Mac Pro 4,1 nvidia 660 NO BOOT OS

[izapp]

I just received a Mac Pro 4,1 8core from ebay.

It came with ATI HD 4870 512 MB GPU. I bought an EVGA GTX 660 OC 2GB.

When I unboxed the Mac today I installed straight away the 660 and it booted and worked fine. The Mac pro was loaded with 10.8 OS and I upgraded to 10.9. When I installed 10.9 when it first restarted it never booted.

What is the issue here? When I was on 10.8 of course I did not have a boot screen but when I upgraded it never loaded the OS.

I would appreciate your help

Thank you for your time in advance

 

[Parigot]

Did you try to put back the original video card and give it a try?

 

[izapp]

Did you try to put back the original video card and give it a try?

Yes, of course. I am running 10.9.5 now with the original card. I just updated 10.9 to 10.9.5. Maybe lack of updates was causing the problem? I have not tried installing the new nvidia card since I updated

 

[Macsonic]

Yes, of course. I am running 10.9.5 now with the original card. I just updated 10.9 to 10.9.5. Maybe lack of updates was causing the problem? I have not tried installing the new nvidia card since I updated

Not sure what could be the problem. Your 660gtx should work fine even without a boot screen There is a video HERE about a guy who linstalled an Nvidia non-flashed card on his 2009 Mac Pro.