cpu architecture performance and embedded systems

The purpose of the CPU is to fetch, decode and execute instructions.

True. The CPU is the brain of the computer and its job is to take an input, process data and produce an output.

The fetch-execute cycle is the cycle that the central processing unit (CPU) runs through billions of times per second to make a computer work.

During the fetch stage of the cycle, the next instruction or data must be fetched from the computer's memory (RAM).

During the decode stage of the cycle, the CPU needs to work out what is required from the instruction.

During the execute stage, the CPU will carry out the instruction that was fetched, such as performing a calculation or storing a result in memory.

The three key stages are: fetch, decode, execute.

An input is clicking a button on the gamepad (or any user input to the computer).

A process is the CPU inside the system following a set of instructions to carry out a task based on the input.

An output is the result produced by the computer, such as the player moving on screen.

The four key components of the CPU are:

The Arithmetic Logic Unit (ALU) performs arithmetic operations and logical decisions.

The Control Unit (CU) coordinates how data moves around the CPU by sending signals to control the flow of data, and it decodes the instructions fetched from memory.

Cache is very small, very fast memory located in the CPU which is used to provide quick access to frequently used instructions and data.

The purpose of Cache is to prevent the CPU from having to repeatedly fetch frequently used instructions from RAM, speeding up performance.

Registers are extremely small, extremely fast memory located in the CPU, where each register has its own specific purpose.

True. The more cache there is, the more frequently used instructions or data can be stored, resulting in fewer fetch cycles from RAM.

The Arithmetic Logic Unit (ALU) performs logical decisions like "IF X > 5 THEN ...".

The Control Unit (CU) decodes the instructions fetched from memory.

Cache has a significantly faster read/write speed than RAM.

The Von Neumann architecture is a design of the CPU proposed by John Von Neumann in the 1940s, which outlines how the computer memory, input/output devices and processor all work together.

The four main registers are:

The Program Counter (PC) holds the memory address of the next instructions to be executed.

The Program Counter increments by 1 as the fetch-decode-execute cycle runs.

The Memory Address Register (MAR) holds the memory address of where data or instructions are to be fetched from.

The Memory Data Register (MDR) stores the data or instruction which has been fetched from memory.

The Accumulator (ACC) stores the results of any calculations that have taken place in the Arithmetic Logic Unit (ALU).

False. The Von Neumann Architecture consists of 4 main registers: Program Counter, Memory Address Register, Memory Data Register, and Accumulator.

The Program Counter (PC) holds the memory address of the next instructions to be executed.

The Memory Data Register (MDR) stores the data or instruction which has been fetched from memory.

The three common characteristics are:

Clock speed is measured in Hertz (Hz) and measures the number of fetch-decode-execute cycles that can take place in 1 second.

True. Modern computers have a clock speed in Gigahertz (GHz), meaning billions of cycles per second.

The faster the Clock Speed, the more instructions can be fetched and executed per second.

A Clock Speed of 3.5GHz means it can perform up to 3.5 billion instructions per second.

Cache is used as temporary storage to provide quick access to frequently used instructions and data.

The larger the Cache Size, the more frequently used instructions or data can be stored, resulting in fewer fetch cycles from RAM and improved performance.

Each core works like its own CPU, so multiple cores allow multiple processing units to fetch, decode and execute instructions simultaneously.

False. A dual-core CPU (2 cores) running at 3.6GHz can perform 2 x 3.6 billion instructions = 7.2 billion instructions per second. A quad-core CPU (4 cores) running at 2.5GHz can perform 4 x 2.5 billion instructions = 10 billion instructions per second.

For a dual-core processor, "dual-core" means there are two cores (processing units) that can fetch, decode and execute instructions.

An embedded system is a computer system with a single function, inside a larger mechanical unit.

Examples of embedded systems include:

The three key properties of an embedded system are:

False. A laptop is not an example of an embedded system. A laptop is an example of a general-purpose computer.

They have a single dedicated function rather than being general-purpose computers.

False. While a fridge has a single main function, it does not contain a CPU, so it is not considered an embedded system.

No. Mobile phones are general-purpose computing devices, not single-function embedded systems.