Controls all the operations in the CPU Transfers data to registers Directs data to ALU for calculation

Ensures correct paths for data transfer Synchronisation with the system clock

Click on image to go to the Fetch-Execute Cycle

Performs calculations

Tests logic functions

Determines relative relationships between values

Click on image to go to the Fetch-Execute Cycle

Storage register Stores the next instruction to be executed

Accumulator Stores the latest results from a calculation

Address register Stores memory address locations

Instruction register Stores instructions to be processed Click on image

to go to the Fetch-Execute Cycle

The system clock is an accurate, very fast electronic timer.

The faster the system clock the more instructions per second are executed.

Buses are pathways – separate wires / metallic strips which transport signals (data).

http://www.webopedia.com/TERM/b/bus.html

Fetch:•The instruction is fetched from memory.•Instructions are stored in registers.

Decode•the opcode is decoded by the CU so the instruction can be executed.

Execute•The instruction is executed, usually using the ALU.

Store•The result of the instruction is stored.

Note: this is a simplified explanation (what is required knowledge for the Preliminary course – see link for further detail).

http://en.wikipedia.org/wiki/Instruction_cycle

Decode:• The typical instruction is divided into two parts: the

Opcode and the Operand• The opcode is the instruction.• The operand is the data on which the instruction needs

to be performed.

In the simplified example below:

Add 10

• Add would be the instruction (opcode).• 10 would be the data (operand).

More input / output devices Increased processing speed Larger memory (both primary and

secondary) which is better for working with sound and graphics