After upgrading the microcode, I did not make any change to the BIOS settings.
As far as I remember, it is running the BIOS defaults.
As you can see in my previous post, I have C-states enabled.
It is common pratice to try disabling some C-state in case of stability problems ; especially disabling states C6 and higher.
However, in this particular case, I do think it is not related.
I will check my BIOS settings and will let you know.