Upload
domainname9
View
234
Download
1
Embed Size (px)
Citation preview
8/6/2019 L31 Multiprocessors
1/14
Multiprocessing
Concept is used to improve performance and reliability
Classification
Loosely Coupled Multiprocessing
Functionally Specialized Processors
Tightly Coupled Multiprocessing (multiprocessor)
Parallel Processing
8/6/2019 L31 Multiprocessors
2/14
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
3/14
Organization of Multiprocessor System
1. Time-Shared or Common Bus
2. Multiport Memory
3. Central Control Unit
8/6/2019 L31 Multiprocessors
4/14
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.
Advantages:
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
5/14
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
6/14
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
7/14
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
Reconfiguration
8/6/2019 L31 Multiprocessors
8/14
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
9/14
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
10/14
8/6/2019 L31 Multiprocessors
11/14
8/6/2019 L31 Multiprocessors
12/14
8/6/2019 L31 Multiprocessors
13/14
8/6/2019 L31 Multiprocessors
14/14