ABSTRACT
BASIC PROCESSOR ARCHITECTURE Every general purpose processor conceived since the Electronic Discrete Variable Automatic Calculator (EDVAC) and Electronic Delay Storage Automatic Calculator (EDSAC) of the 1950s operates on the principle of the basic fetch-execute cycle. A machine instruction is fetched from program memory, decoded, and then executed. is cycle is driven by a series of clock pulses and repeats ad in¢nitum, usually until the processor is powered down. Memory is usually organized as a series of bytes or words and is accessed by address. e processor keeps track of the address of the next instruction to be fetched in a register called the program counter (PC) or instruction pointer. As the instruction is fetched, the PC is updated to point to the next instruction; usually this is done by incrementing it by a ¢xed amount. Some processors have variable length instructions making the update of the PC a little more complicated. Figure 1.1 illustrates the fundamental components of a typical processor and program memory.
