MP 1,1-5,1 Graphics Cards seem to have died

[mitchino]

I have a 12 core 5.1 that I use for 3d GPU rendering with Octane. It has a 1080ti and a 980ti in it. The 980ti which is a mac version runs the monitor and the 1080ti does the rendering. The other day was getting graphics glitches on screen, so I rebooted the machine and zapped the PRAM. I restarted and all was ok for a while then the glitches returned. I took out both graphics cards so I could try each one on it's own. Now I can't get a display output from either one of them. Is it possible that both could have died at the same time? Anything I can do to test them? I've tried them in another mac and get the same result.

 

[m4v3r1ck]

How are both cards powered?

 

[mitchino]

The 980ti is powered internally and the 1080ti externally. The mac works fine with a Radeon 580 so the mobo must be ok.