Those of you who are studying the old exams in EE 306 should be aware of
important changes from the LC-2 to the LC-3.  Some of the instructions
are encoded differently for the two ISAs, and some of those differences
are subtle.  Rather than list all the differences, let me simply suggest
that while you are welcome to look at the problems on the old exams, the
solutions that are provided may not be correct in terms of the LC-3.

One example is the LD instruction, where bits[8:0] of the instruction are
used differently in the LC-2 and LC-3 to compute the address of the load. 
There are many others. 

Good luck on the second midterm on Wednesday.

Yale Patt