Airplanes have always had circuit breakers, which are essentially thermal switches that open when too much current goes through a circuit, as can happen in a house when a wire comes loose in a lamp, say, or insulation gets frayed.
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Thermal switches on microprocessors often stop only the fetching of instructions to execute, reducing the clock rate to zero until a lower temperature is reached, while maintaining power to the cache to prevent data loss ( although a second switch, with a higher triggering temperature, usually turns off even the cache and forces the computer to reboot ).
