In a computer system that includes processing, memory and I/O modules and ACPI for outputting an ONCTL signal to a power supply unit. The power supply is configured to output a power off signal indicative of power off state and power on signal indicative of power on state. There is provided an embedded controller coupled to the ACPI and to the power supply unit. The embedded controller includes input for receiving a shut off event and in response to the shut off event, feeding to the ACPI a controller power off signal as long as the power supply is in power on state.