CS352H: Computer Systems Architecture

Lecture 1: What Is Computer Architecture?

August 27, 2009

University of Texas Computer Science CS352H Fall 2009 Don Fussell 1

2

Goals

Understand the “how” and “why” of computer systemorganization

Instruction set architectureSystem organization (processor, memory, I/O)Micro-architecture

Learn methods of evaluating performanceMetricsBenchmarks

Learn how to make systems go fastPipelining, cachingParallelism

Learn how to make systems less power hungry (maybe)

University of Texas Computer Science CS352H Fall 2009 Don Fussell 2

3

LogisticsLectures: TTh 3:30-5:00, WEL 3.260

Instructor: Don FussellOffice: ACES 2.120Office hours: TTh 2:00-3:00 or by appointmentEmail: fussell@cs.utexas.edu

TA: Dong LiOffice:Office Hours:Email:

Grading: Final exam 25%Midterm 20%~6 Homework + ~5 paper critiques 30%Project 25%

Homework/project late account - 3 days for the semester

Course webpage:http://www.cs.utexas.edu/~fussell/courses/cs352h

University of Texas Computer Science CS352H Fall 2009 Don Fussell 3

4

Resources

Text: Patterson & HennessyComputer Organization & Design:The Hardware/Software Interface, 4th Edition(required)

Reference : Hennessy & PattersonComputer Architecture: A Quantitative Approach(not required)

Software packagesSPIM for MIPS assemblyVerilog for class projectYou will need a CS department Unix account

Using Blackboard:Messages about the class (make sure your e-mail address iscorrect)Other resources as needed in addition to the webpageFor your own discussion groups

University of Texas Computer Science CS352H Fall 2009 Don Fussell 4

5

What is expected of you

Attend class and participatePublished lecture notes are just “notes”Remember, Powerpoint was designed for content-free industrialpresentations, there’s more here than fits into bulletsDiscussions matter – they’re the best part of the courseBe a hero – ask stupid questions, you won’t be the only one who iswondering

Do the work – the homework and project are more than halfyour grade for a reason, doing them is the heart of the courseThings aren’t always as simple as they look – the devil is in thedetails, so sweat themDon’t procrastinateTake initiative to follow up on your interestsDon’t cheat: follow code of conductwww.cs.utexas.edu/users/ear/CodeOfConduct.html

University of Texas Computer Science CS352H Fall 2009 Don Fussell 5

6

Computer Architecture

“Computer architecture, like other architecture, is the art of determiningthe needs of the user of a structure and then designing to meet thoseneeds as effectively as possible within economic and technologicalconstraints.” F.P. Brooks, Planning a Computer System, Project Stretch, 1962What does this “design” consist of?

A “programming” interface for softwareInstructionsState changes

Organizational principles for processors, memory and I/O devicesProcessors - microarchitectureOverall - system design

In order to:Meet functional and performance targetsWithin constraints, such as cost and powerWhile taking advantage of advances in technology

Architecture is about making tradeoffs

University of Texas Computer Science CS352H Fall 2009 Don Fussell 6

7

What Does a Computer Architect Do?

University of Texas Computer Science CS352H Fall 2009 Don Fussell 7

8

CS352H Topics

Technology TrendsInstruction set architectures

MIPS instruction setDesigning for performance

PipeliningInstruction level parallelism (ILP)

StaticDynamic

Memory hierarchies and cachesVirtual memoryMultiprocessors and multicoreSystem measurementSystem implementation

University of Texas Computer Science CS352H Fall 2009 Don Fussell 8

9

Application constraints

Applications drive machine balanceNumerical simulation, scientific computing, 3-d graphics/games

Floating point performanceMemory bandwidth

Transaction processing, databasesI/O throughputInteger CPU performance

Decision supportI/O bandwidth

Embedded controllersI/O timing, interfacesPower

Video processingLow precision pixel arithmetic

University of Texas Computer Science CS352H Fall 2009 Don Fussell 9

10

A Little Perspective: Processor Performance

University of Texas Computer Science CS352H Fall 2009 Don Fussell 10Taken from: Hennessy & Patterson Computer Architecture: A Quantitative Approach, 4th ed

!!!

Log scale!

1Hz = 1 cycle per second. 1GHz = 109 cycles per second

11

Technology scaling

CPUsDevice density: 2x every 1.5 years (~60%per year)Latency: 2x every 5 years (~15% per year)

Memory (DRAM)Capacity: 4x every 3 years (~60% per year)(2x every two years lately)Latency: 1.5x every 10 yearsCost per bit: decreases about 25% per year

Hard drives:Capacity: 4x every 3 years (~60% per year)Bandwidth: 2.5x every 4 yearsLatency: 2x every 5 years

Boards:Wire density: 2x every 15 years

Cables:No change

University of Texas Computer Science CS352H Fall 2009 Don Fussell 11

Machines Adapt to Changes in Technology

1970sMulti-chip CPUsSemiconductor memory is veryexpensiveMicro-coded controlComplex instruction sets

1980sSingle-chip CPUsSome on-chip RAMSimple, hard-wired controlSimple instruction setsSmall on-chip caches

1990sLots of transistorsComplex control to exploit ILPLots of on-chip memoryMulti-level caches

2000sApproaching 1B transistors!Slow wiresPower becoming expensiveMulticores

University of Texas Computer Science CS352H Fall 2009 Don Fussell 12

13

The Times They Are A-Changin'

University of Texas Computer Science CS352H Fall 2009 Don Fussell 13

1962

2001

14

What is a Computer?

Supercomputer?Web server?Game console?Desktop?Notebook?Microcontroller?

Each of these “lives” in a different space with its ownrequirements and constraintsWe need to pick one for this course

DesktopUsing the MIPS ISA

University of Texas Computer Science CS352H Fall 2009 Don Fussell 14

15

Interface Design

Interface vs. ImplementationVisibility

Three types of interfaces:Between layers

API, ISABetween modules

SCSI, PCIStandard representations

IEEE floating point, ASCII

A good interfaceLasts through several generations of implementationsIs simple – ‘economy of mechanism’ (KISS)

University of Texas Computer Science CS352H Fall 2009 Don Fussell 15

16

Instruction-Set Architecture (ISA)

University of Texas Computer Science CS352H Fall 2009 Don Fussell

HW/SW interfaceSW Impact

Support OS functionsRestartable instructionsMemory management

A good compiler targetSimpleOrthogonal

DenseHW Impact

Amenable to efficientimplementation over timeAmenable to parallelization

16

17

System-Level Organization

Design at the level ofprocessors, memories, …More important toapplication performancethan CPU designFeeds and speeds

Constrained by pincounts and signalingrates

System balanceApplication-specific

Driven byPerformance/cost goalsAvailable componentsTechnology constraints

University of Texas Computer Science CS352H Fall 2009 Don Fussell 17

Boot PROM

L2$ CC

MBus Module

MBus

L64852 MBus controlM-S Adapter

SBus

DRAM Controller

SBusDMA

SCSIEthernet

STDIOserialkbdmouseaudioRTC

FloppySBusCards

Sun SparcStation20

CPU

18

Micro-architecture

Register-transfer-level (RTL)Implement instruction setExploit technology capabilities

Locality & concurrencyIterative process

Generate architectureEstimate costEvaluate performance

Overcoming sequential natureof programs

PipeliningMultiple issueDynamic schedulingBranch prediction/speculation

University of Texas Computer Science CS352H Fall 2009 Don Fussell 18

TI SuperSPARC™ TMS390Z50

Floating-point Unit

Integer Unit

InstCache

RefMMU

DataCache

StoreBuffer

Bus Interface

19

Performance Evaluation

What’s the right measure?Instruction count? cache b/w? I/O throughput?Application response time? Application throughput?

Measure what?Benchmarks? Real applications? Traces?

Measure how?Simulation? Math models? Real tests?

University of Texas Computer Science CS352H Fall 2009 Don Fussell 19

20

Major Components of a Computer

Desktop design targetProcessor: 25% of costMemory: 25% of costRest (I/O devices, power supply, enclosure): 50%

University of Texas Computer Science CS352H Fall 2009 Don Fussell 20

Processor

Control

Datapath

Memory

Devices

Input

Output

Network

21

PC Chassis

University of Texas Computer Science CS352H Fall 2009 Don Fussell 21

22

Motherboard organization

University of Texas Computer Science CS352H Fall 2009 Don Fussell 22

Mac mini

23

PC Motherboard

University of Texas Computer Science CS352H Fall 2009 Don Fussell 23

University of Texas Computer Science CS352H Fall 2009 Don Fussell 24

Pentium 4 Chip

25

Summary

Architecture: Structure of “things”Interplay between technology and architectureComputer architect uses quantitative methods to:

Design interfacesDevelop machine organization: system-level & micro-architecture

This course:Instruction-Set Architectures (ISAs)Performance evaluation (a tiny bit)PipeliningMemorySystem organizationParallelismPower

University of Texas Computer Science CS352H Fall 2009 Don Fussell 25

26

First Assignment

Read the Moore paper (see webpage)Write a one page critique

Typewritten, font size 10-12Critique format

Headline message: a one sentence tag line for the paperElevator pitch: a one paragraph summary of the paper’s keymessagesA couple of paragraphs to support and analyze the elevator pitch

Hand in your one page review at the beginning of next classYou should use this format for all other papers as well

University of Texas Computer Science CS352H Fall 2009 Don Fussell 26

27

Next Time

Hand in a hard copy of your one-page typewritten review of theMoore paper at the beginning of the classWe’ll discuss the paperThen, instruction set architectures, specifically the MIPS ISARead Chap 1 for backgroundRead Chap 2.1-2.10 for class prep

University of Texas Computer Science CS352H Fall 2009 Don Fussell 27