Transcript ppt - UB Computer Science and Engineering

COMPUTER ORGANIZATION AND DESIGN
The Hardware/Software Interface
5th
Edition
January 25, 2016
Shambhu Upadhyaya (www.cse.buffalo.edu/faculty/shambhu)
lecture slides:
http://www.cse.buffalo.edu/faculty/shambhu/cse34116/
COMPUTER ORGANIZATION AND DESIGN
The Hardware/Software Interface
Copyright/Acknowledgments
The lecture material for this course has
been adapted in part from UC Berkeley,
Penn State, Publisher and Previous
Semesters of Offerings at UB
5th
Edition
Overview
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Administrative Matters (5 minutes)
Course Style, Philosophy and Structure
(15 min)
Intro to Computer Architecture (30
minutes)
Chapter 1 — Computer Abstractions and Technology — 3
Course Administration

Instructor:
Shambhu Upadhyaya ([email protected])
329 Davis Hall
Office Hours: Tuesdays 9:30 am – 11:00 am

TAs:
Hayreddin Ceker and Aleksey Charapko

Labs:
UNIX/Linux accounts for all
More info. will be provided later

Materials: http://www.cse.buffalo.edu/faculty/shambhu/cse34116

Newsgroup:
sunyab.cse.341 (may not use)

Blackboard:
UBlearns

Text:
Computer Organization and Design: The Hardware/Software
Interface, Fifth Edition, Patterson and Hennessy
Chapter 1 — Computer Abstractions and Technology — 4
Textbook purchase options


Paperback or eBook
University Bookstore on campus

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Greeks and Sneaks Bookstore, 2 blocks
from UB South campus (on Main street)


New, used, rental
Patterson Computer Org & Design, 5th Edition
Amazon
Chapter 1 — Computer Abstractions and Technology — 5
Course Exams

Reduce the pressure of taking exams

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Midterms: Friday Feb 26th, Friday March
25th, Monday May 2nd
50 minutes to take 45 minute test ( in
class)
Our goal: test knowledge vs. speed writing
All mid-terms closed book, no cheat sheets
Necessary sheets will be provided
No final exam
Chapter 1 — Computer Abstractions and Technology — 6
Course Workload

Reasonable workload (if you have good
work habits)

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No final exam: Only 3 mid-terms
Every recitation feeds into the project and
lecture
Project teams have 2-3 members (exact no.
TBD)
Science/Design units: 3 Science, 2 Design
Chapter 1 — Computer Abstractions and Technology — 7
Homework Assignments and Project

Assignments consist of two parts

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Homework assignments go out on Fridays
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Homeworks – Individual Effort: Exercises from the text book
Projects – Team Effort: Lab assignments
Assignments due in 10 days (Mondays) at beginning of
lecture
 Brief (15 minute) quiz on assignment material in lecture
or recitations (several of them)
 Must understand assignment to do quiz
 No late assignments!
Recitations will help solve problems
Homeworks will not be graded, but checked for
completeness
Solution will be posted on UBlearns
Chapter 1 — Computer Abstractions and Technology — 8
My Goal

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Show you how to understand modern computer
architecture in its rapidly changing form
Show you how to design by leading you through the
process on challenging design problems
Learn how to test things
Keep interactive
So...
 ask questions
 come to office hours
 See the TA(s)
Chapter 1 — Computer Abstractions and Technology — 9
Project/Lab Summary

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Verilog installed on Unix
SPIM available on Unix, Windows
Lab assignments
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2-3 Projects
Written report
Code submission, if necessary
Chapter 1 — Computer Abstractions and Technology — 10
Grading

Grade breakdown
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Three Midterm Exams:
(combined)
Homeworks:
Projects:
Quizzes:
55%
10%
20%
15%
No late homeworks or labs
Chapter 1 — Computer Abstractions and Technology — 11
Course Problems

Can’t make midterm

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Forgot to turn in homework … Computer/my cute dog ate
whatever …

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Tell us early and we will schedule alternate time, if appropriate
No late homeworks or labs
What is cheating?
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Common examples of cheating: running out of time on an
assignment and take from another and copy, borrow solution
“just to take a look”, peeking during exam, ...
Cheating will be met with an ‘F’ for the course
Studying together in groups is not discouraged
Work must be your own
Better off to skip an assignment (rather than copying)
But it doesn’t help on quiz (15% of grade) anyway
Chapter 1 — Computer Abstractions and Technology — 12
Project Simulates Industrial Environment

Project teams have 2-3 members in same discussion
section
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Communicate with colleagues (team members)
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Must work in groups in “the real world”
Communication problems are natural
What have you done?
What answers you need from others?
You must document your work!!!
Everyone must keep an on-line notebook
Communicate with supervisor (TAs)
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How is the team’s plan?
Short progress reports are required
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What is the team’s game plan?
What is each member’s responsibility?
Chapter 1 — Computer Abstractions and Technology — 13
The Instruction Set: a Critical Interface
software
instruction set
hardware
Chapter 1 — Computer Abstractions and Technology — 14
How Do the Pieces Fit Together?
Application
CSE 443
Compiler
Operating
System CSE 421
Firmware
Memory
Instr. Set Proc.
system CSE 241 & 341 & 490
Instruction Set
Architecture
I/O system
Datapath & Control
CSE 493 & 452
Digital Design
Circuit Design
CSE 379

Coordination of many levels of abstraction

Under a rapidly changing set of forces

Design, measurement, and evaluation
Chapter 1 — Computer Abstractions and Technology — 16
COMPUTER ORGANIZATION AND DESIGN
The Hardware/Software Interface
Chapter 1
Computer Abstractions
and Technology
5th
Edition

Progress in computer technology


Makes novel applications feasible

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Underpinned by Moore’s Law
§1.1 Introduction
The Computer Revolution
Computers in automobiles
Cell phones
Human genome project
World Wide Web
Search Engines
Computers are pervasive
Chapter 1 — Computer Abstractions and Technology — 18
Classes of Computers

Personal computers

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General purpose, variety of software
Subject to cost/performance tradeoff
Server computers

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Network based
High capacity, performance, reliability
Range from small servers to building sized
Chapter 1 — Computer Abstractions and Technology — 19
Classes of Computers

Supercomputers

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High-end scientific and engineering
calculations
Highest capability but represent a small
fraction of the overall computer market
Embedded computers

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Hidden as components of systems
Stringent power/performance/cost constraints
Chapter 1 — Computer Abstractions and Technology — 20
The PostPC Era
Chapter 1 — Computer Abstractions and Technology — 21
The PostPC Era

Personal Mobile Device (PMD)
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Battery operated
Connects to the Internet
Hundreds of dollars
Smart phones, tablets, electronic glasses
Cloud computing
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Warehouse Scale Computers (WSC)
Software as a Service (SaaS)
Portion of software run on a PMD and a
portion run in the Cloud
Amazon and Google
Chapter 1 — Computer Abstractions and Technology — 22
What You Will Learn

How programs are translated into the
machine language

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The hardware/software interface
What determines program performance

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And how the hardware executes them
And how it can be improved
How hardware designers improve
performance
What is parallel processing
Chapter 1 — Computer Abstractions and Technology — 23
Understanding Performance

Algorithm

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Programming language, compiler, architecture

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Determine number of machine instructions executed
per operation
Processor and memory system

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Determines number of operations executed
Determine how fast instructions are executed
I/O system (including OS)

Determines how fast I/O operations are executed
Chapter 1 — Computer Abstractions and Technology — 24

Design for Moore’s Law

Use abstraction to simplify design

Make the common case fast

Performance via parallelism

Performance via pipelining

Performance via prediction

Hierarchy of memories

Dependability via redundancy
§1.2 Eight Great Ideas in Computer Architecture
Eight Great Ideas
Chapter 1 — Computer Abstractions and Technology — 25
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Application software

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Written in high-level language
System software

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Compiler: translates HLL code to
machine code
Operating System: service code
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§1.3 Below Your Program
Below Your Program
Handling input/output
Managing memory and storage
Scheduling tasks & sharing resources
Hardware

Processor, memory, I/O controllers
Chapter 1 — Computer Abstractions and Technology — 26
Levels of Program Code

High-level language

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Assembly language

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Level of abstraction closer
to problem domain
Provides for productivity
and portability
Textual representation of
instructions
Hardware representation

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Binary digits (bits)
Encoded instructions and
data
Chapter 1 — Computer Abstractions and Technology — 27
The BIG Picture

Same components for
all kinds of computer

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Desktop, server,
embedded
§1.4 Under the Covers
Components of a Computer
Input/output includes

User-interface devices
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Storage devices
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Display, keyboard, mouse
Hard disk, CD/DVD, flash
Network adapters

For communicating with
other computers
Chapter 1 — Computer Abstractions and Technology — 28
Touchscreen
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PostPC device
Supersedes keyboard
and mouse
Resistive and
Capacitive types
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Most tablets, smart
phones use capacitive
Capacitive allows
multiple touches
simultaneously
Chapter 1 — Computer Abstractions and Technology — 29
Through the Looking Glass

LCD screen: picture elements (pixels)

Mirrors content of frame buffer memory
Chapter 1 — Computer Abstractions and Technology — 30
Opening the Box
Capacitive multitouch LCD screen
3.8 V, 25 Watt-hour battery
Computer board
Chapter 1 — Computer Abstractions and Technology — 31
Inside the Processor (CPU)
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Datapath: performs operations on data
Control: sequences datapath, memory, ...
Cache memory
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Small fast SRAM memory for immediate
access to data
Chapter 1 — Computer Abstractions and Technology — 32
Inside the Processor
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Apple A5
Chapter 1 — Computer Abstractions and Technology — 33
Abstractions
The BIG Picture

Abstraction helps us deal with complexity
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Instruction set architecture (ISA)
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The hardware/software interface
Application binary interface
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Hide lower-level detail
The ISA plus system software interface
Implementation
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The details underlying and interface
Chapter 1 — Computer Abstractions and Technology — 34
A Safe Place for Data
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Volatile main memory
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Loses instructions and data when power off
Non-volatile secondary memory
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Magnetic disk
Flash memory
Optical disk (CDROM, DVD)
Chapter 1 — Computer Abstractions and Technology — 35
Networks

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Communication, resource sharing,
nonlocal access
Local area network (LAN): Ethernet
Wide area network (WAN): the Internet
Wireless network: WiFi, Bluetooth
Chapter 1 — Computer Abstractions and Technology — 36

Electronics
technology
continues to evolve


Increased capacity
and performance
Reduced cost
DRAM capacity
Year
Technology
Relative performance/cost
1951
Vacuum tube
1965
Transistor
1975
Integrated circuit (IC)
1995
Very large scale IC (VLSI)
2013
Ultra large scale IC
1
35
900
2,400,000
§1.5 Technologies for Building Processors and Memory
Technology Trends
250,000,000,000
Chapter 1 — Computer Abstractions and Technology — 37
Semiconductor Technology
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Silicon: semiconductor
Add materials to transform properties:

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Conductors
Insulators
Switch
Chapter 1 — Computer Abstractions and Technology — 38
Manufacturing ICs

Yield: proportion of working dies per wafer
Chapter 1 — Computer Abstractions and Technology — 39
Intel Core i7 Wafer
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300mm wafer, 280 chips, 32nm technology
Each chip is 20.7 x 10.5 mm
Chapter 1 — Computer Abstractions and Technology — 40
Integrated Circuit Cost
Cost per wafer
Cost per die 
Dies per wafer  Yield
Dies per wafer  Wafer area Die area
1
Yield 
(1  (Defects per area  Die area/2)) 2

Nonlinear relation to area and defect rate
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Wafer cost and area are fixed
Defect rate determined by manufacturing process
Die area determined by architecture and circuit design
Chapter 1 — Computer Abstractions and Technology — 41

Which airplane has the best performance?
Boeing 777
Boeing 777
Boeing 747
Boeing 747
BAC/Sud
Concorde
BAC/Sud
Concorde
Douglas
DC-8-50
Douglas DC8-50
0
100
200
300
400
0
500
Boeing 777
Boeing 777
Boeing 747
Boeing 747
BAC/Sud
Concorde
BAC/Sud
Concorde
Douglas
DC-8-50
Douglas DC8-50
500
1000
Cruising Speed (mph)
4000
6000
8000 10000
Cruising Range (miles)
Passenger Capacity
0
2000
§1.6 Performance
Defining Performance
1500
0
100000 200000 300000 400000
Passengers x mph
Chapter 1 — Computer Abstractions and Technology — 42
Response Time and Throughput

Response time

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How long it takes to do a task
Throughput

Total work done per unit time

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How are response time and throughput affected
by

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e.g., tasks/transactions/… per hour
Replacing the processor with a faster version?
Adding more processors?
We’ll focus on response time for now…
Chapter 1 — Computer Abstractions and Technology — 43
Relative Performance
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Define Performance = 1/Execution Time
“X is n time faster than Y”
Performanc e X Performanc e Y
 Execution time Y Execution time X  n

Example: time taken to run a program

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10s on A, 15s on B
Execution TimeB / Execution TimeA
= 15s / 10s = 1.5
So A is 1.5 times faster than B
Chapter 1 — Computer Abstractions and Technology — 44
Measuring Execution Time

Elapsed time

Total response time, including all aspects

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Processing, I/O, OS overhead, idle time
Determines system performance
CPU time

Time spent processing a given job

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Discounts I/O time, other jobs’ shares
Comprises user CPU time and system CPU
time
Different programs are affected differently by
CPU and system performance
Chapter 1 — Computer Abstractions and Technology — 45
CPU Clocking

Operation of digital hardware governed by a
constant-rate clock
Clock period
Clock (cycles)
Data transfer
and computation
Update state

Clock period: duration of a clock cycle

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e.g., 250ps = 0.25ns = 250×10–12s
Clock frequency (rate): cycles per second
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e.g., 4.0GHz = 4000MHz = 4.0×109Hz
Chapter 1 — Computer Abstractions and Technology — 46
CPU Time
CPU Time  CPU Clock Cycles  Clock Cycle Time
CPU Clock Cycles

Clock Rate

Performance improved by

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
Reducing number of clock cycles
Increasing clock rate
Hardware designer must often trade off clock
rate against cycle count
Chapter 1 — Computer Abstractions and Technology — 47
CPU Time Example
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Computer A: 2GHz clock, 10s CPU time
Designing Computer B

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
Aim for 6s CPU time
Can do faster clock, but causes 1.2 × clock cycles
How fast must Computer B clock be?
Clock Cycles B 1.2  Clock Cycles A
Clock Rate B 

CPU Time B
6s
Clock Cycles A  CPU Time A  Clock Rate A
 10s  2GHz  20  109
1.2  20  109 24  109
Clock Rate B 

 4GHz
6s
6s
Chapter 1 — Computer Abstractions and Technology — 48
Instruction Count and CPI
Clock Cycles  Instructio n Count  Cycles per Instructio n
CPU Time  Instructio n Count  CPI  Clock Cycle Time
Instructio n Count  CPI

Clock Rate

Instruction Count for a program

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Determined by program, ISA and compiler
Average cycles per instruction


Determined by CPU hardware
If different instructions have different CPI

Average CPI affected by instruction mix
Chapter 1 — Computer Abstractions and Technology — 49
CPI Example


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Computer A: Cycle Time = 250ps, CPI = 2.0
Computer B: Cycle Time = 500ps, CPI = 1.2
Same ISA
Which is faster, and by how much?
CPU Time
CPU Time
A
 Instructio n Count  CPI  Cycle Time
A
A
 I  2.0  250ps  I  500ps
A is faster…
B
 Instructio n Count  CPI  Cycle Time
B
B
 I  1.2  500ps  I  600ps
B  I  600ps  1.2
CPU Time
I  500ps
A
CPU Time
…by this much
Chapter 1 — Computer Abstractions and Technology — 50
CPI in More Detail

If different instruction classes take different
numbers of cycles
n
Clock Cycles   (CPIi  Instructio n Count i )
i1

Weighted average CPI
n
Clock Cycles
Instructio n Count i 

CPI 
   CPIi 

Instructio n Count i1 
Instructio n Count 
Relative frequency
Chapter 1 — Computer Abstractions and Technology — 51
CPI Example


Alternative compiled code sequences using
instructions in classes A, B, C
Class
A
B
C
CPI for class
1
2
3
IC in sequence 1
2
1
2
IC in sequence 2
4
1
1
Sequence 1: IC = 5


Clock Cycles
= 2×1 + 1×2 + 2×3
= 10
Avg. CPI = 10/5 = 2.0

Sequence 2: IC = 6


Clock Cycles
= 4×1 + 1×2 + 1×3
=9
Avg. CPI = 9/6 = 1.5
Chapter 1 — Computer Abstractions and Technology — 52
Performance Summary
The BIG Picture
Instructio ns Clock cycles
Seconds
CPU Time 


Program
Instructio n Clock cycle

Performance depends on




Algorithm: affects IC, possibly CPI
Programming language: affects IC, CPI
Compiler: affects IC, CPI
Instruction set architecture: affects IC, CPI, Tc
Chapter 1 — Computer Abstractions and Technology — 53
§1.7 The Power Wall
Power Trends

In CMOS IC technology
Power  Capacitive load  Voltage 2  Frequency
×30
5V → 1V
×1000
Chapter 1 — Computer Abstractions and Technology — 54
Reducing Power

Suppose a new CPU has


85% of capacitive load of old CPU
15% voltage and 15% frequency reduction
Pnew Cold  0.85  (Vold  0.85) 2  Fold  0.85
4


0.85
 0.52
2
Pold
Cold  Vold  Fold

The power wall



We can’t reduce voltage further
We can’t remove more heat
How else can we improve performance?
Chapter 1 — Computer Abstractions and Technology — 55
§1.8 The Sea Change: The Switch to Multiprocessors
Uniprocessor Performance
Constrained by power, instruction-level parallelism,
memory latency
Chapter 1 — Computer Abstractions and Technology — 56
Multiprocessors

Multicore microprocessors


More than one processor per chip
Requires explicitly parallel programming

Compare with instruction level parallelism



Hardware executes multiple instructions at once
Hidden from the programmer
Hard to do



Programming for performance
Load balancing
Optimizing communication and synchronization
Chapter 1 — Computer Abstractions and Technology — 57
SPEC CPU Benchmark

Programs used to measure performance


Standard Performance Evaluation Corp (SPEC)


Supposedly typical of actual workload
Develops benchmarks for CPU, I/O, Web, …
SPEC CPU2006

Elapsed time to execute a selection of programs



Negligible I/O, so focuses on CPU performance
Normalize relative to reference machine
Summarize as geometric mean of performance ratios

CINT2006 (integer) and CFP2006 (floating-point)
n
n
Execution time ratio
i
i1
Chapter 1 — Computer Abstractions and Technology — 58
CINT2006 for Intel Core i7 920
Chapter 1 — Computer Abstractions and Technology — 59
SPEC Power Benchmark

Power consumption of server at different
workload levels


Performance: ssj_ops/sec
Power: Watts (Joules/sec)
 10
  10

Overall ssj_ops per Watt    ssj_ops i    poweri 
 i0
  i 0

Chapter 1 — Computer Abstractions and Technology — 60
SPECpower_ssj2008 for Xeon X5650
Chapter 1 — Computer Abstractions and Technology — 61

Improving an aspect of a computer and
expecting a proportional improvement in
overall performance
Taf f ected
Timprov ed 
 Tunaf f ected
improvemen t factor

Example: multiply accounts for 80s/100s


§1.10 Fallacies and Pitfalls
Pitfall: Amdahl’s Law
How much improvement in multiply performance to
get 5× overall?
80
 Can’t be done!
20 
 20
n
Corollary: make the common case fast
Chapter 1 — Computer Abstractions and Technology — 62
Fallacy: Low Power at Idle

Look back at i7 power benchmark




Google data center



At 100% load: 258W
At 50% load: 170W (66%)
At 10% load: 121W (47%)
Mostly operates at 10% – 50% load
At 100% load less than 1% of the time
Consider designing processors to make
power proportional to load
Chapter 1 — Computer Abstractions and Technology — 63
Pitfall: MIPS as a Performance Metric

MIPS: Millions of Instructions Per Second

Doesn’t account for


Differences in ISAs between computers
Differences in complexity between instructions
Instructio n count
MIPS 
Execution time  10 6
Instructio n count
Clock rate


6
Instructio n count  CPI
CPI

10
6
 10
Clock rate

CPI varies between programs on a given CPU
Chapter 1 — Computer Abstractions and Technology — 64

Cost/performance is improving


Hierarchical layers of abstraction



In both hardware and software
Instruction set architecture


Due to underlying technology development
§1.9 Concluding Remarks
Concluding Remarks
The hardware/software interface
Execution time: the best performance
measure
Power is a limiting factor

Use parallelism to improve performance
Chapter 1 — Computer Abstractions and Technology — 65