Write short notes on RISC and CISC
Answers
A computer with a large number of instructions is classified as a complex instruction set computer. A computer uses few instructions with simple constructs so they can be executed at a much faster rate within the CPU without having to use the memory often. This type of computer is classified as Reduced Instruction set computer.
The major characteristics of CISC architecture are:
1) A large number of instructions typically from 100 to 250 instructions.
2) Same instructions performed specialized tasks and are used unfrequently.
3) Large variety of addressing modes.
4) Variable length instruction formats.
5) Instructions that manipulates operands in memory.
RISC Characteristics:
In Reduced Instruction set Computers, CPU is capable of executing only a very limited set of instructions. One advantage of RISC that they can execute their instructions very fast because the instructions are very simple and RISC chip requires fewer transistors, which makes them cheaper to design and produce.
The main characteristics of RISC:
i) Reduced Instruction set.
ii) Less complex, simple instructions.
iii) Hardwired control unit
iv) Few addressing modes.
v) Instruction pipelining.