installation patcher.)

wstrohm · Feb 4, 2023

Not on point at all, since you are referring to an actual Mac, not a Hackintosh, but...
My "Mini-ITX 3" Hackintosh listed below is configured with HFS+ on High Sierra 13.6, and is booted with an OpenCore EFI boot loader in its EFI partition. Its SMBIOS is iMac18,3 rather than iMac 19,2. You have not filled in information in your Signature regarding graphics or CPU (it's an i3, but i3-8100?), but if it's a Mac, that should be what it is.

Does your "Problem" above occur when attempting to boot your Mac from your "master" High Sierra installation SSD? If so, what is in the EFI partition on your SSD? Clover or Open Core? Version?

Why do you reference a spinning hard drive when this web page specifies a 256 GB SSD is the storage device in your Mac?

wstrohm · Feb 4, 2023

Agreed. Where should it be?

trs96 · Feb 4, 2023

wstrohm said:
Agreed. Where should it be?

Moved to iMac forum. Done.

mike18xx · Feb 4, 2023

wstrohm said:
Not on point at all, since you are referring to an actual Mac, not a Hackintosh, but...
My "Mini-ITX 3" Hackintosh listed below is configured with HFS+ on High Sierra 13.6, and is booted with an OpenCore EFI boot loader in its EFI partition. Its SMBIOS is iMac18,3 rather than iMac 19,2. You have not filled in information in your Signature regarding graphics or CPU (it's an i3, but i3-8100?), but if it's a Mac, that should be what it is.

Does your "Problem" above occur when attempting to boot your Mac from your "master" High Sierra installation SSD? If so, what is in the EFI partition on your SSD? Clover or Open Core? Version?

This particular High Sierra installation of mine doesn't use an EFI partition; it's a vanilla HFS+ partition tweaked with a DosDude post-install patcher. Presently, it'll boot any iMac from a 2008 Core2Duo to 2017 or 18. AFAIK, OpenCore doesn't offer a patch kit to let older operating systems run on new hardware, and I've never used Clover. (And I'd like to avoid EFI schemes, if possible.)

Why do you reference a spinning hard drive when this web page specifies a 256 GB SSD is the storage device in your Mac?

Because the site is wrong or incomplete. Apple routinely sells several ram/hd/processor variants all using the same "iMacX,Y" model number scheme. This particular machine is probably either the base model for the year, or originally sold only to institutions (i.e., schools) that just needed something to be turned on all day running propriety software. This 2019 21.5" has 8gb ram and a 500gb rotational drive.
[/QUOTE]

wstrohm · Feb 4, 2023

I watched "dosDude's" video.You might want to contact him in case he has more recently written a patch for your iMac19,2. Other than that, if you want to avoid using the EFI partition I have no ideas. OpenCore works fine on my Coffeelake motherboard with my i7-8700 CPU, but on a real Mac? Have no idea, sorry.

mike18xx · Feb 5, 2023

wstrohm said:
I watched "dosDude's" video.You might want to contact him in case he has more recently written a patch for your iMac19,2. Other than that, if you want to avoid using the EFI partition I have no ideas. OpenCore works fine on my Coffeelake motherboard with my i7-8700 CPU, but on a real Mac? Have no idea, sorry.

I can try to reach him (didn't know he was still active), but I get the general impression that no one's ever thought to run an older OS on newer verboten architecture. The major annoyance with EFI schemes (OpenCore, et al) is that they do not permit easy one-stage backing up via Carbon Copy Cloner and similar within-the-OS tools.

(Side note: To get some idea of how fast Apple is pushing artificial obsolescence of its own hardware and software now, note that High Sierra debuted on September 25, 2017 and its last Security Update was in 2020. This means these 2019 machines were launching with a Mojave minimum requirement while High Sierra was still a temporally-"current" supported OS. And some of those Mojave-requirring 2019s were bog-slow pieces of junk compared to half-decade-earlier 2012-14 flash-SSD/Fusion rocketsleds. There's no reason on earth that High Sierra shouldn't be able to run on intel 2019s aside from Apple withholding a few kexts to cause that OS to hang. All the big techs were colluding at the time to flush away the vast libraries of free and abandonware 32bit software, and herd everyone into their yearly-subscription-model AppStore-only future. /rant.... )

wstrohm · Feb 11, 2023

I apologize for my late response to this thread. Tonymacx86 has apparently blocked my ISP (Spectrum/socal.rr.com) and I had to download and install Cloudfire WARP to get back in today.

From re-reading this thread, I am taking a leap to write that I think you might be better off upgrading your High Sierra install to Mojave 10.14.6, and here is why:

1. It is the latest Mac OS which will still run both 32-bit and 64-bit applications. That ceased with Catalina.
2. It runs fine using Apple's Extended HFS Journaled file system, if you go through the effort which you did for High Sierra.
3. It uses the "new" App Store client and can access Apple's latest App Store server.
4. It may not make a difference for you, but it also includes an optional "Dark Mode" (if you like that sort of thing), and a dynamic Desktop (changes with time of day).
5. It can still use the same version of Carbon Copy Cloner as High Sierra (CCC version 5.1.28).

I use this particular Mac OS version on my computer at left (SMBIOS iMac19,1), and prefer it to all others I have experienced.

Your iMac19,2 should accommodate 10.14.6 with no problems. Of course if you do this, you will need a Full Installer of Mac OS 10.4.6. It is 6.05 GBytes in size, and can only be directly accessed from a MacOS running High Sierra. Later Apple servers only connect to a "stub' of about 41 Mbyte size, which needs a lot of (IMHO) effort and time to finally get to a working Mojave. In case you want to try this, I have attached a link in the TextEdit file below to the full installer. If the link takes you to an Apple website with a Download button, as in the image in the attachment, you will get the full installer.

Of course if you download and install Mojave, you will have an AFBP file system on your target disk, and you will have to go through the same routine you did to get High Sierra running HFS+ on your external SSD. Again IMHO it is well worth the trouble. Your hard disk is much more compatible with HFS+ than with APFS, and apparently your iMac wants Mojave anyway.

Good luck!

mike18xx · Feb 11, 2023

wstrohm said:
I apologize for my late response to this thread. Tonymacx86 has apparently blocked my ISP (Spectrum/socal.rr.com) and I had to download and install Cloudfire WARP to get back in today.

From re-reading this thread, I am taking a leap to write that I think you might be better off upgrading your High Sierra install to Mojave 10.14.6, and here is why:

1. It is the latest Mac OS which will still run both 32-bit and 64-bit applications. That ceased with Catalina.
2. It runs fine using Apple's Extended HFS Journaled file system, if you go through the effort which you did for High Sierra.
3. It uses the "new" App Store client and can access Apple's latest App Store server.
4. It may not make a difference for you, but it also includes an optional "Dark Mode" (if you like that sort of thing), and a dynamic Desktop (changes with time of day).
5. It can still use the same version of Carbon Copy Cloner as High Sierra (CCC version 5.1.28).

I use this particular Mac OS version on my computer at left (SMBIOS iMac19,1), and prefer it to all others I have experienced.

Your iMac19,2 should accommodate 10.14.6 with no problems. Of course if you do this, you will need a Full Installer of Mac OS 10.4.6. It is 6.05 GBytes in size, and can only be directly accessed from a MacOS running High Sierra. Later Apple servers only connect to a "stub' of about 41 Mbyte size, which needs a lot of (IMHO) effort and time to finally get to a working Mojave. In case you want to try this, I have attached a link in the TextEdit file below to the full installer. If the link takes you to an Apple website with a Download button, as in the image in the attachment, you will get the full installer.

Of course if you download and install Mojave, you will have an AFBP file system on your target disk, and you will have to go through the same routine you did to get High Sierra running HFS+ on your external SSD. Again IMHO it is well worth the trouble. Your hard disk is much more compatible with HFS+ than with APFS, and apparently your iMac wants Mojave anyway.

Good luck!

I've had a couple goes with Mojave; each time it seems OK, but then irresolvable irritants set in.

Point-by-point:

1. 32bit support is there, but for some reason it pukes CS6 (of which Photoshop "Extended" is the prize). Also, despite my efforts at turning off various "feature" crud, it still has an at-rest memory usage running .5 to 1.5gb more ram than High Sierra, and it's not-terribly but still perceptively more sluggish. (High Sierra, otoh, was a bug-fix upgrade of Sierra, and ran faster than its predecessor.)

2. During first installation, High Sierra prompts you to convert your drive to APFS, but it isn't forced. Mojave forces the issue, but, as observed, doesn't actually require it, and can so be cloned to HFS+. (Can either of these be workably cloned back into an APFS volume after having taken a stint through HFS+?)

3. That's a demerit-in-a-blessing disguise, because the fastest way to obsolesce (or even accidentally brick) your Mac now is to upgrade the OS to whatever latest you-are-now-an-unpaid-betatester-on-an-OperationCHAOS-treadmill version Apple is foisting (and god help anyone with automatic updates set). The concept of long-term stability seems to have vanished entirely as a desirable aspect. Even with Notifications disabled (via Terminal wizardry), the annoying little bright red "Update me!" dot remains on the System Preferences dock icon.

~ ~ ~

"...you will need a Full Installer...." -- I don't even bother with AppStore/Apple-provided sources anymore, preferring instead to grab a DosDude patch-installer (which includes the latest full installer) to make a bootable HFS+ partition...which I can then easily clone/shrink to a backup volume, or create a compressed dmg archive of with Disk Utility.

wstrohm · Feb 11, 2023

mike18xx said:
I've had a couple goes with Mojave; each time it seems OK, but then irresolvable irritants set in.

mike18xx said:
it still has an at-rest memory usage running .5 to 1.5gb more ram than High Sierra

I checked Activity Monitor for "idling" Memory usage on my Hack at left running Mojave 10.14.6; summary is shown below. Have not compared it with High Sierra on my backup computer ("Mini-ITX 3" below). I'll do that llater.

mike18xx said:
(Can either of these be workably cloned back into an APFS volume after having taken a stint through HFS+?)

My guess is that you would use the same method in reverse as you used before to get from APFS to HFS+. But have never tried it.

mike18xx said:
I don't even bother with AppStore/Apple-provided sources anymore, preferring instead to grab a DosDude patch-installer

No experience here with DosDude stuff, but the Apple full installer from the link I uploaded does the job and will provide a legitimate version of 10.14.6. Do what's right for you! And Good Luck!

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