@Gaetan thanks for the tip, I didn't know that (good) tool.
Last crash (with case close) doesn't see any anormal temperature, have to try again.
Maybe I was just lucky during my test with open case....
What is the main objective of the "step by step OC" ? Seeking the maximum value of the OC for each pi or try to stabilized the OCing mode ?
P.S.: my objective (and test) : running goldeneye64 (it seems to work but only at 1500).