1.1.1 Systems Architecture

Today's Knowledge

 - The Purpose of the CPU

- Common CPU components and their functions

- Von Neumann Architecture

What you need to know:

1.1.1 Fetch Decode & Execute Cycle.

The fetch-decode-execute cycle describes the basic operation

of modern computers.

 

Fetch

-        Instructions are loaded into the RAM (main memory)

-        Each instruction is then fetched from main memory (in order)

 

Decode

-        The instruction is then decoded (works out what it needs to do)

 

Execute

-        The decoded instruction is then executed (carried out)

-        Examples of an instruction can be… performing a calculation. Storing information back into RAM 

Related topic:

Clock speed:  3Ghz CPU = 3 billion (FDE) cycles per second

Common CPU components and their function & Von Neumann Architecture:

ALU (Arithmetic Logic Unit)

Performs calculations and logical decisions.

Manages: Arithmetic and logical operations, calculations and comparisons.

 

CU (Control Unit)

Sends signals to other components controlling how data moves around the CPU.

Manages: The instructions            Controls:  The other components

 

Cache

Stores and provides fast access to frequently used instructions and data.

 

Registers (high speed memory that helps the control of data around the CPU)

Program Counter (PC): Stores the address of the next instruction to be run.

Memory Address Register (MAR): Stores the address of where data is fetched from.

Memory Data Register (MDR): Stores the data that is fetched from main memory.

Accumulator (Acc): Stores the results of the calculation.

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