Computer Architecture Lecture Notes Spring 2005 Dr. Michael P. Frank

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Computer Architecture Lecture Notes Spring
2005Dr. Michael P. Frank

• Competency Area 1
• Computer System Components

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Why Study Computer Architecture?

• According to William Stallings text, the IEEE/ACM
  Computer Curricula 2001 Joint Task Force reported
  the following
• The computer lies at the heart of computing.
  Without it most of the computing disciplines
  today would be a branch of theoretical
  mathematics. To be a professional in any field
  of computing today, one should not regard the
  computer as a just a black box that executes
  programs by magic. All students of computing
  should acquire some understanding and
  appreciation of a computer systems functional
  components, their characteristics, their
  performance, and their interactions. Students
  need to understand computer architecture in order
  to structure a program so that it runs more
  efficiently on a real machine. In selecting a
  system to use, they should be able to understand
  the tradeoffs among various components, such as
  CPU clock speed versus memory size.

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Computer System Components

• In most generalizations of computers, there are
  essentially five classic components that are
  designed
• Input Systems (e.g. keyboard, mouse)
• Output Systems (e.g. Monitor display, printer)
• Memory (contains stored programs and memory)
• Control (component that controls memory, I/O,
  datapath)
• Datapath (component that performs arithmetic
  operations)

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Computer System Components

• Some Terminology General Definitions
• Because of the binary nature of computers, we
  typically use powers of 2 to represent large and
  small numbers. However, normal usage requires
  powers of 10 expressions. For example, we often
  use powers of 2 for describing memory capacities
  and powers of 10 for clock frequencies.

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Computer System Components

• A byte refers to 8 bits. A nibble is half a byte
  or 4 bits.
• A word is a group of bits that is processed
  simultaneously. Typical words sizes are 8, 16,
  and 32.
• Bits in a word can be numbered from left to right
  (little endian) or from right to left (big
  endian).
• The leftmost bit is called the Most Significant
  Bit (MSB).
• The rightmost bit is called the Least Significant
  Bit (LSB).
• Other terms UNITS seconds (s), bits (b), bytes
  (B), words (w). For example, Gb/s ns MB Mb
• Reciprocal seconds are called Hertz (Hz), so a
  clock period of 100ns corresponds to a clock rate
  of 10 MHz.

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Computer System Components

• Bits are used to represent both instructions and
  data.
• Initially only binary numbers are used to design
  and program computers, however this became
  tedious. Hence, the development of assembly
  language and high-level programming languages.
• The notion of low-level and high-level
  programming is a common approach to hardware and
  software system design.
• A system that consists of hierarchical layers
  with each lower layer hiding the details from the
  layer above it is known as abstraction.

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Computer System Components

• Levels or layers of Abstraction can be though of
  as the highest user level to the lowest level
  (transistor level).
• Separability is the key to effective computer
  abstraction. For example, if you run Microsoft
  Word or some other word processing program, you
  dont need to know anything about the
  inner-workings of its programming.
• Exploiting separability supports the development
  of upwardly-compatible machines (allows a user to
  upgrade to a faster, more capable machine without
  rewriting the software the runs on the less
  capable machine)

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Computer System Components
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Computer System Components

• To understand and appreciate computer systems, we
  must study the computer from several different
  aspects
• USER Perspective
• User Level and Applications High-level Languages
• Machine Language Programmers Perspective
• Assembly Language/Machine Coding
• Computer Architects Perspective
• Hardwired Control and Functional Units
  Performance
• Computer Logic Designers Perspective
• Logic Gates, Transistors and Wires

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Computer System Components

• Lets continue our discussion of the computer
  from a USERS PERSEPECTIVE
• The user is the person who is using the
  computer to perform useful work.
• The user is not concerned about the internal
  structure of the machine. Only that it is capable
  of performing applications such word processing,
  spreadsheets, programming, etc.
• The user is interested in the operating system
  and the application software.
• This perspective is only aware of
• Computer Speed (how fast will the computer run my
  programs)
• Storage Capacity (how much data can I store in
  computer)
• Behavior of peripheral devices (can I send data
  to a printer, etc.)

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Computer System Components

• Consider the MACHINE LANGUAGE PROGRAMMERS
  PERSEPECTIVE
• The machine language programmer is concerned
  with the behavior and performance of the
  computer system when it is programmed at the
  lowest level (machine language).
• To fully understand this perspective, we must
  define some terms
• Machine Language The collection of all the
  fundamental instructions that the machine can
  execute, expressed as a pattern of 1s and 0s.
• Assembly Language The alphanumeric equivalent of
  the machine language. Alphanumeric mnemonics are
  used as an aid to the programmer, instead of 1s
  and 0s.
• Assembler A computer program that converts
  assembly language to machine language.

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Computer System Components

• Lets examine some assembly language
  instructions
• The first instruction adds the contents of 32-bit
  register s2 to the contents of register s3 and
  places the sum in register t0. A register is a
  storage unit capable of holding a collection of
  bits. Registers s2, s3, and t0 are known as
  operands.
• The corresponding machine language is shown. The
  first field is known as the operational code
  (a.k.a opcode). The opcode specifies the
  particular operation to be performed.
• We will learn more about assembly language
  programming and coding later when we discuss
  instruction set architectures.
• Assembly languages and machine codes are specific
  to the architecture that is being used.

MIPS Assembly Language Machine Language
ADD t0, s2, s3 000000 10010 10011 01000 00000 100000
LW s1, 100(s2) 100011 10010 10001 00000 00001 100100
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Computer System Components

• The collection of all the operations in a
  machines language is its instruction set.
• A programmer is concerned with the machine and
  assembly language instruction set, as well as the
  machine resources that can be managed with those
  instructions.
• The collection of instructions and resources is
  known as the Instruction Set Architecture (ISA)
  of a computer, which includes
• Instruction Set
• Machines memory
• All programmer-accessible registers in the CPU

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Computer System Components

• The tools of the trade for the machine language
  programmers perspective are the following
• ASSEMBLER translates assembly language
  statements to their binary equivalent.
• LINKER links separately assembled modules into
  a single module suitable for loading and
  execution. Essentially, translating high-level
  languages (e.g. C, FORTRAN) into programs
  capable of execution.
• DEBUGGER Low-level programs that perform
  error-checking of assembly language programs
  allowing programmer to perform step-by-step
  troubleshooting techniques.
• DEVELOPMENT SYSTEMS collection of hardware and
  software tools that is used to support system
  development.

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Computer System Components

• Consider the COMPUTER ARCHITECTS PERSEPECTIVE
• The computer architect is concerned with the
  design and performance of the computer system as
  a whole.
• The architects job is to design a system that
  will provide optimum performance in the context
  of its users. This is essentially known as the
  constrained optimization problem.
• The constraints may include
• Cost
• System Size
• Memory Capacity
• Thermal or mechanical durability
• Availability of components
• Immunity static charge
• Time to completion

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Computer System Components

• From given constraints, performance
  specifications are defined such as processing
  speed, memory size, networkability, graphics
  resolution, etc.
• Architects use performance measurement tools to
  determine whether systems meet to specs
  identified. Usually these include benchmarks,
  simulations, etc. These are the tools of the
  trade for architects.
• Key Concepts
• The architect is responsible for the overall
  system design and performance.
• Performance must be measured against quantifiable
  specifications.
• The architect is likely to become involved in
  low-level details of of the computer design.
• The architect often uses formal description
  languages (e.g. RTL) to convey details of the
  design to other parts of the design team.
• The architect strives for harmony and balance in
  system design.

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Computer System Components

• Consider the COMPUTER LOGIC DESIGNERS
  PERSEPECTIVE
• The computer logic designer is concerned about
  the machine at the logic gate level. Usually
  the computer architect takes the role of the
  logic designer because their functions overlap.
• The logic designer deals with the implementation
  domain, which is a collection of hardware devices
  that make up a machine.
• The logic gate implementation domain may be
• VLSI on silicon
• Transistor-transistor logic (TTL) chips
• Emitter-coupled logic (ECL)
• Programmable logic arrays (PLAs)
• Optical switches, etc.

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Computer System Components

• The implementation domain is important because of
  the translation of the abstract level of logic
  gates to the concrete or practical domain.
• How can we most efficiently implement the logic
  gate design needed for the system using the
  hardware available?
• For example, if a designer is implementing a
  system using VLSI on silicon, the number and size
  of the processors registers may be affected by
  the amount of silicon is available on the chip.
• Tools of the trade for the designer include CAD
  tools and IC design tools.

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Computer System Components

• Our primary concern in this class includes
• Assembly language programming
• System design and performance
• Well discuss some aspects of the logic
  designers perspective such as gatelevel
  implementation of arithmetic operations.
• Other aspects of logic designers view is covered
  in courses like FPLDs, IC Design (Mixed and
  Digital), DSP for FPGAs, etc.
• The users perspective is covered in courses like
  C programming and MATLAB design.
• Next time well look different computer
  architectures from an historical perspective

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Class Exercise

• Answer the following questions based on the
  information presented in todays lecture
• How many bytes are contained in a 32-bit word?
• The Tolstoy novel War and Peace has 696 pages. A
  CD-ROM can store approximately 600 MB of
  information. One character can be stored in one
  byte. Can the contents of the book be stored on
  a single CD-ROM? Show your calculations.
  (Assume each page contains 50 lines and there are
  approximately 100 characters per line.)