Sorry I missed it before when you unlock cores it sends your core temps crazy (I think thats the technical term) so you need to look at the CPU temp using a program like HWMonitor. The blend test as it says mainly tests RAM so try memtest to see if the RAM is stable. If it is run the prime 95 test that says maximum heat I can't remember what its called and it should crash quicker. Assuming it does go into the bios and try setting the CPU voltage to 1.45V and run prime 95 again. If this sorts it out try lowering the voltage as far as you can staying stable.
Increasing the voltage increases the heat produced and shortens the life of the CPU. As long as you keep the voltage under 1.5V and make sure the CPU temp stays under 60C then any shortening of the life should be limited until well after it is seriously outdated.