This course is all about how computers work

1
Introduction
2
Introduction

• This course is all about how computers work
• 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!
• 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

3
Why learn this stuff?

• You want to call yourself a computer scientist
• You want to build software people use (need
  performance)
• You need to make a purchasing decision or offer
  expert advice
• Both Hardware and Software affect performance
• Algorithm determines number of source-level
  statements
• Language/Compiler/Architecture determine machine
  instructions (Chapter 2 and 3)
• Processor/Memory determine how fast instructions
  are executed (Chapter 5, 6, and 7)
• Assessing and Understanding Performance in
  Chapter 4

4
What is a computer?

• Components
• Input (mouse, keyboard)
• Output (display, printer)
• Memory (disk drives, DRAM, SRAM, CD)
• Network
• Our primary focus the processor (datapath and
  control)
• Implemented using millions of transistors
• Impossible to understand by looking at each
  transistor
• We need to learn the logical design of each
  component

5
Number of Distinct Processors Sold

• Embedded processors prevail
• Cell phones, car computers, digital TVs,
  videogame consoles,
• Designed to run dedicated applications
• Annual growth rate of 40
• 9 for desktops and servers

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Uniprocessor Performance
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Contributor 1 Technology

• Processor
• logic capacity about 30 per year
• clock rate about 20 per year
• Memory
• DRAM capacity about 60 per year (4x every 3
  years)
• Memory speed about 10 per year
• Cost per bit improves about 25 per year
• Disk
• capacity about 60 per year

8
Technology Improvement

• Moore's law
• The number of transistors per integrated circuit
  would double every 18 months

Gordon Moore (co-founder of Intel)
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Contributor 2 Computer Architecture

• Exploiting Parallelism (Single processor)
• Pipelining
• Superscalar
• VLIW (Very Long Instruction Word)
• Multiprocessor
• Media Instructions
• Cache Memory

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Advanced Architectural Features

• Parallelism in processing
• Instruction level parallelism (ILP)
• Superscalar
• Out of order execution
• Branch prediction
• VLIW (software approach)
• Data level parallelism (DLP) Task level
  parallelism (TLP)
• SIMD instructions (media processing)
• Multicore (multi-processor)
• Latency and capacity in memory system
• Low latency access using cache memory
• Capacity increase in main memory

11
Superscalar

• Multiple functional units
• Multiple integer units
• Multiple floating point units

12
How do computers work?

• Need to understand abstractions such as
• Applications software
• Systems software
• Assembly Language
• Machine Language
• Architectural Issues i.e., Caches, Virtual
  Memory, Pipelining
• 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!

13
Levels of Abstraction

• Delving into the depths reveals more information
  about machines
• An abstraction omits unneeded detail, helps us
  cope with complexity

14
Instruction Set Architecture (ISA)

• 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
• Disadvantage sometimes prevents using new
  innovations
• Design of instruction set
• How to specify data location
• Which instructions to include
• Which data formats to support
• How to encode instructions
• Modern instruction set architectures
• IA-32, PowerPC, MIPS, SPARC, ARM, and others

15
Historical Perspective

• ENIAC built in World War II
• The first general purpose computer
• Used for computing artillery firing tables
• 80 feet long by 8.5 feet high and several feet
  wide
• Each of the twenty 10 digit registers was 2 feet
  long
• Used 18,000 vacuum tubes
• Performed 1900 additions per second

Moores Law Transistor capacity doubles
every 18-24 months
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Before ENIAC
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Stored Program Computers

• Instructions and data stored as binary numbers in
  memory
• An instruction/data is referenced by its address
• Advent of EDVAC by John von Neumann

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Electronic Computers 2nd Generation

• Technologies
• Processor transistors
• Memory magnetic cores
• General purposes
• IBM System/360
• Same architecture for a wide range of computers
• Digital Equipment PDP-8
• Supercomputer
• Control Data 6600

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Electronic Computers 3rd Generation

• Technologies
• Processor IC
• Memory cores, SRAM and DRAM
• IBM S/370
• DEC PDP-11, VAX 11
• CDC 7600
• Cray-1

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Electronic Computers 4th Generation

• Technologies
• Processor VLSI
• Memory SRAM and DRAM
• IBM 3990, 4380
• DEC VAX 8400
• Vector supercomputers
• Cray-2, Cray X-MP
• Fujitsu, Hitachi, NEC

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Electronic Computers 5th Generation

• Technologies
• VLSI, SRAM, and DRAM with design tools
• Read Singularity is coming
• RISC processor
• MIPS
• PA-RISC
• SPARC
• Alpha
• PowerPC
• CISC processor
• Intel Pentium
• AMD

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Lessons from Computer History

• A new technology invents a new market
• IBM S/360 triggers business applications
• High density VLSI enables personal mobility
• Architecture is resurrected
• Simple one in 60 because of technology limit
• Complex one in 80 for servicing many people
• Simple one for mobility and low power
• Now?
• Mass market calls for standardization
• Niche market is profitable but vulnerable to new
  technology
• Cray, Apple, Sun, SGI