ECE437: Introduction to Digital Computer Design and Prototyping
Instructor: T. N. Vijaykumar
Ch 1a (Intro)
Spring 2021
Course administration: via Brightspace
Acknowledgements and Disclaimer
• Many slides are adapted and extended from multiple sources
– Publisher resources
– Profs. Thottethodi, Pai, and Patterson
– Copyright message applies only to additions/extensions
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Performance of Computers
• What do these two intervals have in common?
– 1971 – 2018 (48 years) – 2019 – 2020 (2 years)
– 1971 – first microprocessor
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Performance of Computers
• 2x faster every 18 months (exponential trend: 2n faster after 18n months)
• 2x means double although the intervals are different in length, absolute speed improvements of computers similar in the intervals!
• The amount of improvement in 48 years (1971 -2018) is repeated in just 2 years (2019-2020)!
• Bottomline: Computer architects rule!
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Ubiquity of Computers
• Originally used by governments for military applications
– a few handful in number
• Now used by people for all kinds of things
– business, entertainment, engineering, science, …
– visible and invisible – billions in number
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So what?
• Higher performance leads to
– Better utilization of all those billions (and more) computers
– enable applications previously infeasible
• ECE437 will teach you FOUR pillars of modern computer systems – pipelining, caches, coherence, and virtual memory
– UNIVERSAL ideas hardware AND software
• Many students get (software) jobs based on 437
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Outline
• Administrivia
• Very brief introduction
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Instructor
• Instructor: Prof. T. N. Vijaykumar
– 320EEBuilding,4940592,vijay@ecn.purdue.edu
– Admin. Assistant: Mary Ann Satterfield, EE325
– Office hours: Mon Tues 4:30-5:30 (online, email me to schedule)
• LectureTA:VaibhavRamachandran – ramachav@ecn.purdue.edu
– SeeBrSforofficehours
• Textbook
– ComputerOrganizationandDesign-H/WS/Winterface,
Hennessy and Patterson
– Fifth Edition (MIPS) – DIFFERENT from other editions –
the exercises are different
– You should get “5th Ed. MIPS” else you will get zero on
homeworks
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Lectures
• I like my classes to be highly interactive
• Please ask if something is not clear
– DO NOT be intimidated
• No question is stupid or trivial
• No confusion is small or unimportant
• Don’t think everybody else gets it except you – probably some others don’t get it too
• The course builds on itself so ask right away else you will not get later chapters
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Lectures
• If you come to class, your work will reduce by 10x than trying to learn on your own
– Engage/understand/internalize IN the lectures – NOT “go back to slides later” – INEFFECTIVE
• If there is an issue with the lab, lectures, homeworks, or exams please do tell me
– I usually know and avoid problems but sometimes I may be unaware
– Lab and lectures are VERY carefully synchronized so lecture is ahead
– Lab TAs and I meet every week (+ many emails)
• I want to make sure you learn 437 very well
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My personal goal
• Computer architecture (437) is my craft
• I looove this stuff!
• I want you to learn my craft well enough that many of you will choose to build a career on it for the rest of your lives
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Online lectures
• Online vs. in-person is far less important than attending lectures
• If lectures are in-person but you don’t attend then 437 will be hard
• If online lectures and you stay engaged, internalize, and ask questions (yes, online) then you will learn a lot in 437
• I dislike online but the virus is deadly
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Online lectures
• Still, online may pose some difficulties
• I will try very hard to ensure every one of you learns 437 really really well
• To offset online difficulties, I will do extra things usually not done
– Eg If needed, I will hold one-on-one online meetings (< 5 minutes) every 1-2 weeks to ensure you are following the material
– I will hold extra office hours for those that need help
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Tips for lab
• Start EARLY – MOST important
– If you start the day before, you won’t finish
– Start the next lab IMMEDIATELY after previous
• Testing and debugging efficiently
– If your debugging is poor, you will spend 20 hours on a bug that should take 20 minutes
– Lab will become impossible
– Spending 40+ hours/lab is NOT a matter of pride –
it shows poor coding, testing, and debugging skills • Every lab code is used in later labs
– so bugs in early labs will show up later and make your life miserable
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Tips for lab
• Very hard to find the bugs from 2 months ago
– Very hard to even realize that lab 4 code is broken when your lab 8 code does not run
• How do we combat this?
– Start EARLY
– THOROUGHLY test code for EACH lab – write MANY MANY tests for EACH lab – WELL beyond the few tests we give you – Beat up your design for EACH lab
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Administration
• Communication/Administration: Brightspace (BrS)
– Questions on lectures, labs, homeworks, solutions
– Important announcements
– Grades
– Anonymous rants discussion board
• Confidential and/or individual correspondence -- email
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ABET Course Objectives (Outcomes)
• Informallystatedhere
– Formal outcome statements on Brightspace
• Threeoutcomesassessedinthelecture – Computer Arithmetic
– Single-cycle processor + cache
– Pipelined processor + cache
• Oneinthelab
– Suboutcomestosatisfytheonemajorlaboutcome
• Lectureoutcomes:
– Mastery questions in Homeworks/Midterms
– Remediation question
– Ifclosebutnotquitethere,theremaybeverbalremediation
• Has never happened before
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Homeworks
• You can VERBALLY discuss BEFORE you write the FIRST word for ANY problem in a homework
– You can talk about how to approach a problem and ideas for solution
– No discussions after you start writing – No exchange of anything written EVER
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Grading
– 10% homework+1-minute quizzes, 30% midterms (2), 20% final, 40% lab
– Part of homework grade will be used to incentivize • Attendance at visitor talks
• Course feedback
– Curve based, plus/minus (cluster driven)
– Historical grade distribution
• 20-25% A’s, 25-30% B’s, 30-40% C’s, 5-10% D’s
• Percentages NOT meant as guide for this offering • Plus/minus grading will be used
– Guaranteed F’s : Failure to satisfy outcomes despite multiple opportunities, absence from exams/labs
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• Grading
One-minute quizzes
• One-minute quiz on previous lecture
• Typically one-word or one-phrase answer
• START of EVERY lecture
– 8:30-8:31 am
– Submit on Brightspace
– Be ready with “Quizzes” in 437 on Brightspace at
the start of every lecture
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Cheating
• Don’t even think about it
• Grave consequences beyond failing the class and permanent record
• Senior-year class so failing means – Graduation delayed
– Extra tuition/room/board costs
– Any lined-up job lost
– Lifeplansruined(outofsyncwithsignificantother’splans) – Lifemessedupirreparably
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Outline Fall
•Mostly accurate
• Important Weeks
•Midterms (tentative) • Breaks
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Week
1
2
3
4
5
6
7
8
9
12
13
14
15
16
Lectures
Ch 1a (intro), 2
Ch. 4a (single cycle)
Ch. 4a, 1b (performance)
Ch. 4b (pipeline)
Ch 4b
Ch. 4b, 5a (cache)
Ch. 5a, Midterm1?
Oct Break M-T, ch 6 (multicore), Midterm1?
Ch 6
Ch 5b (virtual mem)
Ch 3b (FP ALU) Midterm2?
Midterm2? Ch 3b
Thanksgiving W-F
Ch (I/O)
Lab
Tutorial, Reg File, ALU
ISA
Mem Arbiter
Single cycle
Pipeline
Pipeline
Pipeline
Midterm report
Cache
10
11
Ch 6
Ch 3a (Int ALU)
Cache
Multicore
Multicore
Multicore s/w
Multicore
Thanksgiving
Final report
Outline Spring
•Mostly accurate
• Important Weeks
•Midterms (tentative) • Breaks
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Week
1
2
3
4
5
6
7
8
9
12
13
14
15
16
Lectures
Ch 1a (intro), 2
Ch. 4a (single cycle)
Ch. 4a, 1b (performance)
Ch. 4b (pipeline)
Ch 4b
Ch. 4b, 5a (cache)
Ch. 5a, Midterm1?
Ch. 6 (multicore), Midterm1?
Ch. 6
Ch 3a (Int ALU)
Ch 5b (virtual mem), Midterm2?
Ch 3b (FP ALU) Midterm2?
Ch 3b
Ch (I/O)
Lab
Tutorial, Reg File, ALU
ISA
Mem Arbiter
Single cycle
Pipeline
Pipeline
Pipeline
Midterm report
Cache
10
11
Spring Break
Ch 6
Cache
Multicore
Multicore
Multicore s/w
Multicore
Final report
Introduction of ECE437
• ECE270 - Transistors up to multiplexors
• ECE362 - Assembly Language to Instruction Set Architecture
• ECE337 – Verilog, ASIC design
• ECE437 - Puts the three together
– great with ECE468 (compilers), ECE469 (OS)
– if you are interested in hardware, you MUST do
software!
• Requires managing complexity through
ABSTRACTION
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Why Study Computer Design
• To design new computers: old designs become obsolete fast
• To be an informed user
– a little auto mechanics helps owner infrequently, but importantly
• To learn to deal with complexity via abstraction
– problems that take months and years to complete
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Why don’t old designs suffice? • (R)evolutionintechnology“Technologypush”
1947
1st transistor
Bell Labs
1958
1st integrated circuit
Texas Instruments
1971
1st microprocessor Intel 4004
2300 transistors, 108 kHz
1978
Intel 8086
29K Transistors
1989
Intel 80486
1.2M Transistors
1995
Intel Pentium Pro
5.5M Transistors
2003
Intel Pentium 4
125M Transistors
2007
QuadCore Xeon
820M Transistors
2010
8-core Nehalem-EX
2.3B transistors
2014
15-core Xeon Ivy Bridge-Ex
4.3B transistors
2017
22-core Xeon Broadwell-E5
7.2B - lead feature Turbo Boost Max 3.0 created by my PhD grad Mike Powell
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Why don’t old designs suffice?
• Applications change“Application pull” – Missile trajectories
– Payroll processing
– Spread sheets
– Desktop publishing
– Collaborative computing, Internet – Games
– Facebook, Twitter, Web Search
• Next “killer app”? Machine learning?
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Why don’t old designs suffice?
• Architecture matches what software wants with what hardware can support – Technology pusharchapplication pull
• It’s not just about scale
– More hardware, larger software
• New constraints
– Power: Server-with-built-in-skillet?
– Faults: What if one bit out of a billion flips randomly?
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How to deal with complexity
• Through abstraction
• Black boxes
• Difference between interface and implementation
– Interface - WHAT something does – Implementation - HOW it does so
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• 2-to-1 Mux • Interface:
S
X Y
O
Abstraction - Example
S=0? O=X : O=Y
• Implementations
– gates (fast or slow), pass transistors
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What’s the Big Deal?
• A real processor’s interface specification – Huge volumes
• Worse for full computers, in general - a tower of abstraction
– Application software
– System software (OS and
compiler/assembler/linker)
– Hardware (CPU, memory, I/O)
• Each interface is complex and implemented with layer(s) below
– Abstraction keeps unnecessary details hidden
• Thousands of engineers to build one product
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Modern computer systems
Application software
System software (compiler,OS,network,security)
Architecture (CPU, memory, I/O, network)
Circuits (electrical, magnetic, photonic, bio/chemical, quantum)
Transistors, wires, antenna
Physics, chemistry, biology, math
Universe of application domains
computer science/engineering (they are the same – local differences in individual schools irrelevant, arbitrary, historical)
electrical engineering
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Basic Division of Hardware
• In space and time – In space
CPU
Output
Input
Control
Memory
Datapath
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Basic Division of Hardware
• Intime
– Fetchtheinstructionfrommemory addr1,r2,r3 – Decodetheinstruction-whatdoesthismean?
– Read input operands
– Perform operation
– Writeresults
– Determinenextinstruction
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read r2, r3 add writetor1 pc:=pc+4
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Recap
• Dealing with complexity – Abstraction
• Machine independent HLL – Variables, operations
• Compiler/Assembler/linker
– Machine (interface) dependent instructions – Implementation independent (backward
compatibility) • Hardware
– Instructions
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One-minute quiz
Fill in the blanks
• Abstraction separates __________ from ___________
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Latency vs. Throughput
• Better uniprocessor (twice as fast)
– 2x latency improvement = 2x throughput improvement
• Multicore
– 2x throughput improvement
– Each task takes the same amount of time same latency
– Can we make each task faster -- lower latency?
• Again: Why multicore?
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Multicores
• We cannot make the clock any faster because power will blow up
• 4 cores can give better performance at less power than a 4-times faster clock
• But multicores need parallel programming (break one program into many threads) which is MUCH harder than sequential programming – BIG issue
– cannot be programmed cannot be sold!
• More in Chapter 6
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Chapter order in lectures
• To stay ahead of the lab, I will follow: Chapters 1a, 2, 4a, 1b, 4b, 5a, 5b/6, 3a, 5c, I/O, 3b
– Maintains logical flow of the material
– Ch. 4a+b, 5a, and 6 are needed early for the lab, so we cover them early
• For now, remember that performance means time to execute a program
– More details later (ch. 1b, 1.6 onwards)
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Conclusion
• Designers must know BOTH software and hardware
– Compilers, Operating Systems, Networks, Security
• Both contribute to layers of abstraction of
computers
• Read the book - ~25 pages of Chapter 1 done!!
– 1.1-1.4 done
• Through the course, read the book
(preferably BEFORE lecture, or at least after lecture)
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