RISC vs CISC

The major difference is that RISC has fewer number of instructions and each of them performs simpler function, has simpler format, and most instructions have the same number of clock cycles, so we can apply pipeline technique to improve performance. On the other hand, CISC processors have a large amount of different, complex instructions, and each of them may require various number of clock cycles and contain various number of bits. RISC processor has better performance, but CISC processor can has code which has much less lines than RISC processor. Moreover, CISC typically requires more hardware resource to support its powerful instructions, therefore also has higher power consumption. For example, CISC may has a dedicated hardware for multiplication, while RISC may combine shift and add instruction to achieve multiplication.