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If I need to go back to High Sierra, how?

G

gadgetfreak98

macrumors 6502
Original poster
Sorry if this has been discussed before, but I messed something up (maybe) and am looking for how to avoid any further issues.

So I went on a little modernization spree with my 2009 (5,1) Mac Pro. Put in a new startup SSD, upgraded the CPUs and installed a Radeon RX580 card, after which I successfully installed Mojave. While all seems ok, I had intended to have a backup of my HS install just in case I needed to go back. However, my two clones both auto-updated overnight to my Mojave install (forgot to unplug the FW drive).

I have created an HS installer USB drive in case for some reason I want to go back... For instance, if I decide the the expense of the RX580 isn't worth it or I have issues with it.

My questions are:

1. If I use the USB installer, can I just install HS over the external clone that got updated to Mojave? Just trying to make sure before I'm too far into Mojave, I've got myself a backup plan (knowing I screwed up with the clone over night)

2. If future updates happen on Mojave (if I stick with it), will the GT120 still work if I need to swap it in to do OS updates, etc?

3. What are other things would I need to focus on undoing if I decide Mojave isn't for me?

Thanks!
 
gadgetfreak98 said:
Sorry if this has been discussed before, but I messed something up (maybe) and am looking for how to avoid any further issues.

So I went on a little modernization spree with my 2009 (5,1) Mac Pro. Put in a new startup SSD, upgraded the CPUs and installed a Radeon RX580 card, after which I successfully installed Mojave. While all seems ok, I had intended to have a backup of my HS install just in case I needed to go back. However, my two clones both auto-updated overnight to my Mojave install (forgot to unplug the FW drive).

I have created an HS installer USB drive in case for some reason I want to go back... For instance, if I decide the the expense of the RX580 isn't worth it or I have issues with it.

My questions are:

1. If I use the USB installer, can I just install HS over the external clone that got updated to Mojave? Just trying to make sure before I'm too far into Mojave, I've got myself a backup plan (knowing I screwed up with the clone over night)
Click to expand...
Yes, you can.

2. If future updates happen on Mojave (if I stick with it), will the GT120 still work if I need to swap it in to do OS updates, etc?
Click to expand...
GT120 is not supported with Mojave anymore. Once Mojave is installed, if you replace the RX-580 with the GT120, the UI will be unaccelerated - slow as molasses.

3. What are other things would I need to focus on undoing if I decide Mojave isn't for me?

Thanks!
Click to expand...
Do a backup, then just do a clean install of High Sierra. After that, copy your files from your backup and be happy.
 
Thanks for the swift reply! Very helpful.

To follow on this, in a separate thread, you gave me helpful advice about downloading the AppleDiagnostic Tool to check my RAM speed. This has to be done via a bootable USB stick, which I have now created. Is it possible to access that stick upon reboot in anyway without my GT120 in? Do I need to reinsert the 120 to be able to boot into that?

Thanks!
 
gadgetfreak98 said:
Thanks for the swift reply! Very helpful.

To follow on this, in a separate thread, you gave me helpful advice about downloading the AppleDiagnostic Tool to check my RAM speed. This has to be done via a bootable USB stick, which I have now created. Is it possible to access that stick upon reboot in anyway without my GT120 in? Do I need to reinsert the 120 to be able to boot into that?

Thanks!
Click to expand...
You need a Mac EFI GPU to run AHT, so no PC GPUs like RX-580.
 
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