Firmware update not working on MP 5,1

[Mister Speaker]

I'm finally getting around to upgrading from Sierra to HS (and further, ideally) for some streaming hardware I'm getting soon, and remembering that last time I tried this upgrade I hit a snag: The firmware updater won't work; it returns to the same "please restart to complete installation" screen.

Last time I went looking for answers and found that the most likely culprit is the aftermarket GPU in the machine and finding the native card and putting it in should allow the firmware update to go through. But The aftermarket card is 'metal-supported' and others were saying this means it should work fine. I think the other possibility was my boot drive being an SSD on a PCIe card.

What are my options here? I guess I should probably order the native GPU just to have around. If it's not the GPU and it turns out to be the SSD issue, can I pull the drive, stick it in a USB3 drive caddy? If the drive caddy is connected also through a USB3 card on the PCI bus, is that going to be a problem? Best practice just to stick the drive in the optical bay?

Thanks for your time.

Mac Pro 5,1 (mid-2010)
Radeon RX580 (native card would be a 5770, I think)
2x OWC 1TB SSDs on PCIe cards
2x OWC 1TB SSDs in optical bay

 

[Macsonic]

Sorry to hear about your problem. There’s another guy in the video below who tried updating the firmware to install High Sierra on his 5,1 2010 Mac Pro. He also had a problem updating the firmware but came up with a solution. Maybe his fix might work on your end.

 

[MarkC426]

What is your current firmware version?

 

[Macsonic]

My firmware version is 144.0.0.0.0 I'm running 3 OSXs, Sierra, High Sierra and Mojave. Each OSX's are on 3 different HDs.

 

[MarkC426]

Sorry Macsonic, my question was to the OP......
I am thinking he might be on an old FW and can’t update without an EFI card.

 

[Macsonic]

Oops, no problem, MarkC426. Thanks