RISC/CISC architecture
Comparison between RISC and CISC:
| RISC | CISC |
Acronym | It stands for ‘Reduced Instruction Set Computer’. | It stands for ‘Complex Instruction Set Computer’. |
Definition | The RISC processors have a smaller set of instructions with few addressing nodes. | The CISC processors have a larger set of instructions with many addressing nodes. |
Memory unit | It has no memory unit and uses a separate hardware to implement instructions. | It has a memory unit to implement complex instructions. |
Program | It has a hard-wired unit of programming. | It has a micro-programming unit. |
Design | It is a complex complier design. | It is an easy complier design. |
Calculations | The calculations are faster and precise. | The calculations are slow and precise. |
Decoding | Decoding of instructions is simple. | Decoding of instructions is complex. |
Time | Execution time is very less. | Execution time is very high. |
External memory | It does not require external memory for calculations. | It requires external memory for calculations. |
Pipelining | Pipelining does function correctly. | Pipelining does not function correctly. |
Stalling | Stalling is mostly reduced in processors. | The processors often stall. |
Code expansion | Code expansion can be a problem. | Code expansion is not a problem. |
Disc space | The space is saved. | The space is wasted. |
Applications | Used in high end applications such as video processing, telecommunications and image processing. | Used in low end applications such as security systems, home automations, etc. |
Difference between RISC and CISC
S.No. | RISC | CISC |
1. | Simple instruction set | Complex instruction set |
2. | Consists of Large number of registers. | Less number of registers |
3. | Larger Program | Smaller program |
4. | Simple processor circuitry (small number of transistors) | Complex processor circuitry (more number of transistors) |
5. | More RAM usage | Little Ram usage |
6. | Simple addressing modes | Variety of addressing modes |
7. | Fixed length instructions | Variable length instructions |
8. | Fixed number of clock cycles for executing one instruction | Variable number of clock cycles for each instructions |
