The control unit is one component of the CPU.
Give two roles of the control unit during the fetch-decode-execute cycle.
Mark scheme
Award one mark for any of the following up to a maximum of two marks:
- Decodes the instruction / works out what the instruction is (1)
- Sends control signals to the other components (of the CPU) (1)
- Coordinates/controls the activities of the CPU (1)
- Directs the timing of the other components / controls when each component acts (1)
Do not accept carrying out arithmetic or logical operations, as this is the role of the ALU.
Do not accept holding/storing the data or instructions, as this is the role of the registers/main memory.
Example answers and how they were marked
It decodes each instruction and sends control signals to the other components to tell them what to do.
Why: Decodes the instruction (1) and sends control signals to the other components (1).
It decodes the instructions and carries out the calculations.
Why: Decoding the instruction (1); the calculations are carried out by the ALU, so the second part earns nothing.
It stores the data that the CPU is working on.
Why: Storing data is the role of the registers/main memory, not the control unit, so no point is creditworthy.