was interrupted - so if you get an interruption between the instruction
that clears the Q bit and the RFI that sets it again you don't know
where exactly it happened. If you're lucky the IAOQ will point to the
-instrucion that cleared the Q bit, if you're not it points anywhere
+instruction that cleared the Q bit, if you're not it points anywhere
at all. Usually Q bit problems will show themselves in unexplainable
system hangs or running off the end of physical memory.