Computer Systems

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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

Memory
CPU
Bus
I/O Controller
I/O Controller
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Software Components
From High-Level Language to Machine Language
Applications
HLL ? Complier Assembly Language ?
Assembler Machine Language
High Level Languages
Assembly Languages
Hardware
68000, Intel x86, MIPS
C, JAVA
Web Browsers, Games, Word, Excel
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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 whats 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