Because Sierra came before Mojave...

Glad to hear you learnt something, but it's irrelevant to the thread title.
It's about hardware and firmware and HS.

 

I can't run Mojave since it requires a metal capable GPU. I just want to update to High Sierra.

 

Yes, I understand, I wish you good luck!

 

the concern is not wiping the drive, and perhaps this "SSD mounted to a Sonnet Tempo SSD Pro Plus Dual PCIe 2.0 Card.". I have the same 5770 radeon in mine but everything else is pretty different. it is 2.4ghz dual Xeon model.

I am googling a product to use gps satellites to control my dog with smartphone app. we should be able to figure out a 11 year old computer.

 

Last edited: Sep 22, 2021

I managed to do the firmware update. My Boot-ROM-Version is on MP51.0089.B00 and the High Sierra Installer works now. But when I reach the Choose Volume stage, it won't let me choose my boot drive (also not the other SSD) saying again: "Installation on this volume is not possible, because computer is missing firmware partition." I'm going crazy with this shiieeet!

 

can you do diskutil list in terminal and df -h

here's one good post about this. tldr, your computer. EFI related?

https://www.ifixit.com/Answers/View...volume+because+the+computer+is+missing+a+firm

I think you are possibly still stuck at wiping stuff.

 

Last edited: Sep 22, 2021

Cannot Install Because the Computer lacks the Firmware Partition.

https://translate.google.com/transl...da-dem-computer-eine-firmwarepartition-fehlt/

Please use the Google Translator - its a german Language Webpage:
https://www.hackintosh-forum.de/for...da-dem-computer-eine-firmwarepartition-fehlt/

 

Yes, google that line "You may not install this volume because the computer is missing a firmware partition"
-Next to @clone's iFixit link, a couple of others answers show up. I also think this Sonnet enclosure could be part of the problem.
Other then that, InsanelyMac & Netkas forum are the places where Mac geeks go, you could get some expert help over there.

 

Glad to see it worked out.

You might have to install some kexts and disable some security features in order to make that PCI enclosure work as boot drive.

Good Luck.

 

thanks, man!! Everything worked just fine. It booted right from the same SSD after installing it on/the PCIe again.