Okay, update for those having issues with mixed nvidia/amd rigs I just discovered this yesterday. Both of my mixed rigs are using the same motherboard (Asrock h110 pro) Additionally both MB's had 2 sticks of 4 GB memory plugged into them, so on a hunch I pulled 1 stick of 4GB Ram out and left them with only 4GB of ram. Not sure WHY this would make them more stable but both have been running fine now for over 24 hrs with no freezing or shutoffs.. If this can help anyone else I hope it does, maybe those MB dont like 2 sticks of RAM I dunno but so far it's seemed to work with 4.9b.