ECE 456 Computer Architecture

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ECE 456 Computer Architecture

• Lecture 2 - Architecture Organization
• Instructor Dr. Honggang Wang

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Administrative Issues (9/18/13)

• Project team set-up due Wednesday, Sept. 25
• If you missed the first class, go to the course
  website for syllabus and 1st lecture.
• My office hours
• M./W. 11 am -12pm, Fri. 1200 -200 pm

www.faculty.umassd.edu/honggang.wang/teaching.html
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Agenda

• Review Lecture 1
• Lecture 2

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Review of Lecture 1

• In the first lecture, we covered the
• Course syllabus operational details
• Introduction to computer systems
• History of computers (a number of Firsts...)
• Evolution of Intel family
• The evolution of computers has been characterized
  by increasing processor speed/memory capacity/I/O
  capacity speed and decreasing component size
• Performance balancing is a critical issue in
  computer system design

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The First

• The first general-purpose electronic digital
  computer
• The first computer to use the Stored Program
  concept
• The first computer bug
• The first transistor
• The first chip (integrated circuit)
• The first minicomputer
• The first microprocessor

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The first general-purpose electronic digital
computer

• ENIAC (Electronic Numerical Integrator And
  Computer)
• designed by Mauchly Eckert at the U.
  Pennsylvania
• started 1943, finished 1946
• disassembled 1955
• 18,000 vacuum tubes
• 30 tons
• 30 feet 50 feet
• 140 kw power consumption

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The first computer to use the Stored Program
concept

• IAS computer named for the Institute for
  Advanced Study at Princeton University
• Began 1946, completed 1952
• The prototype of all subsequent
• general-purpose computers
• Structure
• Von Neumann machines

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The first computer bug

• Grace Hopper found a moth stuck in a relay
  responsible for a malfunction
• An error in a computer program that prevents it
  from working correctly or produces an incorrect
  result

http//www.jamesshuggins.com/h/tek1/first_computer
_bug.htm
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The first transistor

• Invented at Bell labs in 1947
• Won a Nobel prize
• Uses Silicon
• Advantages

http//www.cedmagic.com/history/transistor-1947.ht
ml William Shockley (seated at Brattain's
laboratory bench), John Bardeen (left) and Walter
Brattain (right)
http//en.wikipedia.org/wiki/Transistor
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The first chip

• Invented by Jack Kilby at Texas Instruments in
  1958
• Integrated Circuits are transistors, resistors,
  and capacitors integrated together into a single
  chip
• Won a Nobel prize

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The first minicomputer - 1964

• DEC PDP-8
• Small enough to sit on a lab bench
• Embedded applications
• Flexible bus structure

...
Console controller
CPU
Main memory
I/O module
I/O module
Omnibus
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The first microprocessor 1971

• The Intel 4004 had 2,250 transistors
• four-bit
• 108Khz
• Called Microchip

The Pioneer 10 spacecraft used the 4004
microprocessor. It was launched on March 2, 1972
and was the first spacecraft and microprocessor
to enter the Asteroid Belt.
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Lecture 2 Topics

• Concept of computer architecture computer
  organization
• Contemporary computer architecture is
• von Neumann architecture, plus
• Interrupts

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What is Computer Architecture?

• Term coined by IBM System/360 group in 1964
• The structure of a computer that a machine
  language programmer must understand to write a
  correct program for a machine
• cited from Advanced Computer Architecture A
  Design Space Approach, by D. Sima et al,
  Addison-Wesley 1997
• attributes visible to a programmer registers,
  instruction set, instruction formats, addressing
  modes, etc
• example Is there a multiply instruction?

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What is Computer Organization?

• The operational units and their
  interconnections that realize the architectural
  specifications
• about how features are implemented
• hardware details transparent to programmers
  control signals, interfaces, memory technology
• example Will the multiply instruction be
  implemented by a hardware multiply unit or
  repeated addition?

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Architecture Organization

• A particular architecture can span many years and
  encompass a number of different computer models
  (organizations)
• all Intel x86 family share the same basic
  architecture
• IBM System/370 family share the same basic
  architecture
• organization, thus price and performance differ
  between different models
• this gives code compatibility

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Agenda

• Concept of computer architecture computer
  organization
• Contemporary computer architecture is
• von Neumann architecture, plus
• Interrupts

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Von Neumann Architecture

• General structure of von Neumann machines (the
  IAS computer)

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The IAS Computer(prototype of modern computers)
Chapter 2.1
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Memory of IAS

• Memory 1000 words /storage locations
• 40 binary bits per word
• both data and instructions can be stored
• memory format for a number
• memory format for instructions
  

0
1
39
Sign bit
0
39
8
20
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Opcode Address
Opcode Address
Right instruction
Left instruction
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Instruction Set of IAS

• 21 instructions
• data transfer between memory and registers or
  between two registers
• unconditional branch
• conditional branch
• arithmetic
• address modify

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Table 2.1The IAS Instruction Set
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IAS Registers

• Memory Buffer Register (MBR) contains a word to
  be stored in memory or sent to I/O, or is used to
  receive a word from memory or I/O
• Accumulator (AC) Multiplier Quotient (MQ)
  employed to hold temporarily operands and results
  of ALU operations.
• Memory Address Register (MAR) specifies the
  memory address for the word to be written from or
  read into MBR.
• Instruction Register (IR) contains the 8-bit
  opcode of the instruction being executed
• Instruction Buffer Register (IBR) employed to
  hold temporarily the right-hand instruction from
  a word in memory
• Program Counter (PC) contains the address of the
  next instruction-pair to be fetched from memory

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Operation of IAS

• Instruction cycle
• Fetch
• Opcode ? IR
• Address ? MAR
• Execute

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Von Neumann Architecture Key Characteristics

• Memory with addressable locations
• Data and instructions are stored in a single
  read-write memory
• Basic sequential execution (unless explicitly
  modified)

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Administrative Issues (9/23/13, Monday.)

• Project Team
• due Wednesday, Sep 25
• Homework 1
• Assigned today, please go to the course website
  to download problems
• Todays topic
• Finish Lecture 2 (Interrupt)

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Agenda

• Concept of computer architecture computer
  organization
• Contemporary computer architecture is
• von Neumann architecture, plus
• interrupts

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Interrupts

• All contemporary computers provide a mechanism by
  which other modules may interrupt the normal
  processing of the processor
• Contemporary computer architecture
• von Neumann architecture interrupts

Chapter 3.2
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Common Classes of Interrupts

• Program interrupt
• division by zero, using undefined instructions,
  memory protection violations, arithmetic overflow
• Timer interrupt
• generated by an internal processor timer
• I/O interrupt
• Programmer-requested interrupt
• Hardware failure
• power failure, hardware malfunctions

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Why Interrupts? (1)

• Program flow of control without
• interrupts
• Code segments
• 1,2,3 do not involve I/O
• 4 prepare for actual I/O operation
• Actual I/O command
• 5 complete I/O operation

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Why Interrupts? (2)
Why Interrupts? (2) -- Program Control flow
Timing No Interrupts

• I/O devices are much slower than processor -- a
  very wasteful use of processor
• At the point of each WRITE call, processor must
  pause and remain idle

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Why Interrupts? (3)

• With interrupts, the processor can be engaged in
  executing other instructions while an I/O
  operation is in progress
• improved processing efficiency
• concurrency

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Illustration Short I/O Wait

• Time required for the I/O operation is less than
  the time to complete the execution of
  instructions between write calls in the user
  program.

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Why Interrupts? (4)
Why Interrupts? (4) -- Program Control Flow
Timing with Interrupts Short I/O Wait
concurrency
gain in efficiency
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Illustration Long I/O Wait

• Time required for the I/O operation is more than
  the time to complete the execution of
  instructions between write calls in the user
  program.

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Why Interrupts? (5) -- Program Control Flow
Timing with Interrupts Long I/O Wait
concurrency
gain in efficiency
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Summary

• With the use of interrupts, concurrent execution
  of user program and I/O operation is made
  possible!
• Improved CPU processing efficiency!

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Transfer of Control via Interrupts
Execution suspended with context saving
Execution resumed with context recovery
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Multiple Interrupts

• Various interrupt sources multiple
  interrupts
• How to deal with multiple interrupts?

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How to deal with multiple interrupts?

• Can an interrupt be interrupted while it is being
  processed?
• NO sequential interrupt processing
• YES which interrupt should the CPU service?
  
• priorities and nested interrupt
  processing

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Sequential Interrupt Processing (1)

• Disable interrupt (DI) while processing an
  interrupt, enable interrupt (EI) before resuming
  the use program

DI
EI
EI
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Sequential Interrupt Processing (2)

• Advantages
• simple all interrupts are handled in strict
  sequential order
• Disadvantages
• without considering relative priority or
  time-critical needs

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Nested Interrupt Processing (1)
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Nested Interrupt Processing (2) Example

• A system has three I/O devices
• a printer with priority 2
• a disk with priority 4
• a communication line with priority 5
• Multiple interrupts (each takes 10 time units)

Increasing priority
time
0
25
15
10
20
communication line interrupt
printer interrupt
disk interrupt
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Time Sequence of Example Multiple Interrupts
time
0
25
15
10
20
disk Interrupt (4)
printer Interrupt (2)
comm. line Interrupt (5)
2
1
3
4
6
5
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Nested Interrupt Processing (4)

• Advantages
• taking into account relative priority or
  time-critical needs
• Disadvantages
• complex defining priorities, saving information

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Summary of Lecture 2

• Basic concept of computer architecture and
  organization
• Von Neumann architecture (3 key concepts)
• Interrupts and multiple interrupts
• Contemporary computer architecture is von Neumann
  architecture, plus interrupts

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Things To Do
Next Topics

• Computer function structure

• Find your partners for the class project
• email me the team information
• Check out the class website about
• lecture notes
• reading assignments
• the project