The ¬NED pin goes low on detection of a nuclear detonation [pdf]

Re:The ¬NED pin goes low on detection of a nuclear detonatio... by wtallis on Monday October 31, 2011 @10:16PM (#3180257)

Aren't the mechanisms of Moore's Law (ie. smaller transistors that run at lower voltages) exactly the same things that make chips more susceptible to radiation? Once you compensate for that by including more redundancy, you may not have a cheaper chip.

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Re:The ¬NED pin goes low on detection of a nuclear detonatio... by Daniel_Newby on Monday October 31, 2011 @11:32PM (#3180494)

Yes. More dense, lower power chips are more susceptible to radiation.

And anyway, what exactly does "redundancy" mean? If a rocket engine controller is triple redundant, how does that work? Are there three propellant valves in parallel, so each computer controls one-third of the thrust? Are they in series, so that failure of one computer disables the propulsion function? Is there a majority vote system, and is it electronic, electromechanical, or fluidic? Redundancy is not pixie dust that magically makes your system design better.

A sample Google interview question is to design the protocols to run a cluster of unreliable computers. Should there be a MIL-SPEC master computer? Should the cluster elect a master? Or several oligarch servers? Where does an outside agent submit a request, and what does it do if the request is not answered. Designing reliable systems is hard.

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Re:The ¬NED pin goes low on detection of a nuclear detonatio... by nobody31 on Tuesday November 01, 2011 @12:07AM (#3180583)

Depends on the desired outcome.

For self destruct systems you probably want all three to agree before going bang - while for an emergency escape system you probably want any one of three to be sufficent to deplay.

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