I've the exact same reboots and I also noticed that's when the system idle, but it occurs almost every nights now .
Nov 25 15:05:46 nixos kernel: mce: [Hardware Error]: CPU 15: Machine Check: 0 Bank 5: bea0000000000108
Nov 25 15:05:46 nixos kernel: mce: [Hardware Error]: TSC 0 ADDR 1ffff9e2d67b0 MISC d012000101000000 SYND 4d000000 IPID 500b000000000
Nov 25 15:05:46 nixos kernel: mce: [Hardware Error]: PROCESSOR 2:800f11 TIME 1511618719 SOCKET 0 APIC f microcode 8001129
I also need help, because I use my machine for hosting some server ...
I think this is a know problem. I have similar reboots with my 1800X. I haven't found a solution yet.
It is discussed in the infamous gcc compile bug thread, see , but I belive this is another unrelated hardware bug. I think it is also discussed here: .