iMac 2020 - Downgrade OS

[blufrog]

Hi,

My father has what I think is a 2020 Intel iMac 4K, and it is currently running Monterey, but it is very very slow.

I have checked to see what is running on it, and deleted a lot of rubbish that started up at boot, but this did little to improve things.

I read that Monterey was the first OS to be "optimized for Apple Silicon" which I assume was the M1. Is this why it is slow?

I can't remember which OS it originally shipped with, but I was thinking of rolling it back a version to 11.x and seeing if it improved things.

Is there a recommended way to do this? I know I should be able to reset it back to the OS it shipped with, but nothing from that era works from an online perspective. A massive problem is the app store no longer works, so nothing can be re-installed from it.

Any help/advice appreciated.

 

[Bigwaff]

Does the iMac have a Fusion Drive? If so, that is most likely the culprit. Fusion Drives prone to failure. Slow performance harbinger of death. Replace with SSD.

 

[Ruggy]

Fusion drive is likely the answer but when you say slow is it slow at everything? Is it slow trying to load web pages, is it slow when you are handling big files or just everything is slow?
If the problem is outdated apps then you could try going to Sequoia but it maybe that the HD is nearly full too so check storage and that will slow things down. Cleaning up start up items can help but you've done that. If you've got Google or some such starting that can slow things down as they have a time out if you block ads.
It's not really that old and we've got 2020 machines here still running fine and one 2016 still zipping along.
There's a lot more to check
Having an SSD is probably the answer though.
If you aren't an Apple person the Apple logo top left will lead you to checking on system settings, resources, storage etc and it may well be worth running hardware diagnostics to see if the drive is failing (you do that from start up but it changes with the OS I think so you'll have to look that up).
You may have malware too so you could try Malwarebytes free version to check for that

 

[curnalpanic]

Yeah, use an SSD and maybe a fresh install of the latest supported that is not Tahoe.

 

[Fishrrman]

I tried searching everymac.com for a 2020 4k iMac, and came up with ... nothing.
2019 4k iMac, yes, but 2020? No.

These look like they came with "fusion" drives. A fusion drive is actually TWO drives "melded" into one volume:
- small SSD (about 32gb)
- larger HDD (1tb)
They worked ok when new, but can get "clogged up" as they get older.

The advice given above about moving to an SSD is good...
BUT
... you almost certainly DO NOT want to try to open the old iMac, as the job isn't going to be easy. Quite difficult on these, I understand.

There's "a better way" to speed things up.
That is:
1. get an EXTERNAL SSD, 1tb in size (or larger if you want). It should be "USB3.1 gen2", and should yield 10gb speeds (older, plain-vanilla "USB3" drives are generally 5gb).
2. Connect it to the iMac USBc port (don't use USBa) and format it to APFS, GUID partition format
3. At this point, you need to decide to either:
3a. Start with a fresh OS install, or
3b. "Clone over" the contents of the internal drive to the new SSD.
Cloning is the "fast n easy" way to go, and it just may work and solve your problems. I'd suggest you try that first.
Here's how to proceed:
a. Download the app "SuperDuper" by clicking this link:

https://shirt-pocket.com/mint/pepper/orderedlist/downloads/download.php?file=https%3A//shirt-pocket.com/downloads/SuperDuper%21.dmg

SuperDuper is one of the easiest-to-use apps out there. No instructions needed, really. You'll see what to do. It's also FREE to use for what we're going to do.
b. Use SD to clone the contents of the iMac internal drive to the SSD.
c. When the cloned backup is done, open the Startup Disk settings pane
d. Do you now see the external SSD there, as well as the internal drive? Then you know the clone "is good".
e. Set the SSD to be the boot drive (password required).
f. Reboot
g. You should now boot from the SSD. If it's "a good boot", have your father log in and "look around".
Do things look ok?
That's really all there is to it.
You can just "leave the internal fusion drive as it is". It won't hurt anything.

By the way...
everymac.com shows the factory-installed OS for a 2019 4k iMac to be 10.14.4 "Mojave".

I still use Mojave on my 2018 Mini -- it's an excellent OS version, and the last that can run older 32 bit apps.

But once you're booting and running from an SSD (even external), things will probably go considerably faster, even with the Monterey OS.

The alternative...
Since the iMac is now 7 years old, you might start thinking about a replacement in the future.
I'd suggest (rather than iMac), a Mac Mini.
But be aware that supply on the m4 Minis is VERY constrained right now.
Better to wait for the m5 Mini that's probably coming in the fall...