> From: William Degnan > The IOT step is bombing (?) and loops through the addresses:
This may be a pointless question, but just to clear the ground first: the CPU is otherwise functioning reasonably well? E.g. it's not dropping the 020 bit when reading words from memory? (That would convert the '220' new PC in the vector to '200', and produce exactly the behaviour you are seeing.) If it is otherwise more or less working, so this is specific to IOT trap handling, I agree with Fritz - a KM11 would be a big help. Noel