Question

(a) The control unit (CU) in the central processing unit (CPU) controls the data flow and operations in the CPU.

Explain the difference between the two methods used for designing the control unit. [6 marks]

(b) Explain the difference between the direct and indirect addressing moods. [4 marks]

(c) Explain how an instruction is fetched in the fetch decode execute cycle. [5 marks]

(d) What is the difference between a 16-bit microprocessor and 32-bit Pentium microprocessors?

Answer 1

Ans (a) :- Control unit tells how to respond to the instructions that are sent to the processor. It generates control signal by fetching instruction from the main memory to the computer register. It converts input information to control signals. It receives control signals from other devices.

Ans (b) :-

Direct Addressing mode :- In direct Addressing actual address of the operand is used. The instruction is direct address if the address part of the operand has the direct address. The memory access is faster.

Indirect addressing mode :- Where the address of the operand is contained in a register pair then that mode is indirect addressing mode. The memory access is slower than direct addressing mode and the address space is large.

Ans (c) :- Executing programs using fetch decode execute cycle is the CPUs main job. Each machine code instruction in a program takes up a slot in main memory and every slot has a memory address. Then address of each instruction is stored by Program Counter and in which path it should be carried out is viewed. Then while executing CPU performs fetch decode execute cycle.

Ans (d) :-

16-bit microprocessor :- Transferring 16-bits of data at a time capable by a 16-bit hardware or software devices meaning they are capable of working with 16-bit binary numbers.

32-bit pentium microprocessor :- Pentium is a brand used in 86 architecture microprocessor where 32-bits of data is transferred at a time.