What is the meaning of the subclause of 'goes off the deep end'?

If a real-time program goes off the deep end, the system can become unresponsive.

Solution 1:

This is one of several idioms related to the dangers of deep water. These include:

go off the deep end - lose one's temper, act rashly or get carried away with something
throw someone in at the deep end - put someone in a challenging position without preparation
in deep water - in trouble, in a difficult situation

Your example doesn't quite fit the usual meaning of the idiom. Presumably they mean that if a real-time program becomes overloaded or goes wrong it will make the system unresponsive.

Solution 2:

"Going off the deep end" just means going out of control. Synonyms are "going haywire", "going kablooey", and so on.