Quote: (from a while back in this thread)
A bigger software issue these days is 'supposed' redundancy that actually isn't. Like the Boeing 787 that has 4 generators fail at the same time, because their software has a flaw.
Let's put this "flaw" in perspective.
1. It has NEVER happened operationally, only in the test lab.
2. It will ONLY happen if the system runs continuously for 248 days.
3. The "workaround" to prevent this from happening is to shut down the system before 248 days have elapsed.
4. No one anywhere has ever or will ever run a 787 continuously for 248 days. Conclusion: not a problem in any meaningful sense, but Boeing still notified its users of this "flaw", which was eliminated in the next software revision.
Ah! The old (2^31) - 1 hundredths of a second signed 32 bit integer problem.
I first saw this in about 1997 in production kit that was expected to work for years without a reboot.
In that case the code came from some old Unix(y) stuff that was re-purposed. The thing simply stopped working after 248 days until turned off and on again.
248 days = 2,142,720,000 hundredths of a second
(2^31) -1 = 2,147,483,647