2. RISC Design Philosophy
The Reduced Instruction Set Computing (RISC) architecture prioritizes
simplicity, high clock speed, and software flexibility.
It emphasizes delivering powerful yet straightforward instructions. This
philosophy contrasts with the Complex Instruction Set Computing (CISC)
approach, which leans heavily on hardware for instruction functionality.
3. RISC Design Rules
Instructions
RISC processors have
a limited number of
instruction classes,
each providing simple
operations.
Complex operations
are synthesized by
combining simple
instructions, enhancing
pipeline efficiency.
Pipelines
Instruction processing
is divided into smaller
units for parallel
execution, advancing
by one step per cycle.
Decoded in one stage,
eliminating the need for
microcode as in CISC
processors.
Registers
RISC machines boast
large general-purpose
register sets,
functioning as a fast
local memory store for
all data.
In contrast, CISC
processors have
dedicated registers
for specific
purposes.
Load-store
architecture
The processor operates on
data held in registers.
Separate load and store
instructions transfer data
between the register bank
and external memory.
Memory accesses are costly, so
separating memory accesses from
data processing provides an
advantage.
4. RISC vs CISC Comparison
RISC
• Emphasizes a simple set of instructions.
• Each instruction performs a specific and simple operation.
• Optimized for fast execution with a focus on single-
cycle instruction
CISC
• Utilizes a large and varied set of instructions.
• Single instructions can perform complex operations.
• Designed to reduce the number of instructions
needed for a specific task..
5. RISC Benefits
Simplified
Instructions
Allow for high clock
speed and single-cycle
execution.
Software Flexibility
Greater intelligence due
to reduced hardware
complexity.
Efficiency
Achieved through fixed-
length instructions and
parallel execution in
pipelines.
6. RISC Architecture Overview
1 Simplicity & Speed
Characterized by
simplicity, speed, and
a focus on software
flexibility.
2 Contrast with
CISC
Highlighting the
hardware-dependent
complexity of CISC.
3 Design Principles
Contribute to efficient
and high-performance
processors.
7. ARM Design Philosophy
Portable Embedded
Systems
ARM processors are
designed with a focus on
physical features tailored to
portable embedded
systems.
Reduce Power
Consumption
Emphasizing the reduction
of power consumption for
extended battery life,
crucial for mobile devices
like phones and PDAs.
Code Density
Essential for embedded
systems with limited
memory due to cost and
size constraints.
8. Key Requirements of ARM Design
1 Price-Sensitive Environment
Utilizing slow and low-cost memory devices in price-sensitive embedded systems.
2 Cost-Effectiveness
Aiming to reduce the die area occupied by the processor for cost-effectiveness.
3 Hardware Debug Technology
Inclusion of hardware debug technology for software engineers to monitor
code execution, aiding issue resolution and reducing development costs.
9. ARM Core Adaptations for Embedded
Systems
Hybrid Architecture
ARM core not a pure RISC
architecture due to the
constraints of embedded
systems.
Performance & Power
Consumption
Focusing on total effective
system performance and
power consumption over raw
processor speed.
Code Optimization
Introduction of Thumb 16-bit
instruction set for improved
code density.
10. ARM Instruction Set for Embedded
Systems
Variable Cycle Execution
Enhances performance and code density for specific
instructions like load-store-multiple instructions.
Code Density Enhancement
Inline barrel shifter adds complexity but enhances core
performance and code density.
Thumb 16-bit instruction set
Support fast operations, including DSP instructions for 16×16-
bit multiplier operations.
Conditional execution
This feature improves performance and code density by reducing
Branch instructions
Enhanced Instructions
These instructions allow a faster-performing ARM processor in
some cases to replace the traditional combinations of a processor plus a DSP
11. ARM's Popularity in Embedded
Systems
1 Global Adoption
ARM processor's
additional features
make it widely used in
32-bit embedded
systems.
2 Global Production
Many top
semiconductor
companies globally
produce products
based on the ARM
processor.
3 Diverse
Applications
ARM's adaptability
and features
contribute to its
popularity in diverse
embedded
