Chapter 1 - Fundamentals1 Computer Architecture Chapter 1 Fundamentals Prof. Jerry Breecher CSCI 240 Fall 2001

Chapter 1 - Fundamentals 1

Computer Architecture

Chapter 1

Fundamentals

Prof. Jerry Breecher

CSCI 240

Fall 2001


Introduction

1.1 Introduction

1.2 The Task of a Computer Designer

1.3 Technology and Computer Usage Trends

1.4 Cost and Trends in Cost

1.5 Measuring and Reporting Performance

1.6 Quantitative Principles of Computer Design

1.7 Putting It All Together: The Concept of Memory Hierarchy


Art and Architecture

What’s the difference between Art and Architecture?

Lyonel Feininger,Marktkirche in Halle


Art and Architecture

What’s the difference between Art and Architecture?

Notre Damede Paris


What’s Computer Architecture?

The attributes of a [computing] system as seen by the programmer, i.e., the conceptual structure and functional behavior, as distinct from the organization of the data flows and controls the logic design, and the physical implementation.

Amdahl, Blaaw, and Brooks, 1964

SOFTWARESOFTWARE


What’s Computer Architecture?

• 1950s to 1960s: Computer Architecture Course Computer Arithmetic.

• 1970s to mid 1980s: Computer Architecture Course Instruction Set Design, especially ISA appropriate for compilers. (What we’ll do in Chapter 2)

• 1990s to 2000s: Computer Architecture CourseDesign of CPU, memory system, I/O system, Multiprocessors. (All evolving at a tremendous rate!)


The Task of a Computer Designer

1.1 Introduction 1.2 The Task of a Computer

Designer 1.3 Technology and Computer

Usage Trends 1.4 Cost and Trends in Cost 1.5 Measuring and Reporting

Performance 1.6 Quantitative Principles of

Computer Design 1.7 Putting It All Together: The

Concept of Memory Hierarchy

Evaluate ExistingEvaluate ExistingSystems for Systems for BottlenecksBottlenecks

Simulate NewSimulate NewDesigns andDesigns and

OrganizationsOrganizations

Implement NextImplement NextGeneration SystemGeneration System

TechnologyTrends

Benchmarks

Workloads

ImplementationComplexity


Technology and Computer Usage Trends

1.1 Introduction







Similarly, Computer Architecture is about working within constraints:

• What will the market buy?

• Cost/Performance

• Tradeoffs in materials and processes

When building a Cathedral numerous very practical considerations need to be taken into account:

• available materials

• worker skills

• willingness of the client to pay the price.


TrendsGordon Moore (Founder of Intel) observed in 1965 that the number of

transistors that could be crammed on a chip doubles every year.

This has CONTINUED to be true since then.Transistors Per Chip

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1970 1975 1980 1985 1990 1995 2000 2005

4004

Power PC 601486

386

80286

8086

Pentium

Pentium Pro

Pentium II

Power PC G3

Pentium 3


TrendsProcessor performance, as measured by the SPEC benchmark has

also risen dramatically.

0

1000

2000

3000

4000

50008

7

88

89

90

91

92

93

94

95

96

97

98

99

20

00

DEC Alpha 21264/600

DEC Alpha 5/500

DEC Alpha 4/266

DEC AXP/500

Sun-4/

260

IBMRS/

6000

MIPS M

2000

Alpha 6/833


TrendsMemory Capacity (and Cost) have changed dramatically in the last

20 years.

size

Year

Bits

1000

10000

100000

1000000

10000000

100000000

1000000000

1970 1975 1980 1985 1990 1995 2000

year size(Mb) cyc time

1980 0.0625 250 ns

1983 0.25 220 ns

1986 1 190 ns

1989 4 165 ns

1992 16 145 ns

1996 64 120 ns

2000 256 100 ns


TrendsBased on SPEED, the CPU has increased dramatically, but memory

and disk have increased only a little. This has led to dramatic changed in architecture, Operating Systems, and Programming practices.

Capacity Speed (latency)

Logic 2x in 3 years 2x in 3 years

DRAM 4x in 3 years 2x in 10 years

Disk 4x in 3 years 2x in 10 years


Measuring And Reporting Performance

1.1 Introduction







This section talks about:

1. Metrics – how do we describe in a numerical way the performance of a computer?

2. What tools do we use to find those metrics?


Metrics

• Time to run the task (ExTime)– Execution time, response time, latency

• Tasks per day, hour, week, sec, ns … (Performance)

– Throughput, bandwidth

Plane

Boeing 747

BAD/Sud Concodre

Speed

610 mph

1350 mph

DC to Paris

6.5 hours

3 hours

Passengers

470

132

Throughput (pmph)

286,700

178,200


Metrics - Comparisons

"X is n times faster than Y" means

ExTime(Y) Performance(X)

--------- = ---------------

ExTime(X) Performance(Y)

Speed of Concorde vs. Boeing 747

Throughput of Boeing 747 vs. Concorde


Metrics - ComparisonsPat has developed a new product, "rabbit" about which she wishes to determine

performance. There is special interest in comparing the new product, rabbit to the old product, turtle, since the product was rewritten for performance reasons. (Pat had used Performance Engineering techniques and thus knew that rabbit was "about twice as fast" as turtle.) The measurements showed:

Performance Comparisons

Product Transactions / second Seconds/ transaction Seconds to process transaction

Turtle 30 0.0333 3

Rabbit 60 0.0166 1

Which of the following statements reflect the performance comparison of rabbit and turtle?

o Rabbit is 100% faster than turtle.o Rabbit is twice as fast as turtle.o Rabbit takes 1/2 as long as turtle.o Rabbit takes 1/3 as long as turtle.o Rabbit takes 100% less time than turtle.

o Rabbit takes 200% less time than turtle.o Turtle is 50% as fast as rabbit.o Turtle is 50% slower than rabbit.o Turtle takes 200% longer than rabbit.o Turtle takes 300% longer than rabbit.


Metrics - Throughput

Compiler

Programming Language

Application

DatapathControl

Transistors Wires Pins

ISA

Function Units

(millions) of Instructions per second: MIPS(millions) of (FP) operations per second: MFLOP/s

Cycles per second (clock rate)

Megabytes per second

Answers per monthOperations per second


Methods For Predicting Performance

• Benchmarks, Traces, Mixes• Hardware: Cost, delay, area, power estimation• Simulation (many levels)

– ISA, RT, Gate, Circuit• Queuing Theory• Rules of Thumb• Fundamental “Laws”/Principles


Benchmarks

• First Round 1989– 10 programs yielding a single number (“SPECmarks”)

• Second Round 1992– SPECInt92 (6 integer programs) and SPECfp92 (14 floating point programs)

• Compiler Flags unlimited. March 93 of DEC 4000 Model 610:

spice: unix.c:/def=(sysv,has_bcopy,”bcopy(a,b,c)=memcpy(b,a,c)”

wave5: /ali=(all,dcom=nat)/ag=a/ur=4/ur=200

nasa7: /norecu/ag=a/ur=4/ur2=200/lc=blas• Third Round 1995

– new set of programs: SPECint95 (8 integer programs) and SPECfp95 (10 floating point)

– “benchmarks useful for 3 years”– Single flag setting for all programs: SPECint_base95, SPECfp_base95

SPEC: System Performance Evaluation Cooperative


BenchmarksCINT2000 (Integer Component of SPEC CPU2000):

Program Language What Is It164.gzip C Compression

175.vpr C FPGA Circuit Placement and Routing

176.gcc C C Programming Language Compiler

181.mcf C Combinatorial Optimization

186.crafty C Game Playing: Chess

197.parser C Word Processing

252.eon C++ Computer Visualization

253.perlbmk C PERL Programming Language

254.gap C Group Theory, Interpreter

255.vortex C Object-oriented Database

256.bzip2 C Compression

300.twolf C Place and Route Simulator

http://www.spec.org/osg/cpu2000/CINT2000/


BenchmarksCFP2000 (Floating Point Component of SPEC

CPU2000):Program Language What Is It168.wupwiseFortran 77 Physics / Quantum Chromodynamics171.swim Fortran 77 Shallow Water Modeling172.mgrid Fortran 77 Multi-grid Solver: 3D Potential Field173.applu Fortran 77 Parabolic / Elliptic Differential Equations177.mesa C 3-D Graphics Library178.galgel Fortran 90 Computational Fluid Dynamics179.art C Image Recognition / Neural Networks183.equake C Seismic Wave Propagation Simulation187.facerec Fortran 90 Image Processing: Face Recognition188.ammp C Computational Chemistry189.lucas Fortran 90 Number Theory / Primality Testing191.fma3d Fortran 90 Finite-element Crash Simulation 200.sixtrack Fortran 77 High Energy Physics Accelerator Design 301.apsi Fortran 77 Meteorology: Pollutant Distribution

http://www.spec.org/osg/cpu2000/CFP2000/


Benchmarks Sample Results For SpecINT2000

Base Base Base Peak Peak Peak

Benchmarks Ref Time Run Time Ratio Ref Time Run Time Ratio

164.gzip 1400 277 505* 1400 270 518*

175.vpr 1400 419 334* 1400 417 336*

176.gcc 1100 275 399* 1100 272 405*

181.mcf 1800 621 290* 1800 619 291*

186.crafty 1000 191 522* 1000 191 523*

197.parser 1800 500 360* 1800 499 361*

252.eon 1300 267 486* 1300 267 486*

253.perlbmk 1800 302 596* 1800 302 596*

254.gap 1100 249 442* 1100 248 443*

255.vortex 1900 268 710* 1900 264 719*

256.bzip2 1500 389 386* 1500 375 400*

300.twolf 3000 784 382* 3000 776 387*

SPECint_base2000 438

SPECint2000 442

http://www.spec.org/osg/cpu2000/results/res2000q3/cpu2000-20000718-00168.asc

Intel OR840(1 GHz Pentium III processor)


BenchmarksPerformance Evaluation

• “For better or worse, benchmarks shape a field”• Good products created when have:

– Good benchmarks– Good ways to summarize performance

• Given sales is a function in part of performance relative to competition, investment in improving product as reported by performance summary

• If benchmarks/summary inadequate, then choose between improving product for real programs vs. improving product to get more sales;Sales almost always wins!

• Execution time is the measure of computer performance!


Benchmarks

Management would like to have one number.

Technical people want more:

1. They want to have evidence of reproducibility – there should be enough information so that you or someone else can repeat the experiment.

2. There should be consistency when doing the measurements multiple times.

How to Summarize Performance

How would you report these results?

Computer A Computer B Computer C

Program P1 (secs) 1 10 20

Program P2 (secs) 1000 100 20

Total Time (secs) 1001 110 40


Quantitative Principles of Computer Design

1.1 Introduction







Make the common case fast.Amdahl’s Law:

Relates total speedup of a system to the speedup of some portion of that system.


Amdahl's Law

Suppose that enhancement E accelerates a fraction F of the task by a factor S, and the remainder of the task is unaffected

Quantitative Design

tEnhancemenWithoutePerformanc

tEnhancemenWithePerformanc

tEnhancemenWithTimeExecution

tEnhancemenWithoutTimeExecutionESpeedup

__

__

___

___)(

Speedup due to enhancement E:

This fraction enhanced


ExTimenew = ExTimeold x (1 - Fractionenhanced) + Fractionenhanced

Speedupoverall =ExTimeold

ExTimenew

Speedupenhanced

=

1

(1 - Fractionenhanced) + Fractionenhanced

Speedupenhanced

Quantitative Design

This fraction enhanced

ExTimeold ExTimenew

Amdahl's Law


Amdahl's Law

• Floating point instructions improved to run 2X; but only 10% of actual instructions are FP

Speedupoverall = 1

0.95= 1.053

ExTimenew = ExTimeold x (0.9 + .1/2) = 0.95 x ExTimeold

Quantitative Design


Quantitative Design

“Instruction Frequency”

Invest Resources where time is Spent!

CPI = (CPU Time * Clock Rate) / Instruction Count = Cycles / Instruction Count

n

iii ICPITimeCycleTimeCPU

1

**__

n

iii FCPICPI

1

* whereCountnInstructio

Ii

iF _

Number of instructions of type I.

Cycles Per Instruction


Quantitative Design

Base Machine (Reg / Reg)

Op Freq Cycles CPI(i) (% Time)

ALU 50% 1 .5 (33%)

Load 20% 2 .4 (27%)

Store 10% 2 .2 (13%)

Branch 20% 2 .4 (27%)

Total CPI 1.5

Suppose we have a machine where we can count the frequency with which instructions are executed. We also know how many cycles it takes for each instruction type.

Cycles Per Instruction

How do we get CPI(I)?How do we get %time?


Quantitative Design

Locality of Reference

Programs access a relatively small portion of the address space at any instant of time.

There are two different types of locality:

Temporal Locality (locality in time): If an item is referenced, it will tend to be referenced again soon (loops, reuse, etc.)

Spatial Locality (locality in space/location): If an item is referenced, items whose addresses are close by tend to be referenced soon (straight line code, array access, etc.)


The Concept of Memory Hierarchy

1.1 Introduction







Fast memory is expensive.

Slow memory is cheap.

The goal is to minimize the price/performance for a particular price point.


Memory Hierarchy

RegistersLevel 1 cache

Level 2Cache

Memory Disk

Typical Size

4 - 64 <16K bytes <2 Mbytes <16 Gigabytes

> 5 Gigabytes

Access Time

1 nsec 3 nsec 15 nsec 150 nsec 5,000,000 nsec

Bandwidth (in MB/sec)

10,000 – 50,000

2000 - 5000 500 - 1000 500 - 1000 100

Managed By

Compiler Hardware Hardware OS OS/User


Memory Hierarchy

• Hit: data appears in some block in the upper level (example: Block X)

– Hit Rate: the fraction of memory access found in the upper level– Hit Time: Time to access the upper level which consists of

RAM access time + Time to determine hit/miss• Miss: data needs to be retrieve from a block in the lower level

(Block Y)– Miss Rate = 1 - (Hit Rate)– Miss Penalty: Time to replace a block in the upper level +

Time to deliver the block the processor• Hit Time << Miss Penalty (500 instructions on 21264!)


Memory Hierarchy

RegistersLevel 1 cache

Level 2Cache

Memory Disk

What is the cost of executing a program if:• Stores are free (there’s a write pipe)• Loads are 20% of all instructions• 80% of loads hit (are found) in the Level 1 cache• 97 of loads hit in the Level 2 cache.


Wrap Up

1.1 Introduction







Documents

Chapter 1 - Fundamentals1 Computer Architecture Chapter 1 Fundamentals Prof. Jerry Breecher CSCI 240 Fall 2001