1.1.1 - Architecture of a CPU

What does the ‘fetch’ in the FDE cycle mean?

Fetch an instruction from main memory

What does the ‘decode' in the FDE cycle mean?

Decode the instruction from main memory

What does the ‘execute’ in the FDE cycle mean?

Carry out the instruction

What is the FDE cycle?

It describes the basic operation that all modern computer systems use

What is the CPU?

Central Processing Unit - where all the data is processed and where the FDE cycle is carried out.

What are the main components of the CPU?

• Arithmetic Logic Unit

• Control Unit

• Cache

• Registers

What are registers?

High speed devices used by the CPU to store small amounts of data used for certain processes

What do registers mainly process?

The addresses of the next instruction to be executed and the results of calculations

What are the five types of registers?

• Program counter

• Memory Address Register

• Memory Data Register

• Current Instruction Register

• Accumulator

What does the program counter do?

It holds the RAM address of the next instruction to be fetched from main memory

What does Memory Address Register do?

Holds the memory address where instructions will be fetched from or data fetched from/stored to

What does the Memory Data Register do?

Holds the current data that has been fetched from memory OR is about to be stored in memory

What does the Current Instruction Register do?

It holds the instruction that is currently being processed - the instruction that is about to get executed

What does the Accumulator do?

It stores the result of the current calculation from ALU, stores input into ALU

What is the purpose of the Control Unit?

To control and monitor the flow of data between the hardware components and the CPU. It also executes the instructions provided by the program

What is the purpose of the Arithmetic Logic Unit?

It handles all of the data processing within the CPU. It performs standard arithmetic (fancy that) operations like subtraction, addition, multiplication and division and also deals with logical comparisons such as ‘is this value greater than this value?’

What is cache?

High speed volatile memory that is built into the processor