RISC and CISC architectures evolved from different philosophies but have converged over time. CISC aimed to optimize for simpler compilers by incorporating complex instructions while RISC focused on optimized hardware using reduced, uniform instruction sets. While CISC was better for early computers with slow memory, RISC emerged to improve performance. Advances now blur the lines as CISC uses pipelining and RISC supports more instructions, showing how the strategies have influenced each other in modern processors.
CISC & RISC Architecture with contents
History Of CISC & RISC
Need Of CISC
CISC
CISC Characteristics
CISC Architecture
The Search for RISC
RISC Characteristics
Bus Architecture
Pipeline Architecture
Compiler Structure
Commercial Application
Reference
1. CISC VS. RISC.
2. Agenda.
3. CPU Architecture.
4. Instruction Set Architecture (ISA). Group of instructions to execute a program. Instructions are in the form of: Opcode + Operand. An agreement between hardware and human for making interaction. Example : ADD R1, R2, R3
Can be represented as :
00101111100001111001010101010101
10111010100011110101001011011010
Two major schools of ISA: CISC & RISC.
5. CISC Philosophy (Complex Instruction Set Computing). The primary goal is to complete a task in as few lines as possible. Used on PCs and laptops that need to process heavy graphics and computations. Each instruction consist of one step.
(ex: MULT 2:3, 5:2, load the two values into registers, multiplies the operands, and then stores the product in appropriate register).
6. CISC Pros & Cons. Instruction size is different from one operation to another. Operation size is smaller but no of cycles are more. Needs better hardware and powerful processing. Performance is slow due to the amount of clock time taken by different instructions.
7. RISC Philosophy (Reduced Instruction Set Computing). Use only simple instructions that can be executed within one clock cycle. Keep all instructions of same size. Allow only load/store instruction to access the memory.
(ex: MULT command divided into three separate commands:LOAD, PROD, and STORE).
8. RISC Pros & Cons. Allow free use of microprocessors space because of its simplicity. Needs large memory caches on the chip itself so require very fast memory. Give support for high level languages (like C, C++, Java). Performance depends on the programmer or compiler.
9. CPU Performance Equation. The following equation is commonly used for expressing a computer's performance ability:
퐶푃푈 푇푖푚푒=푆푒푐표푛푑푠/푃푟표푔푟푎푚=퐼푛푠푡푟푢푐푡푖표푛푠/푃푟표푔푟푎푚 푥 퐶푦푐푙푒푠/퐼푛푠푡푟푢푐푡푖표푛푠 푥 푆푒푐표푛푑푠/퐶푦푐푙푒
CISC minimize the number of instructions per program.
RISC does the opposite, reduce the cycles per instruction.
10. Summary.
RISC - Reduced Instruction Set ComputingTushar Swami
A detailed presentation about what is RISC and some of the basic differences between RISC and CISC Computers.
Also enlisting some of the major applications of RISC in the field of Technology.
CISC & RISC Architecture with contents
History Of CISC & RISC
Need Of CISC
CISC
CISC Characteristics
CISC Architecture
The Search for RISC
RISC Characteristics
Bus Architecture
Pipeline Architecture
Compiler Structure
Commercial Application
Reference
1. CISC VS. RISC.
2. Agenda.
3. CPU Architecture.
4. Instruction Set Architecture (ISA). Group of instructions to execute a program. Instructions are in the form of: Opcode + Operand. An agreement between hardware and human for making interaction. Example : ADD R1, R2, R3
Can be represented as :
00101111100001111001010101010101
10111010100011110101001011011010
Two major schools of ISA: CISC & RISC.
5. CISC Philosophy (Complex Instruction Set Computing). The primary goal is to complete a task in as few lines as possible. Used on PCs and laptops that need to process heavy graphics and computations. Each instruction consist of one step.
(ex: MULT 2:3, 5:2, load the two values into registers, multiplies the operands, and then stores the product in appropriate register).
6. CISC Pros & Cons. Instruction size is different from one operation to another. Operation size is smaller but no of cycles are more. Needs better hardware and powerful processing. Performance is slow due to the amount of clock time taken by different instructions.
7. RISC Philosophy (Reduced Instruction Set Computing). Use only simple instructions that can be executed within one clock cycle. Keep all instructions of same size. Allow only load/store instruction to access the memory.
(ex: MULT command divided into three separate commands:LOAD, PROD, and STORE).
8. RISC Pros & Cons. Allow free use of microprocessors space because of its simplicity. Needs large memory caches on the chip itself so require very fast memory. Give support for high level languages (like C, C++, Java). Performance depends on the programmer or compiler.
9. CPU Performance Equation. The following equation is commonly used for expressing a computer's performance ability:
퐶푃푈 푇푖푚푒=푆푒푐표푛푑푠/푃푟표푔푟푎푚=퐼푛푠푡푟푢푐푡푖표푛푠/푃푟표푔푟푎푚 푥 퐶푦푐푙푒푠/퐼푛푠푡푟푢푐푡푖표푛푠 푥 푆푒푐표푛푑푠/퐶푦푐푙푒
CISC minimize the number of instructions per program.
RISC does the opposite, reduce the cycles per instruction.
10. Summary.
RISC - Reduced Instruction Set ComputingTushar Swami
A detailed presentation about what is RISC and some of the basic differences between RISC and CISC Computers.
Also enlisting some of the major applications of RISC in the field of Technology.
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
Benefits:-
# Students can catch up on notes they missed because of an absence.
# Underachievers can find peer developed notes that break down lecture and study material in a way that they can understand
# Students can earn better grades, save time and study effectively
Our Vision & Mission – Simplifying Students Life
Our Belief – “The great breakthrough in your life comes when you realize it, that you can learn anything you need to learn; to accomplish any goal that you have set for yourself. This means there are no limits on what you can be, have or do.”
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Computer Architecture – An IntroductionDilum Bandara
Overview on high-level design of internal components of a computer. Cover step-by-step execution of a program through ALU while accessing & updating registers
RISC (reduced instruction set computer)LokmanArman
RISC
Reduced Instruction Set Computer
What Is RISC?
History Of RISC.
Characteristics Of RISC.
Five Design Principles Of RISC.
What Actually RISC Does?
In Real Life Uses Of RISC In Computer Architecture.
Computer Architecture & Organization.
ARM (Advance RISC Machine) is one of the most licensed and thus widespread processor cores in the world.Used especially in portable devices due to low power consumption and reasonable performance.Several interesting extension available like THUMB instruction set and Jazelle Java Machine.
SYBSC IT SEM IV EMBEDDED SYSTEMS UNIT I Core of Embedded SystemsArti Parab Academics
Core of embedded systems: microprocessors and microcontrollers, RISC and CISC controllers, Big endian and Little endian processors, Application specific ICs, Programmable logic devices, COTS, sensors and actuators, communication interface, embedded firmware, other system components.
Student will be able to know that fundamental concepts behind computer organization. this PPT includes the following topics: Introduction
Functional Units of Computer
Number Representation and Arithmetic Operations
Memory Location and Addresses
Addressing Modes
Pipelining
Memory Hierarchy
I/O Organization
Control Signals Generation
EEPROM (also written E2PROM and pronounced "e-e-prom", "double-e prom", "e-squared", or simply "e-prom") stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration tables or device configuration.
Unlike bytes in most other kinds of non-volatile memory, individual bytes in a traditional EEPROM can be independently read, erased, and re-written.
When larger amounts of static data are to be stored (such as in USB flash drives) a specific type of EEPROM such as flash memory is more economical than traditional EEPROM devices. EEPROMs are organized as arrays of floating-gate transistors.
An EPROM usually must be removed from the device for erasing and programming, whereas EEPROMs can be programmed and erased in-circuit, by applying special programming signals. Originally, EEPROMs were limited to single byte operations which made them slower, but modern EEPROMs allow multi-byte page operations. It also has a limited life - that is, the number of times it could be reprogrammed was limited to tens or hundreds of thousands of times. That limitation has been extended to a million write operations in modern EEPROMs. In an EEPROM that is frequently reprogrammed while the computer is in use, the life of the EEPROM can be an important design consideration. It is for this reason that EEPROMs were used for configuration information, rather than random access memory.
FellowBuddy.com is an innovative platform that brings students together to share notes, exam papers, study guides, project reports and presentation for upcoming exams.
We connect Students who have an understanding of course material with Students who need help.
Benefits:-
# Students can catch up on notes they missed because of an absence.
# Underachievers can find peer developed notes that break down lecture and study material in a way that they can understand
# Students can earn better grades, save time and study effectively
Our Vision & Mission – Simplifying Students Life
Our Belief – “The great breakthrough in your life comes when you realize it, that you can learn anything you need to learn; to accomplish any goal that you have set for yourself. This means there are no limits on what you can be, have or do.”
Like Us - https://www.facebook.com/FellowBuddycom
Computer Architecture – An IntroductionDilum Bandara
Overview on high-level design of internal components of a computer. Cover step-by-step execution of a program through ALU while accessing & updating registers
RISC (reduced instruction set computer)LokmanArman
RISC
Reduced Instruction Set Computer
What Is RISC?
History Of RISC.
Characteristics Of RISC.
Five Design Principles Of RISC.
What Actually RISC Does?
In Real Life Uses Of RISC In Computer Architecture.
Computer Architecture & Organization.
ARM (Advance RISC Machine) is one of the most licensed and thus widespread processor cores in the world.Used especially in portable devices due to low power consumption and reasonable performance.Several interesting extension available like THUMB instruction set and Jazelle Java Machine.
SYBSC IT SEM IV EMBEDDED SYSTEMS UNIT I Core of Embedded SystemsArti Parab Academics
Core of embedded systems: microprocessors and microcontrollers, RISC and CISC controllers, Big endian and Little endian processors, Application specific ICs, Programmable logic devices, COTS, sensors and actuators, communication interface, embedded firmware, other system components.
Student will be able to know that fundamental concepts behind computer organization. this PPT includes the following topics: Introduction
Functional Units of Computer
Number Representation and Arithmetic Operations
Memory Location and Addresses
Addressing Modes
Pipelining
Memory Hierarchy
I/O Organization
Control Signals Generation
EEPROM (also written E2PROM and pronounced "e-e-prom", "double-e prom", "e-squared", or simply "e-prom") stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration tables or device configuration.
Unlike bytes in most other kinds of non-volatile memory, individual bytes in a traditional EEPROM can be independently read, erased, and re-written.
When larger amounts of static data are to be stored (such as in USB flash drives) a specific type of EEPROM such as flash memory is more economical than traditional EEPROM devices. EEPROMs are organized as arrays of floating-gate transistors.
An EPROM usually must be removed from the device for erasing and programming, whereas EEPROMs can be programmed and erased in-circuit, by applying special programming signals. Originally, EEPROMs were limited to single byte operations which made them slower, but modern EEPROMs allow multi-byte page operations. It also has a limited life - that is, the number of times it could be reprogrammed was limited to tens or hundreds of thousands of times. That limitation has been extended to a million write operations in modern EEPROMs. In an EEPROM that is frequently reprogrammed while the computer is in use, the life of the EEPROM can be an important design consideration. It is for this reason that EEPROMs were used for configuration information, rather than random access memory.
This slide contain the detail about the various organization of computer(Register based organization, Stack Based Organization and Accumulator Based Organization), Addressing Modes, Instruction Formats and finally RISC and CISC
Dsdco IE: RISC and CISC architectures and design issuesHome
RISC is an alternative to the Complex Instruction Set Computing (CISC) architecture and is often considered the most efficient CPU architecture technology available today.
A 64-Bit RISC Processor Design and Implementation Using VHDL Andrew Yoila
1. Introduction
In today technology digital hardware plays a very important role in field of electronic and computer engineering products today. Due
to fast growing and competition in the technological world and rapid rise of transistor demand and speediness of joined circuits and
steeps declines of the price cause by the improvement in micro-electronics application Machineries. The introduction of computer to
the society has affected so many things in the society in which almost all problems can be solve using computers. Many industries
today are requesting for system developers that have the skills and technical knowhow of designing the program logics. VHDL is one
of the most popular design applications used by designer to implement such task. Reduce instruction set computing (RISC) processor
play a vital role with RISC AND BIST features which most dominants patterns can provide, in systems testing of the circuits below
the tests which is important to the quality component of testing [1]. Although the Reduced instruction set have few instructions sets, as
its bit’s processing’s sizes increase then the test’s patterns become denser and the structure’s faults is kept great. In view to enable the
Operation of the most instructions as registers to registers operation, Arithmetic logic unit is studied and a detail test patterns is being
develop. This report is prepaid keeping in mind where specific application is automated and controlled. This report has 33 instruction
set with MICA architecture. This report will focus mainly on the meaning of
i. RISC processor,
ii. the design,
iii. the architecture,
iv. the data part and the instruction set of the design.
v. VHDL.
Question 1. please describe an embedded system in less than 100 word.pdfarmcomputers
Question 1. please describe an embedded system in less than 100 words. You will need to cover
all the major characteristics of the embedded system to earn full points.
Question 2. please explain RISC and CISC and give the advantages and disadvantages of both.
Solution
1.An embedded system is a combination of computer hardware and software and some additional
parts, either mechanical or electronic—designed to perform a dedicated function.
Example of embedded system is Digital Watch
It contains a simple, inexpensive 4-bit processor and its own on-chip ROM. The only other
hardware elements of the watch are the inputs (buttons) and outputs (display and speaker).It
consists of a software, which when carefully designed, allows enormous flexibility and helps to
create a reasonably reliable product at extraordinarily low production cost.
other examples are:Microwave oven, cordless phones, ATMS etc
2) RISC (Reduced Instruction Set Computer)
RISC stands for Reduced Instruction Set Computer.
To execute each instruction, if there is separate electronic circuitry in the control unit, which
produces all the necessary signals, this approach of the design of the control section of the
processor is called RISC design.It is also called hard-wired approach.
Examples of RISC processors:
IBM RS6000, MC88100
DEC’s Alpha 21064, 21164 and 21264 processors
Features of RISC Processors:
The standard features of RISC processors are listed below:
RISC processors use a small and limited number of instructions.
RISC machines mostly uses hardwired control unit.
RISC processors consume less power and are having high performance.
Each instruction is very simple and consistent.
RISC processors uses simple addressing modes.
RISC instruction is of uniform fixed length.
CISC (Complex Instruction Set Computer)
CISC stands for Complex Instruction Set Computer. If the control unit contains a number of
micro-electronic circuitry to generate a set of control signals and each micro-circuitry is
activated by a micro-code, this design approach is called CISC design.
Examples of CISC processors are:
Intel 386, 486, Pentium, Pentium Pro, Pentium II, Pentium III
Motorola’s 68000, 68020, 68040, etc.
Features of CISC Processors:
The standard features of CISC processors are listed below:
CISC chips have a large amount of different and complex instructions.
CISC machines generally make use of complex addressing modes.
Different machine programs can be executed on CISC machine.
CISC machines uses micro-program control unit.
CISC processors are having limited number of registers.
Advantages of CISC Architecture:
1)Microprogramming is easy to implement and much less expensive than hard wiring a control
unit.
2)It is easy to add new commands into the chip without changing the structure of the instruction
set as the architecture uses general-purpose hardware to carry out commands.
3)This architecture makes the efficient use of main memory since the complexity (or more
capability) of instruction allo.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
Have you ever wanted a Ruby client API to communicate with your web service? Smithy is a protocol-agnostic language for defining services and SDKs. Smithy Ruby is an implementation of Smithy that generates a Ruby SDK using a Smithy model. In this talk, we will explore Smithy and Smithy Ruby to learn how to generate custom feature-rich SDKs that can communicate with any web service, such as a Rails JSON API.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
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• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
2. Overview
History of CISC and RISC
CISC and RISC
Philosophy
Attributes and disadvantages
Summation
3. History of RISC/CISC
1950s IBM instituted a research program
1964 Release of System/360
Mid-1970s improved measurement tools demonstrated on CISC
1975 801 project initiated at IBM’s Watson Research Center
1979 32-bit RISC microprocessor (801) developed led by Joel Birnbaum
1984 MIPS developed at Stanford, as well as projects done at Berkeley
1988 RISC processors had taken over high-end of the workstation market
Early 1990s IBM’s POWER (Performance Optimization With Enhanced
RISC) architecture introduced w/ the RISC System/6k
AIM (Apple, IBM, Motorola) alliance formed, resulting in PowerPC
4. What is CISC?
CISC is an acronym for Complex Instruction Set Computer and are chips
that are easy to program and which make efficient use of memory. Since the
earliest machines were programmed in assembly language and memory
was slow and expensive, the CISC philosophy made sense, and was
commonly implemented in such large computers as the PDP-11 and the
DECsystem 10 and 20 machines.
Most common microprocessor designs such as the Intel 80x86 and Motorola
68K series followed the CISC philosophy.
But recent changes in software and hardware technology have forced a re-
examination of CISC and many modern CISC processors are hybrids,
implementing many RISC principles.
CISC was developed to make compiler development simpler. It shifts most
of the burden of generating machine instructions to the processor. For
example, instead of having to make a compiler write long machine
instructions to calculate a square-root, a CISC processor would have a built-
in ability to do this.
5. CISC Attributes
The design constraints that led to the development of CISC (small amounts of
slow memory and fact that most early machines were programmed in
assembly language) give CISC instructions sets some common
characteristics:
A 2-operand format, where instructions have a source and a destination.
Register to register, register to memory, and memory to register commands.
Multiple addressing modes for memory, including specialized modes for
indexing through arrays
Variable length instructions where the length often varies according to the
addressing mode
Instructions which require multiple clock cycles to execute.
E.g. Pentium is considered a modern CISC processor
6. Most CISC hardware architectures have several characteristics in
common:
Complex instruction-decoding logic, driven by the need for a single
instruction to support multiple addressing modes.
A small number of general purpose registers. This is the direct result
of having instructions which can operate directly on memory and the
limited amount of chip space not dedicated to instruction decoding,
execution, and microcode storage.
Several special purpose registers. Many CTSC designs set aside
special registers for the stack pointer, interrupt handling, and so on.
This can simplify the hardware design somewhat, at the expense of
making the instruction set more complex.
A 'Condition code" register which is set as a side-effect of most
instructions. This register reflects whether the result of the last
operation is less than, equal to, or greater than zero and records if
certain error conditions occur.
7. At the time of their initial development, CISC machines used available
technologies to optimize computer performance.
Microprogramniing is as easy as assembly language to implement,
and much less expensive than hardwiring a control unit.
The ease of microcoding new instructions allowed designers to
make CISC machines upwardly compatible: a new computer could
run the same programs as earlier computers because the new
computer would contain a superset of the instructions of the earlier
computers.
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.
Because microprogram instruction sets can be written to match the
constructs of high-level languages, the compiler does not have to be
as complicated.
8. CISC Disadvantages
Designers soon realised that the CISC philosophy had its own problems,
including:
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.
So that as many instructions as possible could be stored in memory with the
least possible wasted space, 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.
Many specialized instructions aren't used frequently enough to justify their
existence -approximately 20% of the available instructions are used in a
typical program.
CISC instructions typically set the condition codes as a side effect of the
instruction. Not only does setting the condition codes take time, but
programmers have to remember to examine the condition code bits before a
subsequent instruction changes them.
9. What is RISC?
RISC?
RISC, or Reduced Instruction Set Computer. is a type of microprocessor
architecture that utilizes a small, highly-optimized set of instructions, rather
than a more specialized set of instructions often found in other types of
architectures.
History
The first RISC projects came from IBM, Stanford, and UC-Berkeley in the
late 70s and early 80s. The IBM 801, Stanford MIPS, and Berkeley RISC 1
and 2 were all designed with a similar philosophy which has become known
as RISC. Certain design features have been characteristic of most RISC
processors:
one cycle execution time: RISC processors have a CPI (clock per instruction) of
one cycle. This is due to the optimization of each instruction on the CPU and a
technique called PIPELINING
pipelining: a techique that allows for simultaneous execution of parts, or stages,
of instructions to more efficiently process instructions;
large number of registers: the RISC design philosophy generally incorporates a
larger number of registers to prevent in large amounts of interactions with
memory
10. RISC Attributes
The main characteristics of CISC microprocessors are:
Extensive instructions.
Complex and efficient machine instructions.
Microencoding of the machine instructions.
Extensive addressing capabilities for memory operations.
Relatively few registers.
In comparison, RISC processors are more or less the opposite of the above:
Reduced instruction set.
Less complex, simple instructions.
Hardwired control unit and machine instructions.
Few addressing schemes for memory operands with only two basic
instructions, LOAD and
STORE
Many symmetric registers which are organised into a register file.
11. Pipelining
RISC Pipelines
A RISC processor pipeline operates in much the same way,
although the stages in the pipeline are different. While different
processors have different numbers of steps, they are basically
variations of these five, used in the MIPS R3000 processor:
- fetch instructions from memory
- read registers and decode the instruction
- execute the instruction or calculate an address
- access an operand in data memory
- write the result into a register
12. RISC Disadvantages
There is still considerable controversy among experts about the
ultimate value of RISC architectures. Its proponents argue that RISC
machines are both cheaper and faster, and are therefore the
machines of the future.
However, by making the hardware simpler, RISC architectures put a
greater burden on the software. Is this worth the trouble because
conventional microprocessors are becoming increasingly fast and
cheap anyway?
13. CISC versus RISC
CISC RISC
Emphasis on hardware Emphasis on software
Includes multi-clock
complex instructions
Single-clock,
reduced instruction only
Memory-to-memory:
"LOAD" and "STORE"
incorporated in instructions
Register to register:
"LOAD" and "STORE"
are independent instructions
Small code sizes,
high cycles per second
Low cycles per second,
large code sizes
Transistors used for storing
complex instructions
Spends more transistors
on memory registers
14. Summation
As memory speed increased, and high-level languages displaced assembly
language, the major reasons for CISC began to disappear, and computer
designers began to look at ways computer performance could be optimized
beyond just making faster hardware.
One of their key realizations was that a sequence of simple instructions
produces the same results as a sequence of complex instructions, but can
be implemented with a simpler (and faster) hardware design. (Assuming that
memory can keep up.) RISC (Reduced Instruction Set Computers)
processors were the result.
CISC and RISC implementations are becoming more and more alike. Many
of today’s RISC chips support as many instructions as yesterday's CISC
chips. And today's CISC chips use many techniques formerly associated
with RISC chips.
To some extent, the argument is becoming moot because CISC and RISC
implementations are becoming more and more alike. Many of today's RISC
chips support as many instructions as yesterday's CISC chips. And today's
CISC chips use many techniques formerly associated with RISC chips.
15. Modern Day Advancement
CISC and RISC Convergence
State of the art processor technology has changed significantly
since RISC chips were first introduced in the early '80s. Because a
number of advancements are used by both RISC and CISC
processors, the lines between the two architectures have begun to
blur. In fact, the two architectures almost seem to have adopted the
strategies of the other. Because processor speeds have increased,
CISC chips are now able to execute more than one instruction within
a single clock. This also allows CISC chips to make use of
pipelining. With other technological improvements, it is now possible
to fit many more transistors on a single chip.
16. This gives RISC processors enough space to incorporate more
complicated, CISC-like commands. RISC chips also make use of
more complicated hardware, making use of extra function units for
superscalar execution. All of these factors have led some groups to
argue that we are now in a "post-RISC" era, in which the two styles
have become so similar that distinguishing between them is no
longer relevant. However, it should be noted that RISC chips still
retain some important traits. RISC chips stricly utilize uniform,
single-cycle instructions. They also retain the register-to-register,
load/store architecture. And despite their extended instruction sets,
RISC chips still have a large number of general purpose registers.