Embedded systems introduction
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Embedded Systems Introduction. L1. References Embedded Systems Design, Steve Heath, Elsevier Embedded Systems Design, Frank Vahid & Tony Givargis, John wiley Fundamentals of embedded software, Daniel W lewis, Pearson education

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Embedded systems introduction

Embedded SystemsIntroduction

L1


Embedded systems introduction

  • References

  • Embedded Systems Design, Steve Heath, Elsevier

  • Embedded Systems Design, Frank Vahid & Tony Givargis, John wiley

  • Fundamentals of embedded software, Daniel W lewis, Pearson education

  • Embedded Microcomputer Systems, Jonathan W Valavano, Brooks/cole, Thomson Learning

  • Embedded Systems Design, Oliver Bailey, Dreamtech

  • Embedded Real-time Systems, K V K K Prasad, Dreamtech


Outline

Outline

  • Embedded systems overview

    • What are they?

  • Design challenge – optimizing design metrics

  • Technologies

    • Processor technologies

    • IC technologies

    • Design technologies


Embedded systems overview

Embedded systems overview

  • When we talk of microprocessors we think of computers as they are everywhere

  • Computers often mean

    • Desktop PC’s

    • Laptops

    • Mainframes

    • Servers

  • But there’s yet another type of computing system

    • Far more common...


Embedded systems overview1

Computers/ microprocessors are in here...

Embedded systems overview

  • Embedded computing systems

    • (Micro)processors are embedded within electronic devices, equipment, appliances

    • Hard to define - any computing system other than a desktop computer

    • Billions of units produced yearly, versus millions of desktop units

    • Perhaps 50 per household and per automobile

Toys, mobile phones, kitchen appliances, even pens 

Many times more processors used in each of them , though they cost much less

These processors make these devices sophisticated, versatile and inexpensive


A short list of embedded systems

A “short list” of embedded systems

Modems

MPEG decoders

Network cards

Network switches/routers

On-board navigation

Pagers

Photocopiers

Point-of-sale systems

Portable video games

Printers

Satellite phones

Scanners

Smart ovens/dishwashers

Speech recognizers

Stereo systems

Teleconferencing systems

Televisions

Temperature controllers

Theft tracking systems

TV set-top boxes

VCR’s, DVD players

Video game consoles

Video phones

Washers and dryers

Anti-lock brakes

Auto-focus cameras

Automatic teller machines

Automatic toll systems

Automatic transmission

Avionic systems

Battery chargers

Camcorders

Cell phones

Cell-phone base stations

Cordless phones

Cruise control

Curbside check-in systems

Digital cameras

Disk drives

Electronic card readers

Electronic instruments

Electronic toys/games

Factory control

Fax machines

Fingerprint identifiers

Home security systems

Life-support systems

Medical testing systems

And the list goes

on and on


Embedded systems introduction

Embedded systems

A microprocessor based system that is built to control a function(s) of a system and is designed not to be programmed by the user. (controller)

User could select the functionality but cannot define the functionality.

Embedded system is designed to perform one or limited number of functions, may be with choices or options.

PCs provide easily accessible methodologies, HW & SW that are used to build Embedded systems


Embedded systems introduction

Why did they become popular?

Replacement for discrete logic-based circuits

Functional upgradability ?, easy maintenance upgrades

Improves the performance of mechanical systems through close control

Protection of Intellectual property

Replacement of Analogue circuits (DSPs)


Embedded systems introduction

What does an Embedded system consist of?

Processor – Types, technologies, functionalities

Memory – how much, what types, organisation

Peripherals/ I/O interfaces – communicate with the user, external environment

Inputs and outputs / sensors & actuators – Digital - binary, serial/parallel, Analogue, Displays and alarms, Timing devices

SW – OS, application SW, initialisation, self check

Algorithms


Embedded systems introduction

Path of electronic design

Mechanical control systems- expensive & bulky

Discrete electronic circuits – fast but no flexibility

SW controlled circuits – microprocessors and controllers – slow, flexible

HW implementation of SW, HW & SW systems


Some common characteristics of embedded systems

Some Common Characteristics of Embedded Systems

  • Single-functioned

    • Executes a single program, repeatedly

  • Tightly-constrained

    • Low cost, low power, small, fast, etc.

  • Reactive and real-time

    • Continually reacts to changes in the system’s environment

    • Must compute certain results in real-time without delay


Embedded system digital camera

Digital camera chip

CCD

CCD preprocessor

Pixel coprocessor

D2A

A2D

lens

JPEG codec

Microcontroller

Multiplier/Accum

DMA controller

Display ctrl

Memory controller

ISA bus interface

UART

LCD ctrl

Embedded system - digital camera

  • Single-functioned -- always a digital camera

  • Tightly-constrained -- Low cost, low power, small, fast

  • Reactive and real-time -- only to a small extent


Design challenge optimizing design metrics

Design challenge – optimizing design metrics

  • Obvious design goal:

    • Construct an implementation with desired functionality

  • Key design challenge:

    • Simultaneously optimize numerous design metrics

  • Design metric

    • A measurable feature of a system’s implementation

    • Optimizing design metrics is a key challenge


Design challenge optimizing design metrics1

Design challenge – optimizing design metrics

  • Common metrics

    • Unit cost: the monetary cost of manufacturing each copy of the system, excluding NRE cost

    • NRE cost (Non-Recurring Engineering cost): The one-time monetary cost of designing the system

    • Size: the physical space required by the system

    • Performance: the execution time or throughput of the system

    • Power: amount of power consumed by the system

    • Flexibility: the ability to change the functionality of the system without incurring heavy NRE cost


Design challenge optimizing design metrics2

Design challenge – optimizing design metrics

  • Common metrics (continued)

    • Time-to-prototype: the time needed to build a working version of the system

    • Time-to-market: the time required to develop a system to the point that it can be released and sold to customers

    • Maintainability: the ability to modify the system after its initial release

    • Correctness, safety, many more


Design metric competition improving one may worsen others

Expertise with both software and hardware is needed to optimize design metrics

A designer must be comfortable with various technologies in order to choose the best for a given application and constraints

Digital camera chip

CCD

CCD preprocessor

Pixel coprocessor

D2A

A2D

lens

JPEG codec

Microcontroller

Multiplier/Accum

DMA controller

Display ctrl

Memory controller

ISA bus interface

UART

LCD ctrl

Design metric competition -- improving one may worsen others

Power

Performance

Size

NRE cost

Hardware

Software


Time to market a demanding design metric

Time required to develop a product to the point it can be sold to customers

Market window

Period during which the product would have highest sales

Average time-to-market constraint is about 8 months

Delays can be costly

Time-to-market: a demanding design metric

Revenue

Time (months)


Losses due to delayed market entry

Simplified revenue model

Product life = 2W, peak at W

Time of market entry defines a triangle, representing market penetration

Triangle area equals revenue

Loss

The difference between the on-time and delayed triangle areas

Peak revenue

Peak revenue from delayed entry

Revenues ($)

On-time

Market fall

Market rise

Delayed

D

W

2W

On-time Delayed

entry entry

Time

Losses Due to Delayed Market Entry


Losses due to delayed market entry cont

Area = 1/2 * base * height

On-time = 1/2 * 2W * W

Delayed = 1/2 * (W-D+W)*(W-D)

Percentage revenue loss =

(D(3W-D)/2W2)*100%

Try some examples

Peak revenue

Peak revenue from delayed entry

Revenues ($)

On-time

Market fall

Market rise

Delayed

D

W

2W

On-time Delayed

entry entry

Time

Losses due to delayed market entry (cont.)

  • Lifetime 2W=52 wks, delay D=4 wks

  • (4*(3*26 –4)/2*26^2) = 22%

  • Lifetime 2W=52 wks, delay D=10 wks

  • (10*(3*26 –10)/2*26^2) = 50%

  • Delays are costly!


Nre and unit cost metrics

Costs:

Unit cost: the monetary cost of manufacturing each copy of the system, excluding NRE cost

NRE cost (Non-Recurring Engineering cost): The one-time monetary cost of designing the system

total cost = NRE cost + unit cost * # of units

per-product cost = total cost / # of units

= (NRE cost / # of units) + unit cost

Amortizing NRE cost over the units results in an additional Rs 200 per unit

NRE and Unit Cost Metrics

  • Example

    • NRE= Rs 20000, unit= Rs100

    • For 100 units

      • total cost = 20000 + 100*100 = 30000

      • per-product cost = 30,000/100 or 20000/100 + 100 = 300


Nre and unit cost metrics1

Compare technologies by costs -- best depends on quantity !

Technology A: NRE=Rs 5,000, unit=Rs 100

Technology B: NRE=Rs 1,00,000, unit=Rs 25

Technology C: NRE=Rs10,00,000, unit= Rs 2

NRE and unit cost metrics


The performance design metric

The performance design metric

  • Widely-used measure of system, widely-abused

    • Clock freq, instructions per second – not good measures

    • Digital camera example – a user cares about how fast it processes images, not clock speed or instructions per second

  • Latency (response time)

    • Time between task start and end

    • e.g., Camera’s A and B process images in 0.25 & 0.3 seconds

  • Throughput

    • Tasks per second, e.g. Camera A processes 4 images & B say 8 images per second

    • Throughput can be more than latency seems to imply due to concurrency, (by capturing a new image while previous image is being stored).

  • Speedup of B over S = B’s performance / A’s performance

    • Throughput speedup = 8/4 = 2


Three key embedded system technologies

Three key embedded system technologies

  • Technology

    • A manner of accomplishing a task, especially using technical processes, methods, or knowledge

  • Three key technologies for embedded systems

    • Processor technology

    • IC technology

    • Design technology


Processor technology

Processor technology

  • The architecture of the computation engine used to implement a system’s desired functionality

  • Processor does not have to be programmable

    • “Processor” not equal to general-purpose processor

Controller

Controller

Datapath

Datapath

Controller

Datapath

Control

logic

index

Control

logic and State register

Control logic and State register

Registers

Register

file

total

Custom

ALU

State register

+

General

ALU

IR

PC

IR

PC

Data

memory

Data

memory

Program memory

Program memory

Data

memory

Assembly code for:

total = 0

for i =1 to …

Assembly code for:

total = 0

for i =1 to …

Single-purpose

(“hardware”)

General-purpose

(“software”)

Application

-specific


Processor technology1

Processor technology

  • Processors vary in their customization for the problem at hand

total = 0

for i = 1 to N loop

total += M[i]

end loop

Desired functionality

General-purpose processor

Application-specific processor

Single-purpose processor


General purpose processors

Controller

Data path

Control

logic and State register

Register

file

General

ALU

IR

PC

Program memory

Data

memory

Assembly code for:

total = 0

for i =1 to …

General-purpose processors

  • Programmable device used in a variety of applications

    • Also known as “microprocessor”

  • Features

    • Program memory

    • General datapath with large register set and general ALU

  • User benefits

    • Low time-to-market and NRE costs

    • High flexibility

  • “Pentium” the most well-known, but there are hundreds of others


Single purpose processors

Datapath

Controller

Control logic

index

total

State register

+

Data

memory

Single-purpose processors

  • Digital circuit designed to execute exactly one program

    • Ex. coprocessor, accelerator

      Features

    • Contains only the components needed to execute a single program

    • No program memory

  • Benefits

    • Fast

    • Low power

    • Small size


Application specific instruction set processors

Controller

Datapath

Control

logic and State register

Registers

Custom

ALU

IR

PC

Data

memory

Program memory

Assembly code for:

total = 0

for i =1 to …

Application-specific Instruction set Processors

  • Programmable processor optimized for a particular class of applications having common characteristics

    • Compromise between general-purpose and single-purpose processors

  • Features

    • Program memory

    • Optimized datapath

    • Special functional units

  • Benefits

    • Some flexibility, good performance, size and power


Ic technology

IC technology

  • The manner in which a digital (gate-level) implementation is mapped onto an IC

    • IC: Integrated circuit, or “chip”

    • IC technologies differ in their customization to a design

    • IC’s consist of numerous layers (perhaps 10 or more)

      • IC technologies differ with respect to who builds each layer & when

gate

oxide

IC package

IC

drain

channel

source

Silicon substrate


Ic technology1

IC technology

  • Three types of IC technologies

    • Full-custom/VLSI

    • Semi-custom ASIC (gate array and standard cell)

    • PLD (Programmable Logic Device)


Full custom vlsi

Full-custom/VLSI

  • All layers are optimized for an embedded system’s particular digital implementation

    • Placing transistors

    • Sizing transistors

    • Routing wires

  • Benefits

    • Excellent performance, small size, low power

  • Drawbacks

    • High NRE cost (e.g., Rs 2 M), long time-to-market


Semi custom

Semi-custom

  • Lower layers are fully or partially built

    • Designers are left with routing of wires and maybe placing some blocks

  • Benefits

    • Good performance, good size, less NRE cost than a full-custom implementation (perhaps $10k to $100k)

  • Drawbacks

    • Still require weeks to months to develop


Pld programmable logic device

PLD (Programmable Logic Device)

  • All layers already exist

    • Designers can purchase an IC

    • Connections on the IC are either created or destroyed to implement desired functionality

    • Field-Programmable Gate Array (FPGA) very popular

  • Benefits

    • Low NRE costs, almost instant IC availability

  • Drawbacks

    • Bigger, expensive (perhaps Rs 2000 per unit), power hungry, slower


Moore s law

Moore’s law

  • The most important trend in embedded systems

    • Predicted in 1965 by Intel co-founder Gordon Moore

      IC transistor capacity has doubled roughly every 18 months for the past several decades

10,000

Logic transistors per chip

(in millions)

1,000

100

10

1

0.1

Note: logarithmic scale

0.01

0.001

1985

1987

1989

1991

1993

1995

1997

2003

2005

2007

2009

1981

1983

1999

2001


Moore s law1

Moore’s law

  • This growth rate is hard to imagine, most people underestimate


Graphical illustration of moore s law

Graphical illustration of Moore’s law

  • Something that doubles frequently grows more quickly than most people realize!

    • A 2002 chip can hold about 15,000 1981 chips inside itself

1981

1984

1987

1990

1993

1996

1999

2002

10,000

transistors

150,000,000

transistors

Leading edge

chip in 1981

Leading edge

chip in 2002


Embedded systems introduction

Design of Embedded Systems (Wescon 1975)

  • “... avoid data processing aides such as assemblers, high-level languages, simulated systems, and control panels. These computer-aided design tools generally get in the way of cost-effective design and are more a result of the cultural influence of data processing, rather than a practical need.”

  • “bulk of real-world control problems require less than 2,000 instructions to implement. For this size of program computer aided design does little to improve the design approach and does a lot to separate the design engineer from intimate knowledge of his hardware.”


Embedded systems introduction

Design needs Design technology

Achieving the metrics + fast & reliably

Enhanced productivity

Design – single stage

Multi stage - several abstraction levels


Design technology

Design Technology

  • The manner in which we convert our concept of desired system functionality into an implementation

Compilation/

Synthesis

Libraries/

IP

Test/

Verification

Compilation/Synthesis: Automates exploration and insertion of implementation details for lower level.

System

specification

System

synthesis

Hw/Sw/

OS

Model simulat./

checkers

Hw-Sw

cosimulators

Behavioral

specification

Libraries/IP: Incorporates pre-designed implementation from lower abstraction level into higher level.

Cores

Behavior

synthesis

RT

components

HDL simulators

RT

specification

RT

synthesis

Test/Verification: Ensures correct functionality at each level, thus reducing costly iterations between levels.

Gate

simulators

Logic

specification

Gates/

Cells

Logic

synthesis

To final implementation


Embedded systems introduction

Compilation and synthesis

Specify in abstract manner and get lower level details

Libraries and IP - reusability

Are ICs a form of libraries?

How do cores differ from ICs

Test / verification

Simulation

HDL based simulations


Embedded systems introduction

Multiple perspectives for visualisation of a system

Functionality perspective

Environmental

User I/F or Operator perspective

System

Performance

Architectural perspective

Physical


Embedded systems introduction

Systematic Design of Embedded Systems

  • Most embedded systems are far too complex for Adhoc/empirical approach to design(100,000 lines)

  • Methodical, engineering-oriented, tool-based approach is essential

    • specification, synthesis, optimization, verification etc.

    • prevalent for hardware, still rare for software

  • One key aspect is the creation of models

    • Representation of knowledge and ideas about the system being developed - specification

    • Models only represent certain properties to be analyzed, understood & verified. They omit or modify certain details (abstraction) based on certain assumptions. One of the few tools available for dealing with complexity


Embedded systems introduction

Abstractions and Models

  • Models are foundations of science and engineering

  • Designs usually start with informal specifications

  • However, soon a need for Models and Abstractions is established

  • Models or abstractions have connections to Implementation (h/w, s/w) and Application

  • Two types of modeling: System structure & system behavior

    • The relationships, behavior and interaction of atomic components

    • Coordinate computation of & communication between components

  • Models from classical CS

    • FSM, RAM (von Neumann), CCS (Milner)

    • Turing machine, Universal Register Machine


Embedded systems introduction

Models

Conceptual model

Physical model

Analogue model

Mathematical model

Numerical model

Computational model

Implementation

Assumptions & accuracy


Embedded systems introduction

Good Models

  • Simple

    • Ptolemy vs. Galileo

  • Amenable for development of theory to reason

    • should not be too general

  • Has High Expressive Power

    • a game is interesting only if it has some level of difficulty!

  • Provides Ability for Critical Reasoning

    • Science vs. Religion

  • Practice is currently THE only serious test of model quality

  • Executable (for Simulation)

  • Synthesizable

  • Unbiased towards any specific implementation (h/w or s/w)


Modeling embedded systems

Modeling Embedded Systems

  • Functional behavior: what does the system do

    • in non-embedded systems, this is sufficient

  • Contract with the physical world

    • Time: meet temporal contract with the environment

      • temporal behavior important in real-time systems, as most embedded systems are

      • simple metric such as throughput, latency, jitter

      • more sophisticated quality-of-service metrics

    • Power: meet constraint on power consumption

      • peak power, average power, system lifetime

    • Others: size, weight, heat, temperature, reliability etc

      System model must support description of both

      functional behavior and physical interaction


Elements of a model of a computation system language

Elements of a Model of a Computation System: Language

  • Set of symbols with superimposed syntax & semantics

    • textual (e.g. matlab), visual (e.g. labview) etc.

  • Syntax: rules for combining symbols

    • well structured, intuitive

  • Semantics: rules for assigning meaning to symbols and combinations of symbols

    • without rigorous semantics, precise model behavior over time is not well defined

    • full executability and automatic h/w or s/w synthesis is impossible

    • E.g. operational semantics (in terms of actions of an abstract machine), denotational semantics (in terms of relations)


Simulation and synthesis

Simulation and Synthesis

  • Two sides of the same coin

  • Simulation: scheduling then execution on desktop computer(s)

  • Synthesis: scheduling then code generation in C++, C, assembly, VHDL, etc.

  • Validation by simulation important throughout design flow

  • Models of computation enable

    • Global optimization of computation and communication

    • Scheduling and communication that is correct by construction


Embedded systems introduction

Models Useful In Validating Designs

  • By construction

    • property is inherent.

  • By verification

    • property is provable.

  • By simulation

    • check behavior for all inputs.

  • By intuition

    • property is true. I just know it is.

  • By assertion

    • property is true. Would make something of it?

  • By intimidation

    • Don’t even try to doubt whether it is true

    • It is generally better to be higher in this list !


Embedded systems introduction

An embedded system is expected to receive inputs, process data or information, and provide outputs

The processing is done by processors

Before we build the processor we must know the expected behaviour of the processor

This is the model of the processor. We may call it a computational model. Before the processor is built it is in our mind.

We express this model through a description - text, graphics, or some formal language


Embedded systems introduction

Models & Languages

Models exist without language

Models are expressed in some language or the other

A model could be expressed in different languages

A language could express more than one model

Some languages are better suited to express some models


Embedded systems introduction

Types of models – many & include

Sequential model – A model that represents the embedded system as a sequence of actions.

A variety of systems need this sequence of steps. Most programming languages and natural languages can express this feature

Communicating-process model – A number of independent processes (may be sequential) communicate among themselves whilst doing their job. Synchronisation/signalling, passing data, mutual exclusion etc. Some languages are better suited.


Embedded systems introduction

State machine model – A model where the embedded system resides in a state till an input to the system/event makes it change its state. Most reactive and control system applications fall under this category. FSM representations are good way expressing the model.

Text Vs Graphic languages

Data flow model – An embedded system that functions mainly by transforming an input data stream into an output data stream – functioning of an mpeg camera – UML may be more useful. Most DSP applications


Embedded systems introduction

OO models – Well known – Useful for successive decomposition problems, problems where OO paradigm is useful etc.

Multiple models and multiple languages may be needed to describe a complex system.

The model description must be accompanied by semantic descriptions for proper processing


Embedded systems introduction

Lift model - English language description

Lift cage contains a number of controls – floor numbers, open and close door, it receives the data regarding the floor it is at. Users press the floor number to which they desire to go and depending upon the current location and the floor it has to go it moves up and down. Before it moves, the door is closed. On reaching the floor it keeps the door open for 15 sec, unless close door operation is executed before door closes. When stationary, door is kept closed. When moving in a direction it does not return to opposite direction, even on request, unless no request for higher or lower floor in the same direction is pending


Embedded systems introduction

  • Problems

  • Develop a model for the lift controller

  • Identify one problem each that fits into the models discussed above.

  • Develop a model for a data acquisition system that receives data from 14 channels through A/D converters and takes appropriate control actions as a function of the 14 inputs and communicates with 4 actuators. Inputs from channel 15 or 16 need immediate response, and the controller must respond in a time of about 20 clock cycles. In these cases, actuator 5 is activated.


Modeling approaches based on software design methods

Modeling Approaches based on Software Design Methods

  • No systematic design in 60s

  • From 70s, many different s/w design strategies

    • Design methods based on functional decomposition

      • Real-Time Structured Analysis and Design(RTSAD)

    • Design methods based on concurrent task structuring

      • Design Approach for Real-Time Systems (DARTS)

    • Design methods based on information hiding

      • Object-Oriented Design method (OOD)

    • Design methods based on modeling the domain

      • Jackson System Development method (JSD)

      • Object-Oriented Design method (OOD)


Continued

continued

  • UML is the latest manifestation

    • becoming prevalent in complex embedded system design


How models influence an application design

How Models Influence an Application Design?

  • Example: given input from a camera, digitally encode it using MPEG II encoding standards.

    • this task involves: storing the image for processing going through a number of processing steps, e.g., Discrete cosine transform (DCT), Quantization, encoding (variable length encoding), formatting the bit stream, Inverse Discrete Cosine transform (IDCT), ...

  • Is this problem appropriate for

    • Reactive Systems, Synchronous Data flow, CSP, ...

  • More than one model could be appropriate.


  • Choice of model

    Choice of Model

    • Model Choice: depends on

      • application domain

        • DSP applications use data flow models

        • Control applications use finite state machine models

        • Event driven applications use reactive models

      • efficiency of the model

        • in terms of simulation time

        • in terms of synthesized circuit/code.

    • Language Choice: depends on

      • underlying semantics

        • semantics in the model appropriate for the application.

      • available tools

      • personal taste and/or company policy


    Design productivity exponential increase

    Design productivity exponential increase

    • Exponential increase over the past few decades

    100,000

    10,000

    1,000

    Productivity

    (K) Trans./Staff – Mo.

    100

    10

    1

    0.1

    0.01

    1981

    2009

    1995

    2007

    1997

    1989

    1993

    1999

    2001

    1991

    1983

    2003

    1987

    1985

    2005


    The co design ladder

    The co-design ladder

    Sequential program code (e.g., C, VHDL)

    • In the past:

      • Hardware and software design technologies were very different

      • Recent maturation of synthesis enables a unified view of hardware and software

    • Hardware/software “codesign”

    Behavioral synthesis

    (1990's)

    Compilers

    (1960's,1970's)

    Register transfers

    Assembly instructions

    RT synthesis

    (1980's, 1990's)

    Assemblers, linkers

    (1950's, 1960's)

    Logic equations / FSM's

    Logic synthesis

    (1970's, 1980's)

    Machine instructions

    Logic gates

    Implementation

    VLSI, ASIC, or PLD implementation: “hardware”

    Microprocessor plus program bits: “software”

    The choice of hardware versus software for a particular function is simply a tradeoff among various design metrics, like performance, power, size, NRE cost, and especially flexibility; there is no fundamental difference between what hardware or software can implement.


    Independence of processor and ic technologies

    Independence of Processor and IC Technologies

    • Basic tradeoff

      • General vs. custom

      • With respect to processor technology or IC technology

      • The two technologies are independent

    Customized,

    providing improved:

    General-purpose

    processor

    ASIP

    Single-

    purpose

    processor

    General,

    providing improved:

    Power efficiency

    Performance

    Size

    Cost (high volume)

    Flexibility

    Maintainability

    NRE cost

    Time- to-prototype

    Time-to-market

    Cost (low volume)

    PLD

    Semi-custom

    Full-custom


    Design productivity gap

    Design productivity gap

    • While designer productivity has grown at an impressive rate over the past decades, the rate of improvement has not kept pace with chip capacity

    10,000

    100,000

    1,000

    10,000

    100

    1000

    Logic transistors per chip

    (in millions)

    Gap

    Productivity

    (K) Trans./Staff-Mo.

    10

    100

    IC capacity

    1

    10

    0.1

    1

    productivity

    0.01

    0.1

    0.001

    0.01

    1981

    1983

    1985

    1987

    1995

    1997

    1999

    2001

    2003

    2005

    2007

    2009

    1989

    1991

    1993


    Design productivity gap1

    Design productivity gap

    • 1981 leading edge chip required 100 designer months

      • 10,000 transistors / 100 transistors/month

    • 2002 leading edge chip requires 30,000 designer months

      • 150,000,000 / 5000 transistors/month

    • Designer cost increase from $1M to $300M


    The mythical man month

    The mythical man-month

    • The situation is even worse than the productivity gap indicates

    • In theory, adding designers to team reduces project completion time

    • In reality, productivity per designer decreases due to complexities of team management and communication

    • In the software community, known as “the mythical man-month” (Brooks 1975)

    • At some point, can actually lengthen project completion time! (“Too many cooks”)

    Team

    • 1M transistors, 1 designer=5000 trans/month

    • Each additional designer reduces for 100 trans/month

    • So 2 designers produce 4900 trans/month each

    15

    60000

    16

    16

    18

    50000

    19

    40000

    23

    24

    30000

    Months until completion

    20000

    43

    Individual

    10000

    0

    10

    20

    30

    40

    Number of designers


    Summary

    Summary

    • Embedded systems are everywhere

    • Key challenge: optimization of design metrics

      • Design metrics compete with one another

    • A unified view of hardware and software is necessary to improve productivity

    • Three key technologies

      • Processor: general-purpose, application-specific, single-purpose

      • IC: Full-custom, semi-custom, PLD

      • Design: Compilation/synthesis, libraries/IP, test/verification


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