MP 1,1-5,1 Mac Pro 3.1 Does not boot from USB by pressing Option

[Pit París]

Good afternoon,
I'm trying to boot from a bootable USB and it's impossible. The keyboard works correctly. For some reason that I don't know, it doesn't allow me to boot from an external element. I appreciate the help you can give me. I have tried it with El Capitan and with another disk patched with High Sierra.

 

[arw]

What do you see on the screen when booting with the Option (⌥) or Alt key pressed: The native bootpicker but only your internal install? Nothing? An error?
Has it worked before?
- Do you use a cable-based USB keyboard directly plugged into a USB port of the motherboard/front?
- Is the bootable USB drive directly plugged into a USB port of the motherboard/front?

 

[Pit París]

I answer your questions by copying them

What do you see on the screen when booting with the Option (⌥) or Alt key pressed: The native bootpicker but only your internal install? Nothing? An error? Nothing, The screen remains black and the computer turns off
Has it worked before? No. Only USB works for storage
- Do you use a cable-based USB keyboard directly plugged into a USB port of the motherboard/front? Yes, original keyboard
- Is the bootable USB drive directly plugged into a USB port of the motherboard/front? Yes

Thanks a lot

 

[joevt]

Nothing

Do you have a GPU with Mac compatible firmware (requires UGA graphics for old Macs like the Mac Pro 2008)? If not, then the Apple Startup Manager (hold option at boot) won't be able to draw to the display. In that case you could try booting into RefindPlus which will know how to draw to the screen (using GOP instead of UGA). Then from there you can select a boot item from the USB.

 

[Pit París]

Do you have a GPU with Mac compatible firmware (requires UGA graphics for old Macs like the Mac Pro 2008)? If not, then the Apple Startup Manager (hold option at boot) won't be able to draw to the display. In that case you could try booting into RefindPlus which will know how to draw to the screen (using GOP instead of UGA). Then from there you can select a boot item from the USB.

The graphics card is an HD5770. I have another MP 3.1 and I was able to install Catalina without problem. I don't know what's happening to this Mac, it's the first time something like this has happened to me. The only thing I can think of is to put the graphics card (GTX 770) from the other Mac and try. However, having installed Capitan from scratch, inserting the pendrive and turning on the Mac, I think the problem is more complicated.
I'm looking into your solution, thank you very much.

 

[Pit París]

Do you have a GPU with Mac compatible firmware (requires UGA graphics for old Macs like the Mac Pro 2008)? If not, then the Apple Startup Manager (hold option at boot) won't be able to draw to the display. In that case you could try booting into RefindPlus which will know how to draw to the screen (using GOP instead of UGA). Then from there you can select a boot item from the USB.

You are right, the problem is generated by the graphics card. I installed the other graphics card (GTX770) and Monterey was installed without problems. What I can't understand is why the HD5770 works correctly with El Capitan and High Sierra, with a normal startup screen. but it generates problems when working with a bootable USB to select the boot.