9. Internal Components

Question 1

Fetch-Execute Cycle

Answer 1

The process of how a computer processes information and instructions.
Consists of 3 parts: Fetch, Decode, Execute.

Question 2

Fetch

Answer 2

• > Contents of PC get copied onto MAR
• > Address bus is used to transfer this address onto main memory
• > Contents of addressed memory location loaded into the MBR
• > Transfers data through the data bus
• > Increments PC by one
• > Transfers contents of MBR to CIR

Question 3

Decode

Answer 3

• > Instruction to be decoded is held in CIR
• > The CU decodes the instruction
• > The instruction is split into opcode and operand

Question 4

Execute

Answer 4

If necessary, data is fetched

• > Opcode identifies the type of instruction it is
• > Operand is the data to be acted on.
• > Execute instruction by relevant part of processor
• > Result is stored in the accumulator
• > Status register is updated

Question 5

PC

Answer 5

Program Counter

It is a register that indicates where the computer is in its program’s sequence.

Question 6

MAR

Answer 6

Memory Address Register

This register holds onto memory location of data that needs to be accessed.

Question 7

Address Bus

Answer 7

Unidirectional

Adresses come out of the CPU and into other components.

Question 8

MBR

Answer 8

Memory Buffer Register

It acts as a buffer allowing the processor and memory units to act independently without being affected by minor differences in operation. It’s contents will then be copied onto the CIR to be decoded.