CISC and RISC

By Raul Bernardino

Introduction

The computer architects are designing central processing units (CPU) with a comprehensive structure of commands in which can be executed. They are divided the computer processors instruction in two major groups of philosophy of the CPU.

The first group of designers is focusing on minimum set of machine instructions which can be executed and it calls RISC. The RISC is an abbreviation of Reduced Instruction Set Computer (RISC). Because of the simplicity in the instruction, it becomes a common statement or argument that RISC architecture is faster and efficient.

The second group of designer is focusing on the complexity of processor instruction s in which to be executed and it calls CISC. The

CISC is an abbreviation of Complex Instruction Set Computer (CISC). Because of the complexity of instruction architecture, it is easier to program s processors and it would be a single instruction to accomplish multi tasks rather than multi-instruction like in the RISC.

The advantages of RISC:

• The new tested micro-processor will be developing processor more faster
• System developer can be easily developing a code with smaller instruction set
• More freedom for system developer to use the space

One of the characteristics of the RISC is simplification of instructions, same length of instructions, and one machine-cycle instruction.

Pros and Cons of RISC

The implementation a simple instruction in system design has more advantage. Since, it is simplify the instruction, the speed will be high compare to CISC in same clock rate; the simplicity of instruction in RISC processor also makes smaller chips and has more space.

The design of the RISC processors is quicker than the CISC processors design. The CISC and RISC are having processors terms. The terms are becoming meaningless of both RISC and CISC evolution. It has been implementing in the processor of 486 in the Intel, AMD, Cytrix, and IBM companies.

Pros and Cons of CISC

Advantages: Initial development, the instructions of processor used a technology to maximize a performance of computer.

• Using micro-programming of assembly which cheap compare to hard wiring as unit control
• The micro-coding instructions to allowed designers make a processor upwardly compatibility
• Efficient by using the slowness of main memory
• The compiler has not been a complicated

Disadvantages of CISC as follows:

• The processor families were contained as a subset in every new instruction
• Many instructions could be stored in memory with which is not wasting space
• Typical instructions set create condition codes that has side effect of the instruction

Beside these two groups of philosophies above, they are also divided into three major operations which are data transfer, arithmetic/logic, and data control.

Bibliography:

• Reduced instruction set computing[Internet].Available from: http://en.wikipedia.org/wiki/Reduced_instruction_set_computing (Accessed: 8 February 2013)
• CISC (Complex Instruction Set Computer) [Internet]. Available from: http://www.laynetworks.com/CISC.htm (Accessed: 8 February 2013)
• J. Glenn Brookshear, (2009) Computer science: An Overview and Machines Language. 10th Edition, Boston: Pearson Addison Wesley, Ch 2, Sec 2.2, P.103-104