New Graphics card without OSX

[equationse]

Hi,

Just bought a new graphics card, EVGA Nvidia Geforce GTX770. I have no OS on my Mac PRO 3.1 How can I install OSX and how can I install GPU driver. I tried to install OSX on a USB external SSD but the Mac is not booting up. I just have a black screen. This is a non-flashed GPU. And by the way...how can I flash my graphics card in 2017? Because tools for flashing in no longer supported by developers.

Thank you!

 

[Filin]

GTX 770 can't be flashed at home (for now). Contact MVC for this procedure
http://www.macvidcards.com/store/p81/Nvidia_Flashing_Services.html

Install macOS with your old stock video card and then replace it with new GTX 770

 

[equationse]

Well I bought the mac without any GPU...

 

[pastrychef]

If you have access to another Mac, you can do a clean install from that Mac and transplant the drive back to your Mac Pro.

 

[Filin]

Well I bought the mac without any GPU...

My advice - change GTX 770 to GTX680, it has nearly same performance, but you can flash it yourself with EFI bios and have normal boot screen.

Read this thread to choose right model https://forums.macrumors.com/threads/confirmed-and-possible-flashable-gtx-680-models.1578255/