Thank you nick2006 for your help. i did what you told me and i saw a little better stability. with Prime95 for 2 hours no errors at all. but in CPU Stability Test in 3 minutes i had errors. here a screenshot:

Also nick2006 i see in Real Temp the core 1 always stuck at 40c and my temp is 45c at idle at 3150Ghz. is it right the temp for me? i have a watercooling solution and with my old QX6700 the temp was 28c at idle.
whats your temps at idle and full load? also when i test the sensors i see the core 1 at 0(stuck). do i have to worry about this? or i should RMA the cpu?
here a screenshot from Real Temp:


Thank you nick2006 Be well!!!

Spiros!!!