Abstraction And

Technology 1

Comp 411 – Fall 2006 8/28/06

Computer Abstractionsand Technology

1. Layer Cakes2. Computers are translators3. Switches and Wires

(Read Chapter 1)

Abstraction And

Technology 2

Comp 411 – Fall 2006 8/28/06

Computers Everywhere

∙ The computers we are used to- Desktops

- Laptops

- Embedded processors• Cars• Mobile phones• Toasters, irons, wristwatches, happy-meal toys

Abstraction And

Technology 3

Comp 411 – Fall 2006 8/28/06

Compiler for (i = 0; i < 3; i++) m += i*i;

Assembler and Linkeraddi $8, $6, $6 sll $8, $8, 4CPU

ModuleALU

A B

Cells A BCO CI S

FA

A Computer System∙ What is a computer system? ∙ Where does it start?∙ Where does it end?

Gates

Transistors

Abstraction And

Technology 4

Comp 411 – Fall 2006 8/28/06

Computer Layer Cake

∙ Applications∙ Systems software∙ Shared libraries∙ Operating System∙ Hardware – the bare metal

Hardware

Operating System

Libraries

Systems S/WAppsComputers are

digital Chameleons

Abstraction And

Technology 5

Comp 411 – Fall 2006 8/28/06

Computers are Translators

∙ User-Interface (visual programming)∙ High-Level Languages

- Compilers- Interpreters

∙ Assembly Language∙ Machine Language x: .word 0

y: .word 0c: .word 123456

...

lw $t0, xaddi $t0, $t0, -3lw $t1, ylw $t2, cadd $t1, $t1, $t2mul $t0, $t0, $t1sw $t0, y

int x, y;y = (x-3)*(y+123456)

Abstraction And

Technology 6

Comp 411 – Fall 2006 8/28/06

Computers are Translators

∙ User-Interface (visual programming)∙ High-Level Languages

- Compilers- Interpreters

∙ Assembly Language∙ Machine Language

x: .word 0y: .word 0c: .word 123456

...

lw $t0, xaddi $t0, $t0, -3lw $t1, ylw $t2, cadd $t1, $t1, $t2mul $t0, $t0, $t1sw $t0, y

0x04030201 0x08070605 0x00000001 0x000000020x00000003 0x00000004 0x706d6f43

Abstraction And

Technology 7

Comp 411 – Fall 2006 8/28/06

Why So Many Languages?

∙ Application Specific- Historically: COBOL vs. Fortran- Today: C# vs. Java

Visual Basic vs. Matlab

∙ Code Maintainability- High-level specifications are

easier to understand and modify

∙ Code Reuse∙ Code Portability∙ Virtual Machines

Abstraction And

Technology 8

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Abstraction And

Technology 9

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Abstraction And

Technology 10

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Cathode Ray Tube (CRT)The “last vacuum tube”Now nearing extinction

Abstraction And

Technology 11

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Liquid Crystal Displays (LCDs)

Abstraction And

Technology 12

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Abstraction And

Technology 13

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Abstraction And

Technology 14

Comp 411 – Fall 2006 8/28/06

Under the Covers

∙ Input∙Output∙ Storage∙Processing

- Datapath- Control

Intel Pentium III Xeon

Abstraction And

Technology 15

Comp 411 – Fall 2006 8/28/06

Implementation Technology

∙ Relays∙ Vacuum Tubes∙ Transistors∙ Integrated Circuits

- Gate-level integration- Medium Scale Integration (PALs)- Large Scale Integration (Processing unit on a chip)- Today (Multiple CPUs on a chip)

∙ Nanotubes??∙ Quantum-Effect Devices??

Abstraction And

Technology 16

Comp 411 – Fall 2006 8/28/06

openclosed

Implementation Technology

∙ Common Links?∙ A controllable switch∙ Computers are wires and switches

open

control

Abstraction And

Technology 17

Comp 411 – Fall 2006 8/28/06

Chips

∙ Silicon Wafers- Chip manufactures build many

copies of the same circuit onto a single wafer. Only a certain percentage of the chips will work; those that work will run at different speeds. The yield decreases as the size of the chips increases and the feature size decreases.

- Wafers are processed by automated fabrication lines. To minimize the chance of contaminants ruining a process step, great care is taken to maintain a meticulously clean environment.

Abstraction And

Technology 18

Comp 411 – Fall 2006 8/28/06

Field Effect Transistors (FETs)

∙ Modern silicon fabrication technology is optimized to build a particular type of transistor. The flow of electrons from the source to the drain is controlled by a gate voltage. Source DrainGate

Bulk

n+ n+

p

IDS = 0

VDS

Abstraction And

Technology 19

Comp 411 – Fall 2006 8/28/06

Chips

∙ Silicon Wafers

Metal 2

M1/M2 via

Metal 1

Polysilicon

Diffusion

Mosfet (under polysilicon gate)

IBM photomicrograph (Si has been removed!)

Abstraction And

Technology 20

Comp 411 – Fall 2006 8/28/06

How Hardware WAS Designed

∙ 20 years ago- I/O Specification

•Truth tables•State diagrams

- Logic design- Circuit design- Circuit Layout

Abstraction And

Technology 21

Comp 411 – Fall 2006 8/28/06

How Hardware IS Designed

∙ Today (with software)∙ High-level hardware specification languages

- Verilog- VHDL

Abstraction And

Technology 22

Comp 411 – Fall 2006 8/28/06

Reconfigurable Chips

∙ Programmable Array Logic (PALs)- Fixed logic / programmable wires

∙ Field Programmable Gate Arrays (FPGAs)- Repeated reconfigurable logic cells

Abstraction And

Technology 23

Comp 411 – Fall 2006 8/28/06

Death of Silicon Diversity

∙ In the future will there be more or fewer types of chips?

∙ Programmability = Flexibility∙ One chip can be programmed to perform many

functions∙ An ultra-flexible architecture might be

designed to emulate any function required∙ High-volumes might compensate for wasted

area∙ Computers are this ultimate circuit type∙ How many types of chips do we need?

- Memory chips- Logic Chips- Potato Chips (credit Anant Agrawal)

Abstraction And

Technology 24

Comp 411 – Fall 2006 8/28/06

Next Time

∙Computer Representations∙How is X represented in

computers?- X = text- X = numbers- X = anything else

∙Encoding Information