Introduction

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

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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

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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 tran-

sistor We need to learn the logical design of each com-

ponent4

Embedded processors prevail Cell phones, car computers, digital TVs, videogame con-

soles, … Designed to run dedicated applications Annual growth rate of 40%

9% for desktops and servers

Number of Distinct Processors SoldM

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1998 1999 2000 2001 2002

Embedded computer

Desktops

Servers

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Uniprocessor Performance

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25%/year

52%/year

20%/year

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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

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Technology Improvement Moore's law

The number of transistors per inte-grated circuit would double every 18 months

Transi

stors

i80x86M68KMIPSAlpha

1970 1975 1980 1985 1990 1995 2000 2005

108

107

106

105

104

103

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Gordon Moore (co-founder of Intel)

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

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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

Superscalar Multiple functional units

Multiple integer units Multiple floating point units

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ALPHA Pentium

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 dynam-

ics

So much to learn!12

Levels of Abstraction Delving into the depths

reveals more information about machines

An abstraction omits unneeded detail, helps us cope with complexity

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High levellanguageprogram(in C)

Assemblylanguageprogram(for MIPS)

Binary machinelanguageprogram(for MIPS)

swap (int v[], int k){ int temp; temp = v[k]; v[k] = v[k+1]; v[k+1] = temp;}

swap: mull $2, $5, 4 add $2, $4, $2 lw $15, 0($2) lw $16, 4($2) sw $16, 0($2) sw $15, 4($2) jr $31

00000000101000010000000000011000000000000001100000011000001000011000110001100010000000000000000010001100111100100000000000000000101011001111001000000000000000001010110001100010000000000000010000000011111000000000000000001000

com-piler

assem-bler

Instruction Set Architecture (ISA) A very important abstraction

Interface between hardware and low-level soft-ware

Standardizes instructions, machine language bit patterns, etc.

Advantage: different implementations of the same architecture

Disadvantage: sometimes prevents using new in-novations

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

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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

Moore’s Law: Transistor capacity doubles every 18-24 months

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Historical Perspective

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

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