1. G.S. Mandals Maharashtra Institute of
Technology
Instruction Set in VLSI
Sahil Maske : T3434
Vinit Navgire : T3436
Vaibhav Murade : T3464
2. Instuction Set
In Very Large Scale Integration (VLSI) design, an instruction set refers to the set of instructions that a
microprocessor or microcontroller can execute.
The instructions are the basic operations that the processor can perform, such as arithmetic
operations (e.g., addition, subtraction), logical operations (e.g., AND, OR), data movement (e.g., load,
store), and control flow (e.g., branch, jump).
The instruction set architecture (ISA) : defines the machine-level interface between software and
hardware in a computer system. It specifies the format of machine instructions, the addressing
modes available, the register set, and the behavior of each instruction.
3. Types of Instruction Set :
Factors Deciding the Types of Instruction set are
1) Complexity of Instructions
2) Instruction Execution Philosophy
3) Compiler Optimization
4) Power Efficiency
A. Complex Instruction Set Computer (CISC)
B. Reduced Instruction Set Computer (RISC)
C. Very Long Instruction Word (VLIW)
Types
4. Complex Instruction Set Computer (CISC)
CISC stands for Complex Instruction Set Computer. It's an architecture where the CPU executes a large number
of complex instructions , it can perform multiple task in a single instructions .(Adv)
CISC processors often allow memory-to-memory operations, meaning they can directly operate on
data in memory, reducing the need for frequent register transfers.
CISC instructions are often of variable length, which can make instruction fetching and decoding more
complex.
CISC architectures were popular in early computer designs, such as the Intel x86 architecture.
CISC architectures often require more complex hardware to decode and execute a wide range of
instructions, which can lead to higher power consumption and longer instruction execution times.(Dis -
Adv)
5. Reduced Instruction Set Computer (RISC)
RISC stands for Reduced Instruction Set Computer. It's an architecture where the CPU executes
a simplified and reduced set of instructions, these instructions are typically executed in a single
clock cycle.
RISC architectures excel in executing instructions quickly and efficiently, making them suitable
for applications demanding high-speed processing. (Adv)
RISC architectures typically have a larger number of registers available for operations, which
reduces the need for frequent memory accesses.
The simplicity of RISC can make some operations less straightforward, requiring more
instructions to accomplish tasks that might be single instructions in CISC architectures.(Dis -
Adv)
Examples of a RISC are - ARM (Advanced RISC Machine), MIPS (Microprocessor without
Interlocked Pipeline Stages) , Powerpc
6. RISC
1. Simple and small instruction set.
2. Instructions are simpler and uniform.
3. Well-suited for pipelining due to uniform
instructions
4. Often follows a "load-store" model,
minimizing memory-to-memory operations.
5. Compiler-friendly architecture, making
code optimization easier.
6. Applications are Embedded systems,
mobile devices, IoT, networking equipment,
DSPs.
CISC
1. Large and complex instruction set.
2. Instructions can be complex and varied.
3. Complex instructions can hinder
pipelining.
4. Supports memory-to-memory operations
directly.
5. May require more effort from compilers for
optimization.
6. General-purpose computing, legacy
systems, desktops, servers.
COMPARISON
7. Instruction set Architecture (ISA)
ISA stands for "Integrated System Architecture." ISA in VLSI refers to the overall architecture
and design of an integrated system or chip that includes multiple components and functions.
It encompasses the arrangement and interaction of various components like processors,
memory units, input/output interfaces, and other peripherals on a single chip or within a
system.
A in VLSI involves defining the communication protocols, data buses, control signals, and the
organization of the entire system on a chip (SoC) or integrated circuit.
ISA focuses on how the different elements within the VLSI system work together to achieve
specific functionality and goals.
