vovachan and xetroV,
You have me scratching my head....
I'm an ancient from the Concord era, when the integrated circuits were still so huge, that a single cosmic ray, neutron or alpha particle couldn't really upset the electronics.
But components could fail. So (to stay with flight control computers, analog in those far-off days), each computer had two virtually identical channels, dubbed "command" and "monitor", and comparators all down the chain (and those were duplicated too) checked that "C" and "M" told exactly the same story. If they didn't ... "boing" and the computer disengaged. Then, on the other side of the aircraft, a second computer, until then in standby, would take over.
Checks for passive failures (like a comparator failing "healthy") were dealt with by preflight BITE (built-in tests), and some of those tests were repreated just before an autoland, reducing the "period at risk" to only minutes.
I wasn't directly involved in the earliest DAFS, but by looking over their shoulder, I saw most of the same principles were applied.
So what's been going on since?
Even with ROMs, RAMs and everything else today being far far smaller, I still would think the probabilty of two particles hitting the same spot in two "halves" of a system provoking an identical spike, that then would be missed by the comparators, would be infinitesimal.
So has there been a fundamental change in architecture?
And wouldn't that kind of change be equally bad at catching component and software failures as "cosmic ray" events?
I can see the line of thinking of the ATSB... I would have be tempted too, if everything afterwards worked perfectly, and there was no way of reproducing the fault. But there still seems to be something wrong with that reasoning....
CJ