Thermal protection is a feature of x86 microprocessors which stops the processor when it exceeds a critical temperature to prevent permanent damage. AMD CPUs report if the feature is supported with the 'TTP' flag in CPUID leaf 8000_0007h. The processor notifies motherboard logic with the THERMTRIP signal, active low, if the thermal protection circuit has tripped. The motherboard is supposed to power off the processor in response and a system reset is necessary to leave this state.