1.
CISC vs RISC
by : Kaushik Patra
(kpatra@gmail.com)
a beginner’s reference

2.
Agenda
A quick introduction
Instruction Set Architecture
(ISA)
ISA classification
CISC philosophy
RISC philosophy
Conclusion

3.
Introduction

4.
ISA
Instruction Set Architecture.
An agreement between hardware
and human for making interaction.
Example : ADD R1, R2, R3
Can be represented as :
00101111100001111001010101010101
10111010100011110101001011011010

5.
ISA Classification
Two major schools of ISA
CISC
Complex Instruction Set Computer
RISC
Reduced Instruction Set Computer

6.
CISC Philosophy
Reduce amount of storage used and
accessed - reduce load/store.
Give support for compatibility.
Make compiler’s job easier.
Support complex assembly level
programming.

7.
RISC Philosophy
Execute one instruction per
clock.
Keep all instructions of same
size.
Allow only load / store
instruction to access the memory.
Give support for high level
languages (like C, C++, Java).

8.
Conclusion
CISC -> RISC : A paradigm shift
Assembly -> C / C++ / JAVA
Much more design simplicity with
RISC.
Ensures better pipelining.
Memory is cheaper nowadays
So, go for RISC style design.