Possible to run 32-bit apps to a Catalina machine using an external boot drive?

[CoffinJoe]

Hi guys, I'm not sure if this is so much of an OS question as it is a hardware/computer one, hopefully you can point me in the right direction:

I have a newish 2019 MacBook Pro that I got in Nov. 2019 that came preinstalled w/ Catalina (which for better or worse is why I'm posting here). I'm curious if I can create an external drive running an older OS (possibly El Capitan) that I can use as a boot drive to run some older applications that either no longer work on Catalina, or have become subscription-only?? (so basically, running 32-bit applications on a 64-bit laptop, possibly off a USB-C SSD). My internal 500GB drive doesn't seem to be big enough to comfortably reformat and partition, hence the external.

I've never done this before, and have called around to a few 3rd part Mac retailers/service centers to see if it can even be done. One place suggested that I simply can't run 32-bit applications on a 64-bit machine, while others enthusiastically suggested they could do the job. Still, I don't want to plunk down a bunch of $$ to buy a drive, potentially pay some place to create the boot drive (yes, I'm sure I could do it myself if I Google around), only to have none of the apps work.

Have any of you done this? Is it possible? Or are there specific Threads-- here or elsewhere-- you've seen that have already discussed this, or that would be better suited for discussing this?? Thank you.

 

[ian87w]

If the MacBook was launched with Catalina as its first OS, I doubt that older macOS will support the hardware. I don’t think it’s doable as the older OS might not have drivers needed by the newer hardware.

And I don’t know if macOS would behave like Windows. On Windows, if an older Windows is installed on a newer machines, some components might not work due to new drivers not available for the older Windows, but there’s enough legacy generic driver that the computer will at least have basic functions. Not sure if macOS behaves the same.

 

[CoffinJoe]

Appreciate the response, hmm be good to hear from anyone though who may have tried doing so, successfully or not.

But yes I have heard that for some file types and software-- i.e. Quicktime 7, FCP7, CS5-- video codecs would be an issue/not run on modern NLE systems, just don't know if these programs would be unable to run at all using a newer machine.

 

[DeltaMac]

The hardware has been 64-bit since early in the Intel processors - all are 64-bit since 2007. The operating system (the software) has provided support for 32-bit apps, until that support was dropped in Catalina.
If you are using a Mac that never shipped with a macOS system older than Catalina, then the only choice that you have is to run 32-bit software in a VM running an older version of macOS.
Unfortunately, your "new" Mac, if it doesn't support something older than Catalina, then that means that you can't simply boot to an older system, regardless of whether the boot drive is internal or external.

But, you did not say which MBPro you have.... The 2019 16-inch is the only one sold in Nov 2019 that does not support a system older than Catalina. Maybe you get lucky, and you have a 13-inch or 15-inch MBPro. Those will be simply a matter of installing Mojave, and using your 32-bit apps.
You did mention CS5 - yeah, that's not going to work unless you go back to a bit older system, last system that completely supported CS5 was OS X 10.6.8 (apparently 10.12 (Sierra) is possible, but not supported by Adobe on CS5) - definitely won't work on your MBPro without using a virtual machine (VM) solution of some kind.
I would suggest that your easiest path would be to purchase an older MBPro that fully supports the software that you need to use. That will be much simpler in the long run, IMHO.