As noted earlier, the CPU is also called a microprocessor because all of its components—at least all those needed to carry out calculations—are on a single silicon chip (see Chapter 4 for a discussion of how chips are made). We'll begin our overview of the microprocessor with a simple description of its functions. The classical CPU includes a four-sequence operation (see Figure 1.4).
First, instructions and data are fetched from outside the chip (usually this means from DRAM). An example of an instruction is one that contains a simple mathematical operation such as "add." In some cases, the data used by an instruction are included with it; in other instances, the instruction references ...