MP 1,1-5,1 mac pro 5,1 mid 2010 - attempted OS downgrade Mojave to High Sierra...ends badly

[aaronbailey]

This mac pro was running 10.14.0 Mojave without any issue running/booting/displaying

prior to attempted downgrade to 10.13.6 High Sierra.



I backed up the mac.

I then erased the HD in preparation for the 10.13.6 install.

i created a bootable usb of 10.13.6 High Sierra from another Mac Pro to

ultimately install that OS version on the mac i just wiped.



….this is where things went bad.



The mac started up with chime and everything visibly is working, sounds like its working exactly as it always has.

trouble is i don’t get anything on my 4k display. I essentially have no way to access that mac.



I assume everything is functioning correctly as normally. i had a local tech company diagnose the problem and they think the issue with the Asus Geforce GTX 670 direct cu II’s pre-boot software/driver etc. being gone? deleted?



How do i get out of this jam? How can I can i get this mac pro back up and running even if i have to abandon the OS downgrade to High Sierra and get back to working with the Mojave OS that was working perfectly before i started ticking around with this thing??!! Im obviously WAY outta my league here and i need some tips to un-f this thing up..



Mac Pro 5,1 (mid 2010)

intel processor

32 gb ram

Asus Geforce GTX 670 direct cu II

Mercury Electra 6gb SSD

Samsung 28” 4k display



TIA - Marc

 

[tsialex]

i had a local tech company diagnose the problem and they think the issue with the Asus Geforce GTX 670 direct cu II’s pre-boot software/driver etc. being gone? deleted?

If the GPU had pre-boot support before, it's probably a flashed one, since only the eVGA GTX 680 MacEdition had pre-boot configuration support from factory.

Most flashed GPUs (at least all GPU flashed from eVGA GTX 680 Mac Edition derived EFI firmware) don't provide pre-boot configuration support if you are using a display that connects via DP1.2 or newer.

Seems that you are connecting via DP1.2 or 1.4, since you are using a 4K diskplay. I'd start installing an AppleOEM GPU + a DVI display and see if the Mac Pro works.

 

[aaronbailey]

If the GPU had pre-boot support before, it's probably a flashed one, since only the eVGA GTX 680 MacEdition had pre-boot configuration support from factory.

Most flashed GPUs (at least all GPU flashed from eVGA GTX 680 Mac Edition derived EFI firmware) don't provide pre-boot configuration support if you are using a display that connects via DP1.2 or newer.

Seems that you are connecting via DP1.2 or 1.4, since you are using a 4K diskplay. I'd start installing an AppleOEM GPU + a DVI display and see if the Mac Pro works.

Thanks for the reply,

I took your advice and I bought and have installed an ATI Radeon HD 5870 - 1GB Graphics Card,
Connected it to an older DVI display and the Mac works. It starts up, with the chime and immediately I get a blank gray screen. After a minute or so I get the dreaded flashing folder with the question mark.

I have tried many key commands at start up to try to get the Mac to find its boot software with no success.
I have made both Mojave and High Sierra bootable files on a usb flash drives and still not able to find its startup software.
I know that all of the MACs components are working and operational ie. HD, power supply etc.
So i think this most certainly a software/configuration issue.

any idea what my nexts steps should be?
Thanks again

 

[tsialex]

Thanks for the reply,

I took your advice and I bought and have installed an ATI Radeon HD 5870 - 1GB Graphics Card,
Connected it to an older DVI display and the Mac works. It starts up, with the chime and immediately I get a blank gray screen. After a minute or so I get the dreaded flashing folder with the question mark.

I have tried many key commands at start up to try to get the Mac to find its boot software with no success.
I have made both Mojave and High Sierra bootable files on a usb flash drives and still not able to find its startup software.
I know that all of the MACs components are working and operational ie. HD, power supply etc.
So i think this most certainly a software/configuration issue.

any idea what my nexts steps should be?
Thanks again

Remove all disks from your Mac Pro (USB/FW/PCIe/SATA), disconnect the DVD.

Fully erase the disk you want to install 10.13.6 with another Mac with the Terminal command sudo GPT destroy diskXX - you will need to find the real disk node instead of the diskXX. Install back just the nuked disk and the createinstallmedia installer, let the Mac Pro boot from the USB key - takes around three to five minutes for the Mac Pro firware scan everything and then go into fail-safe mode and automatically boot the createinstallmedia installer.

Since you can't access the BootPicker, it's very probable that you gonna need the BootROM reconstruction service, I'll send you a PM.