Embedded Files
Learners should have studied the following:
- MAR (Memory Address Register)
- MDR (Memory Data Register)
- Program Counter
- Accumulator
The Purpose of the Central Processing Unit (CPU)
The Purpose of the Central Processing Unit (CPU)
The CPU (Central Processing Unit) is the part of a computer system that is commonly referred to as the "brains" of a computer. The CPU is also known as the processor or microprocessor.
The CPU is responsible for executing a sequence of stored instructions called a program. This program will take inputs from an input device, process the input in some way and output the results to an output device.
CPUs aren’t only found in desktop or laptop computers, many electronic devices now rely on them for their operation. Mobile phones, DVD players and washing machines are examples of equipment that have a CPU.
John Von Neumann
John Von Neumann
John Von Neumann was a mathematician and physicist who studied how to design a computer and came us with a system that is used almost universally in modern computer systems. His designs include the concept of having a program that is stored and is executed when the computer runs. The program is stored in memory (often loaded from a hard drive), and the instructions are fetched, decoded and executed, and a single control unit controls the flow of program instructions and data around the system.
You will need to know how the Von Neumann architecture works in a CPU, and the names of the main components that it uses.
Instructions are firstly fetched from memory, and then decoded in the control unit. Once they have been decoded, they will be executed. You should memorise the phrase "The purpose of the CPU is to fetch, decode and execute instructions" as this question will appear frequently on exam papers.
John Von Neumann (1903-1957) was an American mathematician and physicist who came up with the concept of self replicating organisms (a precursor to the discovery of DNA), worked on the design of the first nucleur bomb, and drew up the blueprint for the Von Neumann architecture which is used on almost all modern computer systems.
The Main Parts of the Von Neumann Architecture.
The Main Parts of the Von Neumann Architecture.
The Von Neumann architecture divides the internal parts of the CPU into specific sections.
For your exam, you will need to be able to label a diagram and explain what each section does.
Use this carousel to investigate the different sections.
You can click on the carousel to pause it, and use the left and right arrows to move between each section.
Once you have read and understood each one, go through the Von Neumann Animation slideshow below, which explain in detail how a CPU fetches, decodes, and executes a simple program.
Cache
Cache
Cache memory is one of the key components of the CPU. Inside the CPU chip is an area of super fast memory not unlike RAM.
The Cache memory can rapidly load data and code from the RAM and deliver them along the internal buses at a much faster rate compared with the external address bus and data bus. Using a CPU with a larger amount of RAM will make the whole computer system run significantly more quickly.
In this picture you can actually see the bus lines on the motherboard which run between the CPU, the RAM and other sections on the system.
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