Re: How would Ariane 5 have behaved if overflow checking werenotturned off?

["robin" <robin51@dodo.com.au>]

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Vinzent Hoefler <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de> wrote in message ...
>robin wrote:

>> Vinzent Hoefler <0439279208b62c95f1880bf0f8776eeb@t-domaingrabbing.de> wrote in message ...
>>> Elias Salomão Helou Neto wrote:
>
>>>> Since then I have been wondering. If compiler checking where actually
>>>> turned on, what would have happened?
>
>>> The same, according to the specification.
>
>>>> How could it avoid the disaster?
>
>>> Not at all.
>
>> On the contrary., an error handler would have performed
>> something useful.

>Precisely what? The _only_ reasonable action at that point was to assume
>a hardware error and shutdown the computer. For Ariane 4, that is.

Whether Ariane 4 or 5, it was not reasonable to assume that the
error was hardware.
See my post elsewhere.

>> The crux of the matter is that the data bus would not have been
>> loaded with an error number [which was then treated as guidance data].

>AFAIK this was required in case both systems died. And as we know, they
>did exactly that.

But only if the error was hardware, which it wasn't.

> I'd assume the possibility of two hardware errors at
>the same time were considered remote.

>>> By handling it exactly the way it was supposed to be:
>
>>> Assuming a hardware error and leave control to the redundant subsystem.
>
>> That was the major blunder that they made,
>> namely, treating a programming error as a hardware error.
>> By doing that, they guaranteed failure of the mission.

>Again. In the Ariane 4 it would have been exactly that. A hardware error.

Again, you are making a false assumption.

>There was no freaking way, Ariane 4 could have exceeded the safe range.

recall Murphy, "If anything can go wrong, it will".

>>> Which one, if any, is close to reality?
>
>>> As it has been mentioned here many times before, the software behaved
>>> exactly as specified and it is very unlikely that _any_ error handling
>>> could have avoided the problem
>
>> An error handler would have rescued the mission.

>Only if were not behaving according to the specification. That means if
>it were buggy -

It was buggy.  It didn't handle the overflow.