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Computer Systems

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Introduction – What is a Computer?

• This course is all about how computers work

• What do computer and computer system mean to you?

• But what do we mean by a computer?

– Different types: desktop, servers, embedded devices

– Different uses: automobiles, graphics, finance, genomics…

– Different manufacturers: Intel, Apple, IBM, Microsoft, Sun…

– Different underlying technologies and different costs!

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What is a Computer System?

• Hardware + Software

• Hardware

– Physical components making up the computer system

– Things making noises when you drop a computer

• Software

– Programs controlling the operations of computer

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What is a Computer System?

• Hardware Components:

– input (mouse, keyboard, disk drives, network)

– output (display, printer, disk drives, network)

– memory (disk drives, DRAM, SRAM, CD)

– processor (datapath and control)

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Hardware Components

• Hardware components diagram

– Interconnected by bus

CPUCPU MemoryMemory

BusBus

I/OI/OControllerController

I/OI/OControllerController

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Software Components

From High-Level Language to Machine Language

Applications

High Level Languages

Assembly Languages

Hardware

68000, Intel x86, MIPS

C, JAVA

Web Browsers, Games, Word, Excel

HLL ComplierAssembly Language AssemblerMachine Language

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Why learn this stuff?

• You want to call yourself a “computer scientist”

– Computer science is not just about software development

• Improve software performance

– Understand what’s under the hood helps in many ways

• Both Hardware and Software affect performance:

– Algorithm determines number of source-level statements

– Language/Compiler/Architecture determine machine instructions

– Processor/Memory determine how fast instructions are executed

• You need to make a purchasing decision or offer “expert” advice

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Why learn this stuff?

• Assess and Understand Performance

• Understand how software features are supported by hardware

• Lay the foundation for studying other important subjects in Computer Science, such as programming languages, complier, operating system, & computer architecture

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How do we learn this stuff?

• As seen earlier:

– Different types, uses, manufacturers, underlying technologies, and costs!

• Analogy: Consider a course on “automotive vehicles”

– Many similarities from vehicle to vehicle (e.g., wheels)

– Huge differences from vehicle to vehicle (e.g., gas vs. electric)

• Best way to learn:

– Focus on a specific instance and learn how it works

– While learning general principles and historical perspectives

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How do we learn this stuff? Abstraction

• The computer system and its components are complicated! E.g.,– The processor is implemented using millions of transistors– It is impossible to understand by looking at each transistor– We need ...

• Abstraction – A model that renders lower-level details of computer systems

temporarily invisible in order to facilitate design of sophisticated systems

– Delving into the depths reveals more information

• An abstraction omits unneeded detail, helps us cope with complexity

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How do we learn this stuff? Abstraction

• Abstraction is one of the most important concepts (BIG IDEAS) and problem solving techniques a CS major needs to learn and master!

• Being able to think in multiple levels of abstraction separate Computer Science from other disciplines!!

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How do computers work?

• Need to understand abstractions such as:

– Applications software

– Systems software

– Assembly Language

– Machine Language

– Architectural Issues

– Sequential logic, finite state machines

– Combinational logic, arithmetic circuits

– Boolean logic, 1s and 0s

– Transistors used to build logic gates (CMOS)

– Semiconductors/Silicon used to build transistors

– Properties of atoms, electrons, and quantum dynamics

• So much to learn!

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Instruction Set Architecture

• A very important abstraction

– interface between hardware and low-level software

– standardizes instructions, machine language bit patterns, etc.

– advantage: different implementations of the same architecture

• Modern instruction set architectures:

– Motorola 68000, PowerPC, Intel x86, IA-32, MIPS, SPARC, ARM, and others

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Computer Architecture vs Organization

• Architecture is those attributes visible to the programmer– Abstraction of internal organization of a computer– Defines capabilities of computer and its programming model– Instruction set, number of bits used for data representation,

I/O mechanisms, addressing techniques.– e.g. Is there a multiply instruction?

• Organization is how features are implemented– Control signals, interfaces, memory technology.– e.g. Is there a hardware multiply unit or is it done by repeated

addition?

• More examples can be found as we study along …– Architecture:– Organization:

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Computer Architecture vs Organization

• All Intel x86 family share the same basic architecture

• The IBM System/370 family share the same basic architecture

• This gives code compatibility

– At least backwards

• Organization differs between different versions

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Historical Perspective

• ENIAC built in World War II was the first general purpose computer– Electronic Numerical Integrator And Computer– Eckert and Mauchly, University of Pennsylvania– Used for computing artillery firing tables – Started 1943, Finished 1946 – Too late for war effort (Quiz: WWII ended in _?)– Used until 1955– 80 feet long by 8.5 feet high and several feet wide– Decimal (not binary)– Programmed manually by switches – Each of the twenty 10 digit registers was 2 feet long– Used 18,000 vacuum tubes, 70,000 resistors, 10,000

capacitors, 6,000 switches– 30 tons, 15,000 square feet, 140 KW power consumption– Performed 1900 additions per second

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Von Neumann Machine

• Model of modern general purpose electronic digital computers

• Program and data are stored in the common memory system

• Pseudocode of operation

DO

BEGIN

Read an instruction from memory (Fetch)

Execute the instruction (Excecute)

END

REPEAT FOREVER

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Topics of This Class

• Introduction

• Data Representation

• Instruction Set Architecture

• Assembly Language Programming

• Structure of CPU

• Accelerating Performance

• RISC

• Interrupts and I/O Techniques

• Memory Hierarchy

• Operating System

• Computer Networking