Mac Pro 3.1 with GTX 770 won't boot I was given a MacPro 2008 with 1 CPU, 1TB hard-drive, no wifi and 6GB of memory.

I patched via DosDude1's patch tool so enable NVME.

Current Specs: 2x4core 3.2Ghz. Wifi, 32GB of RAM, PCIe/NVMe Samsung 512GB.

Updated the OS to Mojave.
All is well. the machine is fast.

Tried to install the GPU (GTX 770), which is supposedly natively supported in Mojave

Slot 1- New GPU

Slot 2- PCI/NVMe

Slot 3- Old GPU


With OLD out and monitor plugged into NEW - Nothing
With OLD IN and NEW in , monitor plugged into OLD - Hangs at status bar 50%
OLD IN, NEW OUT - Boots no problem
There are no drivers for NVidia 3rd party cards in Mojave.
Support ended at High Sierra.

MacVidCards - Which driver should I install for my new GPU?​ is pretty much the authority on this topic. 

You can get to Mojave if you have a supported* ATI/AMD GPU with Metal capability, otherwise stay on High Sierra.

*Recommended GPU list, again from MacVidCards - I want the best graphics card for my Mac Pro, where do I start? No 3rd party drivers are needed for AMD cards, they still have Apple support - but only to Mojave, no further, for Mac Pro 3rd party cards.