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The machine cycle is the main activity performed by the microprocessor to execute the program instructions. The Machine cycle in the context of CPU ( Central Processing Unit ) is also alternately referred to as Instruction cycle or CPU cycle Or processor cycle. However, the machine is part of the instruction cycle.
In computer architecture, a machine cycle refers to the basic operational steps that a central processing unit (CPU) performs to execute an instruction. These steps are typically divided into several stages, including fetch, decode, execute, and store.
The CPU is driven by internal clock cycles. It is important to understand the concept of CPU clock cycles since it is closely related to the concept of machine cycle. Depending upon microprocessor design it might take one or more clock cycles to perform one machine cycle.
Let us consider one example of the instruction cycle to understand the difference between the machine cycle and the instruction cycle. The performance of the microprocessor depends upon the CPU architecture, clock speed and the efficiency of process design in terms of number of machine cycles required to execute one part of the instruction cycle.
In the following example, the fetch part of the instruction cycle needs two machine cycles. Whereas, the execute part needs three machine cycles presuming one machine cycle needs one clock cycle.
The instruction cycle is the time taken to execute one instruction. Depending upon the complexity of the program instruction, one instruction generally needs number of machine cycles and one machine cycle might need one or more clock cycles.
In this article, we will discuss in detail what is machine cycle , the difference between instruction cycle and machine cycle , how CPU executes the program instructions and the various steps involved for the completion of one instruction cycle.
