Thanks for replying so fast
unfortunately, the system freezes completely, so neither local terminal, ssh or ipmi react only unplug the power supply is possible.
Can I find logs after a reboot? I will try to install ubuntu today to rule out a hardware error.
Which asrock board do you use? I've got more bitt of those, after I have annoyed the support for 2 weeks, they have told me that my board has no layer on the pcb for the igpu - but probably they use a c236 which should support this - manufacturers documentation is frustration :D