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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 - PowerPoint PPT Presentation
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Chapter 1 - Fundamentals 1
Computer Architecture
Chapter 1
Fundamentals
Prof. Jerry Breecher
CSCI 240
Fall 2001
Chapter 1 - Fundamentals 2
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
Chapter 1 - Fundamentals 3
Art and Architecture
What’s the difference between Art and Architecture?
Lyonel Feininger,Marktkirche in Halle
Chapter 1 - Fundamentals 4
Art and Architecture
What’s the difference between Art and Architecture?
Notre Damede Paris
Chapter 1 - Fundamentals 5
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
Chapter 1 - Fundamentals 6
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!)
Chapter 1 - Fundamentals 7
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
Chapter 1 - Fundamentals 8
Technology and Computer Usage Trends
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
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.
Chapter 1 - Fundamentals 9
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
Chapter 1 - Fundamentals 10
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
Chapter 1 - Fundamentals 11
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
Chapter 1 - Fundamentals 12
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
Chapter 1 - Fundamentals 13
Measuring And Reporting Performance
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
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?
Chapter 1 - Fundamentals 14
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
Chapter 1 - Fundamentals 15
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
Chapter 1 - Fundamentals 16
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.
Chapter 1 - Fundamentals 17
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
Chapter 1 - Fundamentals 18
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
Chapter 1 - Fundamentals 19
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
Chapter 1 - Fundamentals 20
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/
Chapter 1 - Fundamentals 21
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/
Chapter 1 - Fundamentals 22
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)
Chapter 1 - Fundamentals 23
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!
Chapter 1 - Fundamentals 24
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
Chapter 1 - Fundamentals 25
Quantitative Principles of Computer Design
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
Make the common case fast.Amdahl’s Law:
Relates total speedup of a system to the speedup of some portion of that system.
Chapter 1 - Fundamentals 26
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
Chapter 1 - Fundamentals 27
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
Chapter 1 - Fundamentals 28
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
Chapter 1 - Fundamentals 29
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
Chapter 1 - Fundamentals 30
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?
Chapter 1 - Fundamentals 31
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.)
Chapter 1 - Fundamentals 32
The Concept of Memory Hierarchy
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
Fast memory is expensive.
Slow memory is cheap.
The goal is to minimize the price/performance for a particular price point.
Chapter 1 - Fundamentals 33
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
Chapter 1 - Fundamentals 34
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!)
Chapter 1 - Fundamentals 35
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.
Chapter 1 - Fundamentals 36
Wrap Up
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
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