Week2 SPO600 von Neumann architecture

Hello everyone, welcome back to the second week of SPO600(Software Portability and Optimization) reflection and extra exploration blog! In this blog, I'm going to share some thoughts and dig more about von Neumann architecture.

von Neumann architecture

How it works

The von Neumann architecture is a computer architecture which was described by John von Neumann. The von Neumann model is designed for electronic digital computer with 5 units.

A processing unit which contains an arithmetic logic unit and processor register. The processing unit is used to process calculation and logical operation, then temporarily store them into a register.
A control unit that contains instruction register and program counter. Control unit is used to control and direct the procedure of a program then process the result of processing.

3.Input mechanisms, such as keyboard, mouse.

4.Output mechanisms, such as monitor, printer.

5.Memory which stores data and instructions.

The instruction and data of von Neumann architecture uses a binary system, they are stored in the same register that could be accessed by using an address. The instruction is a composition of opcode and address code. The opcode is used to represent the type of the operation, and the address code is used to represent the location of the operands in the memory. Usually, instructions are stored in order in the memory. For a certain situation, the execution order can be changed according to the operation results or the set conditions. The machine takes the arithmetic logic unit as the center, the data transmission between input and output devices passes the arithmetic logic unit.

Because the arithmetic unit and control unit are closely intertwined in logic and circuit structure. Usually, they are collectively referred as the central processor unit, the input and output devices known as I/O devices, so the modern computers can think to be a composition of three parts: CPU and the main memory can be referred to as the host, I/O devices are usually called external devices.