MP 1,1-5,1 MacPro 5,1 trying to downgrade to Mojave

[byke]

Hi there,
I am hoping that someone could offer some advice to a novice in this area.
I have a MacPro 5,1 that I purchased second hand.
The machine came with Catalina already installed, so I am guessing its been modified?
So I bought a new drive, removed the drive with Catalina in it - And tried to install Mojave.

At this point I am informed that Mojave cannot be installed, and a firmware update needs to happen.
And to press the shut down link.
At this point the shut down link doesn't seem to work, and rather than risk a future regret I thought I would ask if anyone has any ideas?

Cheers

 

[tsialex]

You probably have a NVIDIA GPU, or a GPU that only works with Catalina, no? Read the first post of the thread below:

MP5,1: What you have to do to upgrade to Mojave (BootROM upgrade instructions thread)

Please fully read this first post, you will probably find that you have one or more problems described into the various notes below. Mojave will only install if you have upgraded your BootROM to the current release and your Mac Pro have a Metal capable GPU*. If you are trying to install Mojave...

forums.macrumors.com

You need to install Sierra (no firmware upgrades needed) to make your Mac Pro work again, then you can do all the firmware upgrades required for High Sierra/Mojave - see all the info in the post I've linked above.

 

[byke]

Thank you so much, I have a radeon 590 (8gb) at present.
I received the Mac with the stock Mac shipped card originally (I cant remember the name) but changed it to this 590.
But I will try switching the card out and try installing Sierra and then upgrade from there.

Many Thanks

 

[tsialex]

Thank you so much, I have a radeon 590 (8gb) at present.
I received the Mac with the stock Mac shipped card originally (I cant remember the name) but changed it to this 590.
But I will try switching the card out and try installing Sierra and then upgrade from there.

Many Thanks

Should work.

Install Sierra and if the EFI firmware/BootROM of your Mac Pro is MP51.0089.B00, you can then download and open the current Mojave installer, this will get you to 144.0.0.0.0. If it's lower than MP51.0089.B00, you need to first upgrade to it with High Sierra current installer. Do not use old saved installers, macOS installers expire.

All details are on the first post I've linked. You can get past macOS releases from Apple here:

How to download and install macOS - Apple Support

Download and install current or previous versions of the Mac operating system on compatible Mac computers.

support.apple.com

 

[byke]

Should work.

Install Sierra and if the EFI firmware/BootROM of your Mac Pro is MP51.0089.B00, you can then download and open the current Mojave installer, this will get you to 144.0.0.0.0. If it's lower than MP51.0089.B00, you need to first upgrade to it with High Sierra current installer. Do not use old saved installers, macOS installers expire.

All details are on the first post I've linked. You can get past macOS releases from Apple here:

How to download and install macOS - Apple Support

Download and install current or previous versions of the Mac operating system on compatible Mac computers.

support.apple.com

Thank you so much for your insight.
May I ask, is there any reason why it wouldn't be possible to make a USB flash drive to load Sierra onto and to then install it onto a new SSD drive?
I have downloaded Sierra, but I am finding that when I try to create a boot flash drive in Catalina it just hangs and nothing is created. I attempted this on my 5,1 Mac.

I also tried to do it on my M1 Mac mini, and was also unable to get anywhere.
Cheers

 

[tsialex]

Thank you so much for your insight.
May I ask, is there any reason why it wouldn't be possible to make a USB flash drive to load Sierra onto and to then install it onto a new SSD drive?
I have downloaded Sierra, but I am finding that when I try to create a boot flash drive in Catalina it just hangs and nothing is created. I attempted this on my 5,1 Mac.

I also tried to do it on my M1 Mac mini, and was also unable to get anywhere.
Cheers

Sierra installer is a executable package, you need to run it, after that it will decompress and install to /Applications.

I've downloaded it last week with my MacPro6,1 + Monterey, runs fine then it's just to run createinstallmedia to make a USB installer, successfully created one here.

 

[byke]

@tsialex : Cheers, your help has been amazing.

For anyone else reading this thread and having problems.
I found that when I downloaded Sierra from Apple, that I was unable to create a bootable USB.
As there was some type of error.
I googled the error and found a MacRumors thread about the issue from a few years ago, which include some terminal coding that helped fix something related to plist ? anyway, it appears that the software from apple is not working straight out of the box and needs this plist change to work. And given that the issue has been listed for a long time, and no change to fix the issue , I doubt that it will be repaired by apple (As it is so old now)

I got it working, after a lot of tinkering.
But it wasn't easy sailing.

Cheers