i tryed to reinstall windows 7 64bits, flashed original bios in gpu and claymore works good.

But in the moment i put moded rom with polaris editor (only changed mem frequency, core clock and mv) and another time the same problem, all with 16.9.1 latest driver. the claymore detect with 3GB and don't work another time.

In polaris i dont changed nothing important i backup original bios, opened and changed setting with conservative setting for test first if works and modify bios more times for see what is the max settings with stability.