ECE 3400 Guest Lecture Design Principles and Methodologies ...cbatten/misc/batten... · What is Computer Architecture? Design Example • Design Principles • Design Methodologies

ECE 3400 Guest LectureDesign Principles and Methodologies in

Computer ArchitectureChristopher Batten

Computer Systems LaboratorySchool of Electrical and Computer Engineering

Cornell University

Spring 2014

• What is Computer Architecture? • Design Example Design Principles Design Methodologies

The Computer Engineering Stack

Technology

Application

Gap too large to bridge in one step(but there are exceptions, e.g., a magnetic compass)

ECE 3400 Design in Computer Architecture – Christopher Batten 2 / 30



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Instruction Set Architecture

Programming LanguageAlgorithm

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Sort an array of numbers2,6,3,8,4,5 -> 2,3,4,5,6,8

1. Find minimum number in input array2. Move minimum number into output array3. Repeat steps 1 and 2 until finished

Insertion sort algorithm

void isort( int b[], int a[], int n ) { for ( int idx, k = 0; k < n; k++ ) { int min = 100; for ( int i = 0; i < n; i++ ) { if ( a[i] < min ) { min = a[i]; idx = i; } } b[k] = min; a[idx] = 100; }}

C implementation of insertion sort





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Mac OS X, Windows, LinuxHandles low-level hardware management

blez $a2, donemove $a7, $zeroli $t4, 99move $a4, $a1move $v1, $zeroli $a3, 99lw $a5, 0($a4)addiu $a4, $a4, 4slt $a6, $a5, $a3movn $v0, $v1, $a6addiu $v1, $v1, 1movn $a3, $a5, $a6

MIPS32 Instruction SetInstructions that machine executes





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Silicon processtechnology

Si Si Si

SiSiSi

Transistors and wires

Combining devicesto do useful work

Boolean logic gatesand functions

How data flowsthrough system



What is Computer Architecture?

In its broadest definition, computer engineering is thedevelopment of the abstraction/implementation layers that allow us to

execute information processing applications efficientlyusing available manufacturing technologies


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Application Requirements • Suggest how to improve architecture • Provide revenue to fund development

Technology Constraints • Restrict what can be done efficiently • New technologies make new arch possible

Computer architects provide feedback to guideapplication and technology research directions



Computer Architecture in the ECE/CS Curriculum


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Gate Level ECE 2300 Digital Logic & Computer Org

ECE 3140 Embedded Systems

ECE 4750 Computer Architecture

ECE 4740 Digital VLSI Design

CS 4420 Compilers

Related Graduate Courses • ECE 5760 Advanced Microcontroller Design • ECE 5750 Advanced Computer Architecture • ECE 5730 Memory Systems • ECE 5770 Resilient Computer Systems • ECE 5745 Complex Digital ASIC Design • ECE 5775 High-Level Design Automation

CS 4410 Operating Systems



Logic, State, and Interconnect


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Interconnect

StateLogic StateLogic Logic

StateLogic StateLogicState

Digital systems are implemented with three basic building blocks • Logic to process data • State to store data • Interconnect to move data



Processors, Memories, and Networks


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Network

Processor

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Computedata

Movedata

Storedata

In computer architecture we more generally think of using • Processors for computation • Memories for storage • Networks for communication

Processor Processor

Memory Memory


What is Computer Architecture? • Design Example • Design Principles Design Methodologies

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Design Example

Design Principles

Design Methodologies



What do computer architects actually do?

Ask questionabout nature

Constructhypothesis

Test withexperiment

Analyze results anddraw conclusions

General ScienceDiscover truthsabout nature

Design and modelbaseline system

Ask questionabout system

Design and modelalternative system

Test withexperiment


Computer EngineeringExplore design space

for a new system

Build prototypeor real system



Example DesignProblem: On-ChipInterconnectionNetwork

I Intel Sandybridge EServer-Class Processor

I 435 mm2 in 32 nmtechnology with 2.27Btransistors running atseveral GHz

I Eight cores and eightmemory banks with anon-chip ring network



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How should weorganize routersand channels?

Topology

CounterClockwise

Ring

ClockwiseRing

Tile 1



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RoutingWhich path to take from

source processor todestination memory?

Tile 1

Tile 4



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Flow ControlWhich packet should

a router choose tosend to output port?



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TopologyRouting

Flow Control



Modeling in Computer Architecture

Design and modelbaseline system

Ask questionabout system

Design and modelalternative system

Test withexperiment


Computer EngineeringExplore design space

for a new system

Build prototypeor real system

// rdy is OR of the AND of reqs and grants assign in_rdy = | (reqs & grants);

reg [2:0] reqs; always @(*) begin if ( in_val ) begin

// eject packet if it is for this tile if ( dest == p_router_id ) reqs = 3'b010;

// otherwise, just pass it along ring else reqs = 3'b001;

end else begin // if !val, don't request any ports reqs = 3'b000; end end

Verilog • SystemVerilog • VHDLC++ • SystemC

Bluespec • Chisel • PyMTL



Student-Based “Model” of On-Chip Network

I Processor/Memory – Studenthands packets to appropriaterouter based on routingalgorithm; waits to receive twopackets from some other tile,and then raises hand.

I CCW/CW Network Routers –Student holds onto packets andhands them to the correctchannel; if packet for that router’stile arrives, then hand packet toprocessor/memory.

I CCW/CW Network Channels –Student walks one packet at a

time from upstream router todownstream router.

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Use Greedy Routing

Algorithm


What is Computer Architecture? Design Example • Design Principles • Design Methodologies

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Design Example

Design Principles




Design Principle: Modularity

I Decompose into components with well-defined interfaces

I A modular router design can be decomposed into a control unit and adatapath interconnected with control/status signals

Control Unit

Datapath

ControlSignals

StatusSignals

StateA

StateB



Design Principle: Hierarchy

I Recursively apply modularity principle

I A hierarchical network design can be decomposed into routers, whichis in turn decomposed into a control unit and datapath, which is in turndecomposed into queues, muxes, and registers

Control Unit

Datapath

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Design Principle: Encapsulation

I Hide implementation details frominterfaces

I An encapsulated router designcan hide the latency of the routermicroarchitecture along with anydetails related to stalls due to fullqueues or arbitration

InputPort 1

InputPort 2

InputPort 3

OutputPort 1

OutputPort 2

OutputPort 3

packetvalidready

Router



Design Principle: Regularity

I Leverage structure at variouslevels of abstraction

I A regular router design canexploit logical structure to enablea single router to be instantiatedeight times

I A regular network and routerdesign can exploit physicalstructure to simplify the chipfloorplan and layout

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Design Principle: Extensibility

I Include mechanisms/hooks tosimplify future changes

I An extensible network and routerdesign can enable easilyimplementing ring networks withvarious numbers of routers

I An extensible network and routerdesign can enable easilychanging the routing algorithm

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Design Principles in Computer Architecture

I Modularity – Decompose into components with well-defined interfaces

I Hierarchy – Recursively apply modularity principle

I Encapsulation – Hide implementation details from interfaces

I Regularity – Leverage structure at various levels of abstraction

I Extensibility – Include mechanisms/hooks to simplify future changes


What is Computer Architecture? Design Example Design Principles • Design Methodologies •

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Design Example

Design Principles




Waterfall Development Methodology

I Traditional sequentialdevelopment methodology; eachstage is completed beforebeginning the next stage

I For example, most of the designis completed before beginningthe development, and most ofthe development is completedbefore beginning testing

Discover

Design

Develop

Test

Application Requirements

Technical Design

Coding, Implementation, and Integration

Verification and Fabrication



Agile Development Methodology

I Emerging iterative developmentmethodology; move rapidlythrough all stages and theniterate back again through thestages

I For example, a component isdesigned, developed, and testedbefore moving onto anothercomponent; or a minimal yetcomplete system is designed,developed, and tested beforeincrementally adding features

Sprint#1

Discover

DesignDevelop

Test

Sprint#2

Discover

DesignDevelop

Test

Sprint#3

Discover

DesignDevelop

Test



Agile Argues for Incremental Development

X P Network

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Agile Argues for Test-Driven Development

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I Test Types. Unit tests vs. integration tests. Directed vs. random tests. Whitebox vs. blackbox tests

I Goal is to write tests firstthen implement design topass these tests

I Write tests for higher level ofabstraction, refine implementation until passes tests, add new tests

I Capture design bugs with new tests



Waterfall vs. Agile Development Methodologies

Waterfall Methodology Agile Methodology

Highly critical requirements Less critical requirements

Less experienced engineers More experienced engineers

Requirements change rarely Requirements change often

Large engineering team Small engineering team

A hybrid approach that includes aspects of both thetraditional waterfall methodology and the emergingagile methodology is an attractive option for future

hardware design projects.


What is Computer Architecture? Design Example Design Principles Design Methodologies

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Take-Away Points

I Computer engineering is an iterative processinvolving designing and modeling systems,evaluating trade-offs between various designalternatives, which in turn motivates designing andmodeling new systems

I Design principles such as modularity, hierarchy,modularity, encapsulation, regularity, andextensibility and design methodologies such aswaterfall and agile hardware development can helpmanage the significant complexity inherent inbuilding modern computing systems


What is Computer Architecture? Design Example Design Principles Design Methodologies

ECE 4750 Computer Architecturehttp://www.csl.cornell.edu/courses/ece4750

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I Part 1: Fundamental Processors – FSMprocessors; pipelined processors;structural, data, and control hazards

I Part 2: Fundamental Memories – memorytechnology; cache hierarchies; pipelined cachemicroarchitecture

I Part 3: Fundamental Networks – torus andbutterfly topologies; routing algorithms;flow control; pipelined router microarchitecture

I Part 4: Advanced Processors – superscalar execution; branch prediction;out-of-order execution; register renaming; memory disambiguation; VLIW,vector, and multithreaded processors

I Part 5: Advanced Memories – non-blocking caches; memory coherence,synchronization, consistency; memory translation, protection, virtualization


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ECE 3400 Guest Lecture Design Principles and Methodologies ...cbatten/misc/batten... · What is Computer Architecture? Design Example • Design Principles • Design Methodologies