The Von Neumann Computer Architecture — Explained
The Von Neumann Architecture is one of the most important aspect of computing, as it shows the components of the computer system and how they work in tandem with each other. It is a fundamental concept you need to grasp the idea of, if you plan on studying computing full-time. In this article, I shall show you everything you need to know about the Von Neumann Architecture.
The main components of a Computer Architecture
- Input/Output Devices
- The Memory Unit
- The CPU
- The Buses (Address, Data and Control)
Now, I will explain each component further so you can fully understand what they are.
Input/Output Devices
Input Devices — devices that sends information into the computer, eg: keyboard, mouse, microphone, touchscreen, etc.
Output devices — devices that sends information out of the computer, eg: monitor, speaker, printer, etc.
The Memory Unit
The memory unit is usually primary memory. Inside the primary memory consists of the Random Access Memory (RAM) and the Read-Only Memory (ROM).
The RAM is used to store data that is currently in use. This is when the computer is on, data that is used is added into the RAM. However, since this is a volatile (temporary) memory, once the computer is off, all the data that was in the RAM is lost.
The ROM is used to store permanent data and basic instructions such as the BIOS/start-up instructions for your computer. This is different to RAM as the memory is non-volatile (permanent), therefore even when the computer is off, all thse data is stored and retained in the ROM.
Difference between RAM and ROM
- RAM is volatile, while ROM is non-volatile.
- RAM has a read-and-write operation (meaning a computer program is able to read information from a file and add new info, or edit existing information in a computer program), while ROM only has read operations.
- RAM’s storage capacity is larger than ROM.
- ROm stores the start-up instructions or the BIOS, RAM stores the data currently in use when the computer is on.
The Central Processing Unit (CPU)
Definition — “a hardware component that is able to perform arithmetic, logical or input/output instructions”.
The CPU can be thought like the “brain” of the computer system. Even though CPUs have developed to be more advanced, iit can only process data when given instructions, it can’t think or act by itself.
The CPU consists of two main registers:
- Memory Address Register (MAR)
- Memory Data Register (MDR)
A register is a high speed, temporary storage area
The MAR holds the address of the data that is to be used by the ALU, so that it can fetch and process the instruction accordingly. The MAR may also hold the address of where processed data will need to be stored; or to put it into other terms: the location of the processed data in the primary memory.
The MDR holds the contents that was found at the address held in the MAR, or data that is to be transferred to the primary memory.
The Buses
A bus is a high speed internal connection. They are used to send signals around the computer system. Think of it as the ‘wires’ of the computer architecture. There are three types of buses: address, data and control buses.
Address buses carries the address of the instruction from the CPU (also known as the processor) to other parts of the computer system such as the primary memory.
Data buses carry data between the processor and other components.
Control buses carry control signals from the processor to other components of the computer system.
