How large can a memory be? It may seem that memory size is only an economic
issue — more memory simply costs more money. However, size turns out be an essential
aspect of memory architecture because overall memory size is inherently linked to
other choices such as the addressing scheme.
The most significant limitation on size arises because a processor imposes a fixed
bound on the size of an address that can be generated. Typically, the processor limits
an address to be the same size as an integer. For example, a system that uses thirty-two
bit integers typically uses thirty-two bit addresses. As Chapter 3 points out, a string of
k bits can represent 2k values. Thus, a thirty-two bit value can represent: