MP 1,1-5,1 Mac Pro 5,1 Boot Rom Update failing

[Kouhee]

Hey

running 10.13.6 right now.
I´d like to keep this HS startup disk and install Mojave and then 10.15 onto a fresh SSD and then be able to see the boot screen switch back and forth between the two systems.

Apple is telling me(and every video i watched) to just press and hold the power button and the Boot Rom should be upgraded to the required version for Mojave(144 something?)

But it doesn´t.....power button light is flashing, i get the tone, but then it just stays on the same Boot Rom version.
What am i doing wrong? Im not too tech savvy, i did try to read a few guides, but getting confused/lost on the way.
Any simple instructions/guides to this problem available anywhere?

I do have a RME RayDat card and UAD card installed as well as several SSDs - could these really be the culprits?

Machine:
Mac Pro 5,1 Mid 2010
CPU : 2x3,46 6-core Intel Xeon
GPU : RX 580 8192 MB
OS : 10.13.6 High Sierra
Boot ROM Version : MP51.0089.B00

Thank you in advance

Cheers

 

[Bigwaff]

The definitive thread…

MacPro5,1: What you have to do to upgrade to Mojave (10.13/10.14 BootROM upgrades 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

 

[Kouhee]

Ok....so Mojave installer will update the Boot Rom, that was the mistake, i didnt shut tdown from the installer window.
Now....after that is finished, will it automatically instal Mojave over my High Sierra system?? Or can i 100% choose on which disc Mojave will be installed(The fresh SSD)

 

[Borowski]

No, after firmware update you can interrupt the installing process.

 

[MarkC426]

As @Borowski states above….
Once the FW updates you can cancel the install of Mojave if you like.
Then install Mojave later to a preferred location.

Alternatively run the Mojave installer, choosing your new ssd location.
The FW will be updated with this installation.

In order to go beyond Mojave, you will need to use OpenCore.