l31 multiprocessors

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  • 8/6/2019 L31 Multiprocessors



    Concept is used to improve performance and reliability


    Loosely Coupled Multiprocessing

    Functionally Specialized Processors

    Tightly Coupled Multiprocessing (multiprocessor)

    Parallel Processing

  • 8/6/2019 L31 Multiprocessors


    Characteristics of Multiprocessors

    Contains 2 or more similar general purpose processorsof comparable capability

    All processors share access to common memory.Some local or private memory may also be used

    All processors share access to I/O devices, eitherthrough same channels or through different channelsthat provide paths to the same devices

    System is controlled by an integrated OS. OS provides

    interaction b/w processors and their programs

  • 8/6/2019 L31 Multiprocessors


    Organization of Multiprocessor System

    1. Time-Shared or Common Bus

    2. Multiport Memory

    3. Central Control Unit

  • 8/6/2019 L31 Multiprocessors


    1. Time-Shared or Common Bus

    System bus is used for interconnection of all the

    components. The bus consists of data bus, controlbus, address bus

    It has provision for DMA transfers. To facilitate DMAtransfer Addressing, Arbitration and Time sharingfeatures are provided.


    Simplicity: Easy to design

    Flexibility: Easy to expand the system by

    attaching more CPUs to the bus

    Reliability: Failure of any attached device willnot cause failure of whole system

    Disadvantage: Speed of system limited by cycle time

  • 8/6/2019 L31 Multiprocessors


    2. Multiport Memory

    Allows direct, independent access to main memorymodules by each CPU and I/O module

    Logic is associated with memory to resolve conflicts The method used to resolve conflicts is to assign

    permanently priorities to each memory port

    This is more complex approach as compared to bus

    approach Performance is better as compared to bus approach

  • 8/6/2019 L31 Multiprocessors


    3. Central Control Unit

    Central control unit is responsible for transmittingdata streams back and forth between independentmodules

    The controller can buffer requests and performarbitration and timing functions

    Can also pass status and control information betweenCPUs

    Flexible & simple approach as a single control unitprovides interface to I/O, memory and CPUs

    Disadvantage: Control unit is quite complex

  • 8/6/2019 L31 Multiprocessors


    Multiprocessor Operating System

    In a tightly coupled multiprocessor system, OScontrols the operation of the system

    i.e. multiple jobs or processes may be active at a time,and OS schedules their execution and allocateresources

    7 common functions are identified for such OS:

    Resource Allocation and Management

    Table and Data Protection

    Prevention of System Deadlock

    Abnormal Termination

    I/O Load Balancing

    Processor Load Balancing


  • 8/6/2019 L31 Multiprocessors


    Types of Parallel Processors

    A parallel processor is a system in which multipleprocessors are interconnected and work collectively toexecute application program

    High-level parallelism e.g. system s/w andapplications

    Systems supporting Low-level parallelism areexcluded from this category

    E.g. of low level parallelism are:

    Instruction pipelining

    Multiple processor functional units

    Separate specialized processors

  • 8/6/2019 L31 Multiprocessors


    Types of Parallel Processors

    Parallel processors can be classified as (proposed byFlynn):

    Single instruction, single data (SISD) stream :Uniprocessors

    Single instruction, multiple data (SIMD) stream :Vector and array processors

    Multiple instruction, single data (MISD) stream :Not implemented commercially

    Multiple instruction, multiple data (MIMD) stream: Symmetric multiprocessor (SMP), NUMA, clusters

  • 8/6/2019 L31 Multiprocessors


  • 8/6/2019 L31 Multiprocessors


  • 8/6/2019 L31 Multiprocessors


  • 8/6/2019 L31 Multiprocessors


  • 8/6/2019 L31 Multiprocessors