When the rig is shutting down, i have the debug led code 73 and never shutdown, is a loop. So I am very sure that problem is the SLI configuration.
I put one card working alone, and the PC, motherboard working perfect. So I put again both cards working together and same problem.
How to fix it?
Well I did various testing, change the position of the videocards and put in diferents slots, and the PC working good.
In my last test, I put again the video cards on the slot 1 and 2, clear the CMOS an leave the configuration by defect.
I changed in the BIOS the profile of the memory in 2666 MHz, operating sytem-other, not more Windows 8 WHQL, screen logo-enable, save and reset the configuration. After that reinstall nvidia drivers.
And my PC working good.
My system
I7 5820K @ 4.2GHz.
X99 Gaming G1 Wifi F9 Bios.
4x4 Kingston Predator DDR4 2666MHz.
2 Evga 780Ti ACX SC.
M2 Kingston Hyper X Predator 240GB