well....
i think my cpu just degraded in 5 mins 1.5v-1.6v vcore...
it used to be able to do at least 5 mins prime stable at 4320mhz at 1.368v vcore (as the pic shows on the top). now for the same clock, 4320mhz, prime stops even at 1.392v...
another possibility might be i take out my watercooling and went back to air cooling after the 1.5v-1.6v abuse. temp went really high (about 75c) when full load.
so now i am not sure, whether the high temp or the high voltage degraded my cpu...
guess its time to get a new one..