Information about basic complex instruction set computer

1. G. H. RAISONI COLLEGE OF ENGINEERING
AND
MANAGEMENT, WAGHOLI, PUNE
Present by:
Venkatesh pensalwar (SCOB20)
Omkar sawant (SCOB24)
Guided By: Prof. Padma Kartik
Subject: CAO
Topic :complexinstructionsetcomputer

2. INDEX
• What is CISC
• Architecture
• Typical x86 design
• Characteristics
• Addressing modes
• The Performance Equation
• CISC pros and cons
• Recent Developments & Future Scope
• Resources
• end

3. WHAT IS CISC?
• Definition: Pronounced "sisk" and standing for Complex Instruction Set
Computer, is a Microprocessor Architecture that aims at achieving complex
operations with single instructions and favors the richness of the
instruction set (typically as many as 200 unique instructions) over the
speed with which individual instructions are executed.

4. ARCHITECTUR
E
A TYPICAL X86
ARCHITECTUR
E

5. CHARACTERISTICS
o CISC are Mostly Von Neumann Architecture (There are few exceptions)
o Same bus for program memory, data memory, I/O, registers, etc
o Generally Micro-coded ,Variable length instructions
o Segmentation is possible with Segment Register s like DS, ES and an
offset which can be common to all segments.
o Many powerful instructions are supported, making the assembly
language programmer’s job much easier.
o Physical Memory Extension Possible

6. ADDRESSING MODES
o Register Addressing Mode
o Memory Addressing Modes
o Displacement Only Addressing Mode
o Register Indirect Addressing Modes
o Indexed Addressing Modes
o Based Indexed Addressing Modes
o Based Indexed Plus Displacement Addressing

7. THE PERFORMANCE EQUATION
The following equation is commonly used for expressing a
computer's performance ability:
1 2
The CISC approach
• minimizes the number of instructions per program (2)
• sacrificing the number of cycles per instruction. (1)

8. CISC PROS & CONS
The advantages of CISC
• Microprogramming is as easy as assembly language to implement, and much less
expensive than hardwiring a control unit.
• As each instruction became more capable, fewer instructions could be used to implement a
given task. This made more efficient use of the relatively slow main memory.
The disadvantages of CISC
• Earlier generations of a processor family generally were contained as a subset in every new
version --- so instruction set & chip hardware become more complex with each generation
of computers.
• individual instructions could be of almost any length---this means that different
instructions will take different amounts of clock time to execute, slowing down the overall
performance of the machine.

9. RECENT DEVELOPMENTS & FUTURE SCOPE
EPIC :
 The biggest threat for CISC and RISC might not be each other, but a new technology called EPIC.
 EPIC stands for Explicitly Parallel Instruction Computing. EPIC can do many instruction executions
in parallel to one another.
 EPIC is a created by Intel and is in a way a combination of both CISC and RISC. This will in theory
allow the processing of Windows-based as well as UNIX-based applications by the same CPU.
 Intel is working on it under code-name Merced. Microsoft is already developing their Win64
standard for it. Like the name says, Merced will be a 64-bit chip.

10. RESOURCES
o http://en.wikipedia.org/wiki/Complex_instruction_set_computer
o http://en.wikipedia.org/wiki/X86

11. Thank you