New 27" iMac - need to downgrade from Catalina

[quatermass]

I just got my shiny new 27" iMac this morning, and it's a fabulous machine from what I can tell so far. Not so fabulous is that it came with Catalina installed, so half the apps I use daily don't work any more. So, I need to downgrade. Have checked out a number of sites regarding it, and I get the general idea. I tried restarting it with Command+R, to see if I could reinstall from the Time Machine backup from my old Mac Pro, as that was one of the suggested routes. However, the SSD in the iMac isn't HFS, so that won't work. I'd need to create a bootable external drive, boot from that, reformat the internal SSD and the restore to that.

It just so happens that when I put an SSD into my old Mac Pro as the boot disk, I kept the old boot HD, just as it was, so that should be a bootable volume. My thinking is that I should be able to attach it as an external drive, select that as the startup disk, boot from it, reformat the iMac SSD to Mac OS (Journaled) with GUID Partition Map, restart without the old boot disk, and restore my old El Capitan system from the Time Machine backup.

Before I go ahead, am I missing something? Would that even work? I'd hate to end up with another brick... already had one of those this week when my 2008 3.1 Mac Pro finally expired.

 

[chrfr]

I just got my shiny new 27" iMac this morning, and it's a fabulous machine from what I can tell so far. Not so fabulous is that it came with Catalina installed

These computers can only run Catalina; there's no possibility to downgrade.

 

[profcutter]

As far as I know, the only new Mac that will run Mojave is an iMac pro, and maybe the mini. A refurb 2019 iMac is a solid choice.

 

[quatermass]

Oh... this is really bad news! Already got the machine, no way to get anything else. Arse!

 

[profcutter]

Can you return the one you got? Otherwise, you may be able to run Mojave in a Virtual Machine. If it’s a lot of your workload, though, that could be a real pain.

 

[itsmeaustend]

Virtual machines, friend! VMWare just made their basic software free to use, so good timing there.

Can you return the one you got? Otherwise, you may be able to run Mojave in a Virtual Machine. If it’s a lot of your workload, though, that could be a real pain.

Ehhh.... Depends on OP's computer. I have a 2020 27" too, and I can run 2 VMs simultaneously, both playing games (makeshift split-screen setup, don't ask lol). So they are very capable machines even when using VMs doing demanding things.

 

[Homy]

No, you can usually not downgrade a new Mac to an older system than the one it was delivered with.

 

[chrfr]

No, you can never downgrade a new Mac to an older system than the one it was delivered with.

That's not exactly true. You cannot downgrade a mac to an operating system older than what was shipped on the first of that particular model. For instance, the "2020" Mac Mini, which is really a 2018 Mac Mini, ships with Catalina, but you can install and run Mojave on these models without a problem because that's what first shipped on the 2018 Mini.

 

[chabig]

OP, have you considered updating your apps?

 

[Homy]

That's not exactly true. You cannot downgrade a mac to an operating system older than what was shipped on the first of that particular model. For instance, the "2020" Mac Mini, which is really a 2018 Mac Mini, ships with Catalina, but you can install and run Mojave on these models without a problem because that's what first shipped on the 2018 Mini.

You're right. I should have written "usually".

 

[quatermass]

OP, have you considered updating your apps?

I've updated or replaced all the important ones, or devised workarounds, but there's a couple, most importantly Strata, for which no updater exists. And that's my major problem.

 

[quatermass]

Virtual machines, friend! VMWare just made their basic software free to use, so good timing there.



Ehhh.... Depends on OP's computer. I have a 2020 27" too, and I can run 2 VMs simultaneously, both playing games (makeshift split-screen setup, don't ask lol). So they are very capable machines even when using VMs doing demanding things.

I've got an old version of VMWare Fusion, but it seems that doesn't work any more! The basic software sounds like it's worth a look, especially as I have a Mojave installer to hand - is that "VMWare Fusion Player"? Seems my machine is up to the task - it has 72MB Ram, which should be adequate!

 

[pmiles]

Didn't you say you had an old Mac Pro still? Seems the obvious choice would be to run Strata on it until they finally make a 64-bit version of the app. You always take a performance hit when running anything using VMWare.

The issue with trying to boot off an external hard drive running Mojave is the lack of driver support for your iMac hardware (it didn't exist pre-Catalina). So no display for starters.

Bootcamp is another option... but you'd need a Windows version of Strata and a Windows license. May end up having to do that at some point if Strata doesn't support ARM.

 

[r6mile]

Didn't you say you had an old Mac Pro still? Seems the obvious choice would be to run Strata on it until they finally make a 64-bit version of the app. You always take a performance hit when running anything using VMWare.

The performance hit on VMWare is only like 10% (last time I measured on geekbench), which would make it still many times faster on the new iMac than a 2008 Mac Pro. That's very much the way I would suggest to go.

 

[quatermass]

Didn't you say you had an old Mac Pro still? Seems the obvious choice would be to run Strata on it until they finally make a 64-bit version of the app. You always take a performance hit when running anything using VMWare.

The issue with trying to boot off an external hard drive running Mojave is the lack of driver support for your iMac hardware (it didn't exist pre-Catalina). So no display for starters.

Bootcamp is another option... but you'd need a Windows version of Strata and a Windows license. May end up having to do that at some point if Strata doesn't support ARM.

I still have the Mac Pro, but it's dead, Jim! Seems to be related to the backplane, after exhaustively testing all other possibilities. I might go and buy a Mac Pro carcass that has a functioning motherboard and transplant everything into that, so at least I have a working second machine. In the meantime, I'm trying the VMWare route. It doesn't need to be blazingly quick, I just need access to my existing models, and do some modelling/texturing. I mostly render in C4D which works fine in Catalina, but I prefer modelling in Strata.

 

[gilby101]

VMware Fusion is not currently the greatest for graphics intensive software (which I assume includes Strata). But there are hints that could change soon for VMware Fusion 12 running on Big Sur host along with recipe for how to do it now: https://www.vimalin.com/blog/fusion-12-0-metal-support/.

 

[DeltaMac]

I've got an old version of VMWare Fusion, but it seems that doesn't work any more! The basic software sounds like it's worth a look, especially as I have a Mojave installer to hand - is that "VMWare Fusion Player"? Seems my machine is up to the task - it has 72MB Ram, which should be adequate!

I might suggest that 72MB Ram would not be adequate for a VM. (I bet you do have more, just a typo, eh?)

 

[quatermass]

I might suggest that 72MB Ram would not be adequate for a VM. (I bet you do have more, just a typo, eh?)

It seems to be quite adequate! I've been running Mojave, using VMWare Fusion 11.5, running Strata CX 7.5 and Photoshop CS6 together quite happily. I gave it 3 cores, and 24GB RAM and dare I say it, it's every bit as usable and quick as my old Mac Pro. No, it's not a typo! It's the stock 8 + an extra 64gb, but I may get another 64gb as the prices are pretty good these days. Note to self - change sig!

 

[chrfr]

It seems to be quite adequate! I've been running Mojave, using VMWare Fusion 11.5, running Strata CX 7.5 and Photoshop CS6 together quite happily. I gave it 3 cores, and 24GB RAM and dare I say it, it's every bit as usable and quick as my old Mac Pro. No, it's not a typo! It's the stock 8 + an extra 64gb, but I may get another 64gb as the prices are pretty good these days. Note to self - change sig!

The person you're replying to is making fun of your typo, in which you typed that the computer had 72 megabytes of RAM.

 

[jms-uk]

It seems to be quite adequate! I've been running Mojave, using VMWare Fusion 11.5, running Strata CX 7.5 and Photoshop CS6 together quite happily. I gave it 3 cores, and 24GB RAM and dare I say it, it's every bit as usable and quick as my old Mac Pro. No, it's not a typo! It's the stock 8 + an extra 64gb, but I may get another 64gb as the prices are pretty good these days. Note to self - change sig!

8GB + 64GB does not equal 72MB

 

[DeltaMac]

Not trying to be pedantic here, but --- How is 72MB not a typo? When I last checked, 72 MB is (just slightly) smaller than 72 GB (NOT making fun, just curious )

 

[Fishrrman]

"I just got my shiny new 27" iMac this morning, and it's a fabulous machine from what I can tell so far. Not so fabulous is that it came with Catalina installed, so half the apps I use daily don't work any more. So, I need to downgrade."

As others have already told you... you can't.

If you (like me) have numerous 32-bit apps that you absolutely want to keep using, you have two choices:
Choice #1:
Return the 2020 iMac while you still can, and get an Apple-refurbished 2019 iMac. These will run Mojave and you'll be able to run your 32 bit apps with a "native boot".
Choice #2:
Use emulation software such as Parallels or VMWare Fusion, and install an older OS that way. You'll still have to BOOT the iMac "in Catalina", however.

 

[cltd]

Choice #2:
Use emulation software such as Parallels or VMWare Fusion, and install an older OS that way. You'll still have to BOOT the iMac "in Catalina", however.

Will old 32bite games (Call of Duty MW, Bioshhock etc.) run smoothly under virtual OS?

 

[quatermass]

Not trying to be pedantic here, but --- How is 72MB not a typo? When I last checked, 72 MB is (just slightly) smaller than 72 GB (NOT making fun, just curious )

Got it! That's what comes of doing three things at the same time... last time I had 72MB was in an Amiga...

 

[CheesePuff]

8GB + 64GB does not equal 72MB

yeah, you obviously know what they meant..