GTX 750ti boot with tripple screen setup booting problem

[dreadkopp]

Hey Community,

 

for the sake of my electricity bill i switched my old HD6870 for a GTX750Ti.

 

That might have been a bad idea as it seems.

 

It's an Asus Strix 750ti 4GB that comes with 1x HDMI, 1x DVI and 1x DP.

 

I have one Monitor connected to each of the outputs.

 

Currently running 10.12.3 with clover 3974, smbios of iMac14,2

 

My Problem:

 

When i boot with all three monitors connected instead of login screen all three monitors will only show black screen.

 

i used iMac10,1 smbios before and could only boot with one monitor connected, after switching to 14,2 i can boot with two ...

 

DVI + DP as well as HDMI + DP works, HDMI + DVI or HDMI + DVI + DP does not work.

 

When i boot with only two Monitors connected and attach the third after login screen showed up it is detected correctly and my tripple monitor setup is fully usable.

 

 

using nvidia web drivers, nothing else.

 

If this would have been a AMD card i'd say i alter the frame buffer, but what to do with a Nvidia Card?

 

Really hope someone has a idea how to fix this.

 

 

Cheers