Processor Components – The CPU
The CPU takes instructions from the memory and decodes them and then executes them millions of
times a second, it has multiple components which allows it to do this function
Control Unit:
Controls and coordinates CPU activities breaks instructions down into steps like getting addresses
and storing data and then executes these, then stores this data in memory/registers
Buses: overview
- A bus is a set of parallel wires connecting two or more components of the computer (comes
in sets of 8, 16, 32, or 64)
- There are 3 buses that connects the processor to the main memory: the Address bus, the
Data bus, and the Control bus (these 3 are all known as the System bus)
- The Address bus allows the CPU to request a particular part of the memory (the address is
sent along here)
- The Data bus allows the CPU to return the requested data from the memory back to the CPU
- The Control bus allows control signals to be sent
- Data and control signals along the two buses can be sent in both directions whereas the data
being sent along the address bus can only go one direction
Buses: The Control Bus
- As the data and address buses are shared by the computer, the control bus must provide
control to that access and share of data is conflicted by the various components
- The control bus transmits commands, timing and specific status information between the
system components
- Examples of control lines:
1. Clock: used to synchronise operations
2. Memory read: data found in the memory location is sent back to the CPU
3. Memory write: data on data bus is written to memory locations
4. Bus request / bus grant: device requests to use data bus and the CPU grants it
Buses: The Data Bus
- Provides a bi-directional line for moving data between the CPU and components
- 8, 16, 32, or 64 lines
Buses: The Address Bus
- The main memory is divided into Units called Words, each Word is a fixed group of digits (16,
32, or 64 bit)
- These units are handled by the processor (different processors have different word sizes)
- Use of these Words gives each unit its own specific memory address
- The address bus transmits the memory location of the Words that want to be used by the
CPU
- The Data bus then transmits the result of this operation back to the word and it is written
The CPU takes instructions from the memory and decodes them and then executes them millions of
times a second, it has multiple components which allows it to do this function
Control Unit:
Controls and coordinates CPU activities breaks instructions down into steps like getting addresses
and storing data and then executes these, then stores this data in memory/registers
Buses: overview
- A bus is a set of parallel wires connecting two or more components of the computer (comes
in sets of 8, 16, 32, or 64)
- There are 3 buses that connects the processor to the main memory: the Address bus, the
Data bus, and the Control bus (these 3 are all known as the System bus)
- The Address bus allows the CPU to request a particular part of the memory (the address is
sent along here)
- The Data bus allows the CPU to return the requested data from the memory back to the CPU
- The Control bus allows control signals to be sent
- Data and control signals along the two buses can be sent in both directions whereas the data
being sent along the address bus can only go one direction
Buses: The Control Bus
- As the data and address buses are shared by the computer, the control bus must provide
control to that access and share of data is conflicted by the various components
- The control bus transmits commands, timing and specific status information between the
system components
- Examples of control lines:
1. Clock: used to synchronise operations
2. Memory read: data found in the memory location is sent back to the CPU
3. Memory write: data on data bus is written to memory locations
4. Bus request / bus grant: device requests to use data bus and the CPU grants it
Buses: The Data Bus
- Provides a bi-directional line for moving data between the CPU and components
- 8, 16, 32, or 64 lines
Buses: The Address Bus
- The main memory is divided into Units called Words, each Word is a fixed group of digits (16,
32, or 64 bit)
- These units are handled by the processor (different processors have different word sizes)
- Use of these Words gives each unit its own specific memory address
- The address bus transmits the memory location of the Words that want to be used by the
CPU
- The Data bus then transmits the result of this operation back to the word and it is written
