Chapter 1. Fundamentals of Computer Design

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Chapter 1. Fundamentals of Computer Design

• Introduction
• Performance Improvement due to
• (1). Advances in the technology
• (2). Innovation in computer design
• 1945-1970 (1) and (2) made a major contribution
  to performance improvement
• 1970 25 to 30 per year performance
  improvement for the mainframes and minicomputers.
• 1975 35 per year performance improvement for
  microprocessors simply due to (1).

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Performance Growth for Micro-processors
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Changes in the Marketplaces Made a Successful
Architecture

• The virtual elimination of assembly language
  reduced the need for object code compatibility
• The creation of standardized, vendor-independent
  operating system, such as Unix and Linux, lowered
  the cost and risk
• Consequence of the changes
• Enable the development of RISCs to focus on
• Exploitation of instruction level parallelism
• Use of caches
• Lead to 50 increase in performance per year

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The Effect of the Growth rate in Computer
Performance

• Significantly enhanced the capability available
  to computer users
• Lead to the dominance of microprocessor-based
  computers across the entire range of computer
  design.
• Workstations and PCs have emerged as major
  products.
• Servers replace minicomputers.
• Multiprocessors replace mainframe computers and
  super computers.
• The advance of IC technology
• Emergence of RSIC
• Renewal of CISC such as x86 (IA32)
  microprocessors.

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The Changing Face of Computing

• 1960s Large mainframes
• Business data processing and scientific computing
• 1970s Minicomputers
• Time-sharing
• 1980s Desktop computing(personal computing)
• 1990s Internet and Word Wide Web (servers)
• 2000s Embedded computing, mobile computing,
  and pervasive computing

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Tasks of a Computer Designer

• Determine what attributes are important for a new
  machine, then design a machine to maximize
  performance while staying within cost
  constraints.
• Task aspects Instruction set design, functional
  organization, logic design, and implementation.
• In the past, Computer Architecture often
  referred only to instruction set design. Other
  aspects of computer design were called
  implementation.
• In this book, Computer Architecture is intended
  to cover all three aspects of computer design
  instruction set architecture, organization and
  hardware.
• Instruction set architecture refers to the
  actual programmable-visible instruction set. It
  serves as the boundary between the hardware and
  software.

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• organization includes the high-level aspects of
  a computers design, such as the memory system,
  the bus structure, and the internal CPU.
• NEC VR5432 and NEC VR 4122 have the same
  instruction set architecture but with different
  organization.
• Hardware would include the detailed logic
  design and packaging technology of the machine.
• For example different Pentium microprocessors
  running in different frequency have the same
  instruction set architecture and organization but
  with different hardware implementation
• Organization and hardware are two components of
  implementations.

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Functional Requirements (Fig. 1.4)

• Application Area
• General purpose, scientific and server,
  commercial, embedded computing
• Level of Software Compatibility
• At programming language, object code or binary
  code compatibility
• Operating System Requirements
• Size of address space, memory management,
  protection
• Standards
• Floating point, I/O bus, operating systems,
  networks, programming languages

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Technology Trends

• A successful instruction set architecture must be
  designed to survive changes in computer
  implementation technology.
• Trends in implementation technology
• Integrated circuit logic technology
• Transistor density 35 increase per year,
  quadruple in 4 years.
• Die size 1020 increase per year
• Transistor count/per chip 55 increase per year.
• Transistor speed scales more slowly.
• DRAM
• Density 4060 increase per year recently.
• Cycle time decrease 1/3 in 10 years.
• Magnetic disk
• Density 100 increase per year recently.
• 30 increase per year, double in 3 years,
  prior to 1990.
• Network technology
• Ethernet 10M to 100M to 1G byte band width.

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Scaling of IC Technology

• IC Process Technology
• 10um(1971) 0.18um(2001)
• IC Technology and Computer Performance
• Transistor performance
• Wire delay
• Power consumption

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Cost, Price and Their Trends

• Cost reduction factors
• Learning curve drives the cost down
  manufacturing costs over time, i.e., yield
  improvement.
• High volume (i.e. mass production)
• Commodities are products sold by multiple vendors
  in large volumes and essentially identical, i.e.,
  competition.
• Price of DRAM (fig. 1.5)
• Price of Pentium III (fig. 1.6)
• Cost of an integrated circuit
• Cost of die f(die area)
• Computer designer affects die size both by what
  functions are included on the die and by the
  number of I/O pins.
• Distribution of cost in a system (fig. 1.9, 1.10)

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Prices of DRAM
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Price of Pentium III
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Price for 1000 PC
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Measuring and Reporting Performance

• X is n times faster than Y means
• The term system performance is used to refer to
  elapsed time on an unloaded system.
• CPU performance refers to user CPU time on an
  unloaded system.
• To evaluate a new system is to compare the
  execution time of her workload - the mixture of
  programs and operating system commands run on a
  machine.

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Choosing Programs to Evaluate Performance

• Best case Measure the execution time of a
  systems workload
• General case five levels of programs are used
• Real programs C compiler, Tex, Spice, etc.
• Modified (scripted) applications A collection of
  real applications
• Kernels small, key pieces from the real
  programs, ex., Livermore loops and Linpack.
• Toy Benchmarks 10 to 100 lines of code and
  produce a result the user already knows, ex.,
  puzzle, quicksort,
• Synthetic benchmarks try to match the average
  frequency of operations and operands of a large
  set of programs, ex., Whetstone and Drystone.
• Performance prediction accuracy
• Real programs is best, wile synthetic benchmarks
  is worst. and reporting performance results (fig.
  1.9 1.10)

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Benchmark Suites

• SPEC (Standard Performance Evaluation
  Corporation)
• www.spec.org
• Benchmark types
• Desktop benchmarks
• Server benchmarks
• Embedded benchmarks

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Desktop Benchmarks

• SPEC Benchmarks
• SPEC CPU2000 (SPEC95, SPEC92, SPEC89) (Fig. 1.12)
• Graphic benchmarks
• SPECviewperf
• SPECapc
• Windows OS benchmarks (Fig. 1.11)
• Business Winstone
• CC Winstone
• Winbench

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Server Benchmarks

• SPEC
• File server benchmarks SPECSFS
• Measuring NFS performance
• Web server benchmarks SPECWeb
• Simulate multiple clients requesting both static
  and dynamic pages.
• TPC (Transaction-Processing Council)
• TPC-A, TPC-C, TPC-H, TPC-R, TPC-W
• Simulate a business-oriented transactions
  (queries)
• www.tpc.org

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Embedded Benchmarks

• EDN Embedded Microprocessor Benchmark Consortium
  (EEMBC) (Fig. 1.13)
• Automotive/industrial
• Consumer
• Networking
• Office automation
• Telecommunications

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Reporting Performance Results

• Guiding Principle
• The performance measurements should be
  reproducibility.
• Needs to tell
• Hardware configurations
• Software used
• Is source code modification for benchmarks
  allowed?

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Comparing Performance

• Computer A Computer B Computer C
• P1 (secs) 1 10 20
• P2 (secs) 1000 100 20
• Total time 1001 110 40
• Total execution time A consistent summary
  measure
• Another metrics
• Average execution time (arithmetic mean)
• Harmonic mean
• Weighted execution time
• Geometric mean

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Quantitative Principles of Computer Design

• Make the common case fast A fundamental law,
  called Amdahls Law, can be used to quantify this
  principle.
• Amdahls Law
• the performance improvement to be gained from
  using some faster mode of execution is limited by
  the fraction of the time the faster mode can be
  used.
• Amdahls Law defines speedup as
• Example on pages 41 and 42

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CPU Performance Equation

• Dependency
• Clock cycle time - Hardware technology and
  organization
• CPI - Organization and instruction set
  architecture
• Instruction count - Instruction set architecture
  and compiler
• Sometimes
• and overall
• Example on page 44.

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Measuring the Components of CPU Performance

• Clock cycle time Timing simulator or timing
  verifiers
• IC(instruction count)
• Direct measurement from running the applications
  on hardware
• Instruction set simulator - slow but accurate
• Instrumentation code approach the binary program
  is modified by inserting some extra code into
  every basic block. Fast but need instruction set
  translation if simulated machine differs from
  simulating machine.
• CPI very difficult to measure
• CPI Pipeline CPI Memory system CPI
• Basic block
• Labelxxx Branch Branch
  Label xxx
• Branch Branch Label xxx
  Label xxx
• Use the CPU performance equations to compute
  performance

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Principle of Locality

• Application of Amdahls Law
• A program spends 90 of execution time in on 10
  of the code.
• Temporal locality Recently accessed items are
  likely to be accessed in the near future.
• Spatial locality Items whose addresses are near
  one another tend to be referenced close together
  in time.

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Put it All Together

• Performance and Price-Performance
• Desktop computers
• Server computers
• Embedded processors

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Price and Performance of Desktops (1)
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Price and Performance of Desktops (2)
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Price and Performance of Servers (1)
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Price and Performance of Servers (2)
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PricePerformance of Embedded Processors (1)
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PricePerformance of Embedded Processors (2)
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PricePerformance of Embedded Processors (3)