Hi,
To me this sounds as a PSU failure. I could bet my under pants it is.
It's either to weak for your setup or something broken. If its old it wont have the same juice as before.
Have had similar issues back in the days.
Try running games with only one card, then two.
On my Asus motherboard I can disable PCIe slots with switches on the board. Don't know if your can do that but try to remove the cards and disconnect the power from them.
Have a look here
http://www.guru3d.com/articles_pages/gtx_780_ti_sli_geforce_review,4.htmlIt says
Quote:
GeForce GTX 780 Ti 3-way SLI - On your average system the cards require you to have a 1200 Watt power supply unit as minimum.
And you have lots of other water cooling stuff & fans.
Quote:
What would happen if your PSU can't cope with the load:
Bad 3D performance
Crashing games
Spontaneous reset or imminent shutdown of the PC
Freezing during gameplay
PSU overload can cause it to break down
I believe you have to start looking for a new PSU.
Cheers!