There is a simple solution to that: provide a *Queue* of Q-Table entries.
+Below is what a 6600 Q-Table looks like (image courtesy of Mitch Alsup).
+In the original 6600 it is a binary table with a unary decoder on the
+left and a pair of unary encoders on the right.
+
+{{6600_q_table.png}}
+
Now we have exactly the information needed to "roll back", should an
exception occur. Like many augmentations and enhancements to the 6600
Scoreboard system, it's kind-of obvious in retrospect. However the *real*