Updated February 28, 2023
Introduction to Machine Cycle
For the central processing unit (CPU) the machine cycle is considered a list of steps to execute the machine instruction in the computer processor. The machine cycle is considered a list of steps that are required for executing the instruction is received. The machine cycle includes four process cycle which is required for executing the machine instruction. The four process includes reading of instruction, interpretation of machine language, execution of code and storing the result. The processor performs all these four processes in repetition in a sequential manner so that instruction can be executed.
What is Machine Cycle?
Machine cycle is also known as the processor cycle. The Central processing unit (CPU) is the main component for the execution of the machine cycle as it is the main component of the computer system. The main components of the machine cycle are the central processing unit and memory unit. The machine cycle is considered a sequence of four different processes that run in a repetitive manner for the execution of an instruction. The four processes include are, a) fetch b) decode c) execute d) store. In the first process fetch, the control unit asks in main memory for the first instruction for executing which is store in the memory as some specific address which can be easily identified by a program counter (control unit). After getting the instruction the next step is to decode the incoming instruction. The CPU contains the control unit which is used for decoding the instruction in the instruction register. The register is the small component of memory that perform the operations and speed up the processing of the operation. The registers store the instruction which is fetched from the main memory of CPU. The decoding of instruction includes the breaking of the operand field in small components on the basis of instructions opcode. The opcode is part of machine language instructions which gives information about what operation needs to be performed on the instruction. After that, the instruction is executed by the computer processor. The program counter is used for tracking the instruction sequence and track the instruction address as the instruction is executed and the next instruction in the queue for the execution. As the execution of an instruction is completed the output is stored in the memory for later use so that if there is a requirement then the result can be fetched easily.
Steps involved in Machine Cycle
The four steps are briefly discussed in the below section:
1. Fetch Process
In this process, the program counter value fetched which gives the address of the instruction which needed to be executed by the CPU. The instruction is fetched from memory that needs to be executed by the processor. The computer’s main memory stores all the instruction which needs to be executed by the processor. The control unit is the component that is responsible for fetching the instruction from the memory. All instructions are stored at some address location in main memory which can be tracked using the component named as instruction counter.
2. Decode Process
In this process, the fetched instruction is decoded for the execution of an instruction. The decoding process uses the instruction register contents to decode the type of operation which needs to be applied to instruction and inform ALU (Arithmetic logic unit) so that it can be executed for the decoded operand. In the CPU architecture, the control unit takes responsibility for decoding and translating the instruction. After decoding and translating instruction the signals are sent to ALU for the execution of the decoded instruction.
3. Execute Process
In this process, the decoded instruction is finally executed by the computer processor. The CPU is responsible to execute the instruction on the input data (operand). For the computer instruction, there are majorly two components which are operation code (OP code) and operand. The Arithmetic logic unit (ALU) is the component that executes the instruction as per the OP code on the operand which is the input data. For different operation the value of OP code is different. And according to the OP code, the ALU performs the operation on instruction and then the instruction is executed by the processor.
4. Store Process
In this process, the execution result is stored in memory. Once the Arithmetic logical unit operates on data, the result of the operation and processed data is sent to the main memory for the restoration of the result. The memory (RAM) is the main component in this process as the result is stored for later use. For displaying the output on the screen the result is fetched from the main memory or can be used for some other operation as per the requirement. And the stored data is deleted after the use and the whole process is again repeated for the next instruction. All these processes are critical to the processor as the processing speed and the performance of the processor is dependent on these four processes.
Why we Need Machine Cycle?
The machine cycle is required to tell the complete flow of instruction execution so that the internal of the instruction execution can be better understand and if there is any requirement it can be further improved. The machine cycle is the sequential steps for the execution of the instruction and if it is mot there the instructions will not be able to execute properly which can give wrong results. The machine cycle is required for the execution of machine instructions by the processor.
Importance of Machine Cycle
The machine cycle is important for the execution of machine instruction by the computer processor as the device performance is based on the machine cycle. If the instruction is not performed properly the performance can be degraded by the processor. The processing speed and the performance of the device are calculated by the number of instructions that it can execute in the given time span.
Conclusion
The machine cycle has four processes i.e. fetch process, decode process, execute process and store process. All these processes are necessary for the instruction execution by the processor. By the machine cycle, the performance of the processor can be calculated and the device can be selected.
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