MP 1,1-5,1 Mac Pro 5,1 - OC Ventura used to work, now it doesn't anymore

[Sartolo]

Hello everyone,
I just can't understand what went wrong with my Mac Pro 4,1>5,1 (dual cpu, 16 GB RAM, AMD R9 280 3GB flashed, High Sierra) so I try to explain every single step I followed in order to troubleshoot the problem.

1. I've first installed Mac OS Ventura following this tutorial:
   . Everything went as expected, I've installed the OS in a new Samsung SSD and for 2 days was all good;
2. Since I have a 4K LG monitor and I couldn't make it work at 60 hz, I've done some research and found out HDMI cable doesn't like 60 hz while DisplayPort does, so I managed to buy a mini DP - DP cable. Everything was smooth and fine with my high res and 60 hz Ventura OS;
3. Here's where it gets weird: I'm totally SURE the computer booted up at least for 1 more day with this kind of setup, the new cable and so on. The day after, by the way, computer didn't seem to boot in any possible way, there was just the chime and nothing else, no screen, no keyboard seemed to work so no possibile NVRAM reset, nothing at all. I've tried to boot it with the long press and still nothing, changed back my GPU to my GT120 (still mini DP - DP cable) and still nothing. In this phase I'm sure I managed to have the keyboard working somehow (though I can't remember how), so I've done a NVRAM reset (single reset, double reset, triple reset, everything was suggested online lol) but still nothing on the screen, I've even tried removing all the hdd and ssds and having just the High Sierra one, the answer was nope;
4. Searching here and there I've found that the issue was cable related, as Mac OS doesn't initialize with a Display Port configuration > 1.1 (so neither 1.2/1.4 are supported - my screen doesn't have 1.1); as strange as it seemed to me, the system booted up normally with HDMI and the AMD card, but I've somehow lost my boot screen (even if the GPU is flashed). This was pretty simple to fix, as NVRAM reset re-enables SIP, so with the GT120 again and an old DVI monitor I was able to get to the recovery, disable SIP and boom, I've got my boot screen back again with my AMD R9 280;
5. From now on, there's no way to get into Ventura OS again. Every time I boot into EFI Boot and select the OS, the infamous prohibited sign comes right on, with the link to the startup section on the Apple website. The strangest thing is I can't even reinstall Ventura: I've tried to boot it from the USB with which I've installed it, and I've even tried to re-build the USB with OC and try again, and the result is always the same prohibited sign, as if the Mac isn't able to boot into OpenCore anymore.

I've tried everything I could and still nothing happened since then, so I'm pretty sure I'm missing something, but I can't figure out what is it. Any help will be super appreciated.

 

[barkmonster]

It failed on my Mac Pro completely after working fine and updating several times all the way to 13.6. I never resolved it and even rolling back to Monterey didn't work. OC simply won't complete an install without an error at the final stage. I tried installing it on my Mac Mini and OC still did the same thing but at least it didn't with Monterey. I now run Catalina on my Mac Pro and I've given up trying to get anything higher than that installed.

 

[haralds]

Try to install OCLP from Catalina. Then install OCLP release 0.6.8 from that. Reboot Catalina under OCLP (reboot with Option down, select EFI Boot, select Catalina.)
Create your target Ventura volume, if you do not already have an install. If you do, install over it.
In either case, start the install from the OCLP booted Catalina.
You might have to reboot several times.

 

[Macsonic]

Hello everyone,
I just can't understand what went wrong with my Mac Pro 4,1>5,1 (dual cpu, 16 GB RAM, AMD R9 280 3GB flashed, High Sierra) so I try to explain every single step I followed in order to troubleshoot the problem.

1. From now on, there's no way to get into Ventura OS again. Every time I boot into EFI Boot and select the OS, the infamous prohibited sign comes right on, with the link to the startup section on the Apple website. The strangest thing is I can't even reinstall Ventura: I've tried to boot it from the USB with which I've installed it, and I've even tried to re-build the USB with OC and try again, and the result is always the same prohibited sign, as if the Mac isn't able to boot into OpenCore anymore.

I've tried everything I could and still nothing happened since then, so I'm pretty sure I'm missing something, but I can't figure out what is it. Any help will be super appreciated.

About the prohibited folder sign, this happened to me at one time. What I did was when starting up the computer, I first press the Option key so the Legacy Apple boot screen appears. Your GPU should be able to provide a boot screen. Then, seeing the EFI HD Icon on the Apple Legacy boot screen, select the EFI HD and press the “Control” key and click. Upon restarting, was able to boot to the Opencore boot drive. Please note this worked in my case and hope this works with you too.

I would always keep an extra, duplicate copies of OCore Catalina, Big Sur in extra SSDs as backups. So it’s easy to go back in case of problems. If it’s a new OS like Ventura, would install this on an extra SSD for testing and retain my main working drive.

 

[Sartolo]

About the prohibited folder sign, this happened to me at one time. What I did was when starting up the computer, I first press the Option key so the Legacy Apple boot screen appears. Your GPU should be able to provide a boot screen. Then, seeing the EFI HD Icon on the Apple Legacy boot screen, select the EFI HD and press the “Control” key and click. Upon restarting, was able to boot to the Opencore boot drive. Please note this worked in my case and hope this works with you too.

I would always keep an extra, duplicate copies of OCore Catalina, Big Sur in extra SSDs as backups. So it’s easy to go back in case of problems. If it’s a new OS like Ventura, would install this on an extra SSD for testing and retain my main working drive.

Tried this trick but it didn't actually restart, nor in the Apple Boot screen neither in the EFI boot screen.