GTX 980 does not support mapped memory error

Mart1n71

My system is using a GTX 1070 and a GTX 980, which worked together, or individually quite well until yesterday. I modified a scene I was working on so it would fit on both cards, but Daz went immediately to CPU and the display driver crashed. Restarted PC and repeated, same result. Tried a different scene that I know to have worked on both cards previously, same result, driver crash, fall back to CPU. Even just a primitive sphere in an empty scene causes an out of memory crash and cpu render. 

If I now uncheck Optix Acceleration, I get my 1070 back, but the 980 is returning an error saying ‘device cannot be used as it does not support mapped memory (canMapHostMemory)’. I didn’t have a problem with it yesterday. Feeling frustrated.