Dear Professor Patt,

     On the answer for question 2 part A on Old Exam 1 the
     answer given was four for "What is the address space?"
     My study group and I wanted to know why that is the answer
     and not three. Since the 2^2 by memory in the book on page 69
     has an address space of four should the one in the old exam
     have an address space of 3? Or is address space calculated
     only by how many address lines are included


     and not by how many spaces are shown on the diagram?

Yes, there are three locations implemented, but address space refers (as you pointed out above) to the number of locations that "could be" implemented, that is, to the number of distinct addresses there are, which is four (2^2).

For example, if you have 30 bits of address, you have an address space of 1 billion locations (2^30), even though your personal computer may only have 256 million locations actually implemented.

Yale Patt

     Thank You,
     << name withheld to protect the caring classmate >>