CAP_Chap_13

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Chapter - 13

Multiprocessor

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AMultiprocessor system is an interconnection of two or

more CPUs with memory and I/O equipments.

The processor means it may be either CPU or IOP.

Multiprocessors are classified as multiple instruction

stream, multiple data stream (MIMD) systems.

Multiprocessor system and multi-computer system support

concurrent operations.

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Difference between them is

Multi-computer system is a network of independent

computer.

Multiprocessor is controlled by one OS that provides

interaction between processors and all the components

of the system cooperate.

Mutiprocessing improving reliability of the system so that

a failure or error in one part has limited effect on the rest ofthe system.

If fault occurs in one processor, its task is assigned to

second processor.

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Benefit from multiprocessing in one of the two ways

Multiple jobs can be made to operate in parallel.

A single job can be partitioned into multiple parallel

tasks.

Multiprocessor with common shared memory is

classified as a shared memory or tightly coupled

multiprocessor.

In loosely-coupled system, each processor

element has its own private local memory.

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13.2 Interconnection Structures

The interconnection between components have different

physical configurations, depending on the number of

transfer paths in tightly coupled system or among the

processing elements in loosely coupled system.

1. Time- Shared common bus

2. Multiport memory

3. Crossbar switch

4. Multistage switching network

5. Hypercube system

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Time-shared common bus

ACommon Bus multiprocessor consists of a number ofprocessors connected through a common path to memory

unit.

Only one processor can communicate with memory at a

time.

Other processor wishing to transfer must first determine the

availability status of the bus, and only after the bus becomes

available can the processor address the destination unit to

initiate the transfer.

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Time shared common bus organization

Memory unit

CPU 1 CPU 2 CPU 3 IOP 1 IOP 2

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Multi-port Memory

AMultiport memory system employs separate buses

between each memory module and each CPU.

Each processor bus is connected to each memory module.

A processor bus consists of the address, data and control linesrequired to communicate with memory.

The memory module must have internal control logic to

determine which port will have access to memory at any

given time.

Fixed priority is assigned to each memory port.

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The advantage of the multi-port memory is the high

transfer rate because multiple paths between processors

and memory.

The disadvantage is that it requires expensive memory

control logic and large number of cables and connectors.

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Multiport memory organization

MM 1 MM 2 MM 3 MM 4

CPU 1

CPU 2

CPU 3

CPU 4