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Doesn't it seem like, as part of the engineering part of this project, that they would have a system in place that would sweep through and do a comparison for "
by bprater 16y ago
Doesn't it seem like, as part of the engineering part of this project, that they would have a system in place that would sweep through and do a comparison for "flipped bits" and, if found, would keep a clone of what the memory should look like and reset those bad bits? What happens when the flipped bit causes the machine to rotate out of communications view? You would basically be dead in the water without a failsafe system like this. What am I missing?
- jerf 16y agoThis is Voyager 2. Launched 1977. This wasn't an era where you could accidentally lose 8GB because it fell out of your cell phone and subsequently the SD-mini card flew out of your pocket when you went to answer it. There were various failsafes (wikipedia mentions one triggering accidentally after launch: http://en.wikipedia.org/wiki/Voyager_2#Launch_difficulties http://en.wikipedia.org/wiki/Voyager_2#Launch_difficulties ) but keeping around a few copies of everything would probably have been a bit expensive.
- abecedarius 16y agoFurthermore, JPL uses rad-hardened electronics that's far behind the ordinary earthbound stuff of the time.
- hugh3 16y agoAnd besides, it's run just fine for 33 years, so the original design obviously wasn't too badly flawed.
- bkudria 16y agoWhat if the system to guard against this itself got a flipped bit? What if the malfunction caused it to think bits in "normal" memory were flipped when they weren't, really?
- derefr 16y agohttp://en.wikipedia.org/wiki/Fault-tolerant_system#Fault-tolerance_by_replication http://en.wikipedia.org/wiki/Fault-tolerant_system#Fault-tol...
- mturmon 16y agoQuite true. One standard solution is TMR: http://en.wikipedia.org/wiki/Triple_modular_redundancy http://en.wikipedia.org/wiki/Triple_modular_redundancy I doubt that Voyager used TMR, they probably used the best rad-hardened hardware they could build at the time (within power and weight constraints).