1 types of processors

8/4/2019 1 Types of Processors

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Classification Based On Number

Of Processors

1. Single Processor Systems

2. Multiprocessor Systems3. Clustered Systems


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Single Processor Systems

One CPU present. Most commonly found, frommainframes to laptops.

special purpose processors may be present like:-

Math processor

Disk processor

Keyboard processor

Video processor

Audio processorI/O processor

Co-processor


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Multi Processor Systems

(Parallel or Tightly Coupled)

Have 2 or more General Purpose Processors in close

communication.

Normally the processors share the computer bus,

clock, memory and peripheral devices. Are of importance and are increasing in number.

Are much costlier but have 3 major advantages :-

1. Increased throughput2. Economy of scale

3. Increased reliability


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Increased throughput

Throughputis the amount of work that a

computer can do in a given time period.

Howeverspeed up ratio is not equal to N but a little

lesser, where N is the no. of processors (because the

bus, memory, peripheral devices are shared).


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Economy of scale

Works out cheaper or there is economy with scalingof processors.

Compare multipleSingle Processor System with a

singleMulti Processor System. Which costs lesser ?And Why?

1. They share power supplies

2. They share peripherals

3. They share mass storage4. If several programs ar operating on the same data

just one copy of the data is sufficient.


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Increased reliability

Failure of one processor need not halt the system. The

other processors can take up the work to completion.

Such systems are termed fault tolerantor systems

with graceful degradation


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Fault Tolerant

even if a processor or a component fails, the

operation of the system is not hindered.

faults are detected, diagonised and if possible

corrected too.Eg:- TheHP non-stop system or theHP tandem system

it uses both hardware and software duplication to

ensure continued operations. It has multiple pairs of CPUs which work in lock

step.


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Lock Step

A pair of processors will execute the same instructions

and will compare the results.

If there is a mismatch it means one CPU is corrupt.

Immediately both are halted. The executing process is carried out by another pair of

processors.

( is an expensive solution)


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Graceful Degradation

The ability to provide service proportional to the level

of surviving hardware is called graceful degradation.


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Types Of Multiprocessors

2 kinds namely symmetric and asymmetric

multiprocessors.


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Symmetric Multiprocessors

Are more common.

All CPUs are like peers.

If nprocessors present, nprocesses can getexecuted in true parallel way.

Eg:- Sun Solaris operating system.(it can beconfigured to employ dozens of processors all running

Solaris.)

What care has to be taken in SMS?


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Sophisticated I/O control is required to ensure that the

right data reaches the right processor.

Disparity among the processors to be minimised i.e.

one sitting idle and the other unduly gettingoverloaded.

Note:-All modern operating systems including

Windows, Windows XP, Mac OS X, and Linux

support SMP.


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Asymmetric Processors

Here each processor is assigned a distinct task.

A master processor controls all others.

The relationship amongst the processors is master-

slave.

The master processor schedules and allocates work to

the slaves.

Eg:- Sun OS (version 4) provided asymmetric

multiprocessing.


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Recent Trends in CPU design

Dual core processors and multicoreprocessors.

They are found in fast higher ended machines.

All the core cpus are kept in the same chip.

They look like n standard processors to the o.s.

Blade servers are a recent development. Their web

definition is here:-


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A blade server is essentially a housing for

a number of individual minimally-packaged

computer motherboard "blades", each

including one or more processors,memory, storage, and network

connections, but sharing the common

power supply and air-cooling resources ofthe chassis.


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Definition ofblade PC

A PC architecture that houses multiple PCmodules ("blades") in a single chassis.

It takes the machines off the users' desks and

houses them in rack mounted cabinets in thedatacenter similar to blade servers.

The user's keyboard, monitor and mouse pluginto a device at the desk that is wired via a

TCP/IP or direct connection to the assignedblade in the datacenter.


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Advantages Of Blade PCs

Having the physical PCs in the datacenterreduces noise andheatat users' desks.

the pcs are inherently secure in a locked room.

Data cannot be downloadedor uploaded because the USB

ports and hard disk drives are away from the desk.

Incase of user/employer relocation the actual machinerelocation is avoided.

If a PC fails, a spare blade may be available in each chassis for

hot swapping. Repairs are always performed in the same place, andtechnicians do not have to travel throughout the building.


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A Blade PC


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ClearCube Technologies was the first to make blade PCs,which were introduced in 2000.

This ClearCube cage contains eight fully functional PCs,each with its own storage (hard disk).

A one-foot rack can hold nearly 20 PCs. So there is goodspace management.

ClearCube management software backs up the data tospare network drives, periodically.

if a blade fails, the mgmt software is used, to switch theuser to a spare blade and restore the data.


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A Blade Server


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Blade servers such as this unit from HP

are widely used in datacenters to save

space and ease systems management.

Managed by HP's Insight Manager, this

unit has redundant power supplies .

The exposed blade (left) is a complete

server with hard disk.

----------------


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Clustered Systems

A computer clusteris a group of tightly coupledcomputers which work together closely, so thatin many respects they can be viewed as thoughthey are a single computer.

The components of a cluster are in most casesconnected to each other through fast LANs andthey also share storage.

Clusters are usually deployed to improve

performance and availability Also typically they are much more cost-effectivethan single computers of comparable speed.


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High Availability is possible by adding a layer ofredundancy.

Imagine a layer of cluster software which runs onthe nodes.

Each node is made to monitor 1 or 2 othernodes.

If by chance a monitored machine fails, themonitoring machine can take ownership and can

restart the application. (the users cannot really notice this. There will

be a small interruption of service, thats all.)


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Types Of Clustering

There are different kinds of clusters

namely namely:-

(i) Asymmetric

(ii) Symmetric

(iii) Parallel clusters

(iv) WAN clusters


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Assymetric Clustering

Means the machines are not alike in theirworking philosophy.

While one machine runs an application the

other is just a standby, also termed hotstandby.

The standby does nothing but monitors the

active server. And if the server fails the standby will take

over and will be the active server!


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Symmetric Clustering

Here, 2 or more hosts are running

applications and are monitoring one

another.

If one fails the other will take over.

This is more efficient because the

machines act alike and resources on both

machines get used fully.


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Parallel Clustering

Parallel clusters allow multiple hosts to

access the same data on the shared

storage. (cost effective & more reliable)

To provide multiple access simultaneously

the operating system too should provide

this facility and locking to ensure that no

conflicting operations occur.

This is termed distributed lock manager.


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However, since most operating systems

lack support forsimultaneous data

access by multiple hosts, special

versions of the software/applications arebeing used.

Eg:-Oracle parallel server is a version of

Oracles data base server designed to runon a parallel cluster.


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WAN Clusters

Custering over a wide area network

means the nodes are separated by high

distances. Eg:-a city area or so.


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SAN and clusters

Storage Area Networks allow many

systems to attach to a pool of storage.

If the applications and their data are

stored on the SAN, the cluster software

can assign the application to run on any

host.

If the host fails any other host can take

over.


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Grid computing

grid clusters are a technology closely related to clustercomputing.

The key differences (by definitions which distinguish thetwo at all) between grids and traditional clusters are that

grids connect collections of computers which do not fullytrust each other, or which are geographically dispersed.

Grids are thus more like a computing utility than like asingle computer.

In addition, grids typically support more heterogeneouscollections than are commonly supported in clusters.


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Grid computing is optimized for workloads which

consist of many independent jobs which do not

have to share data between the jobs during the

computation process. Grids serve to manage the allocation of jobs to

computers which will perform the work

independently of the rest of the grid cluster.

Resources such as storage may be shared by all

the nodes..


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An example of a very large cluster is thefolding@home project. It is analyzing data thatis used by researchers to find cures for diseasessuch as Alzheimer's and cancer.

Another large project is the seti@home project,which may be the largest distributed cluster inexistence. It uses approximately three millionhome computers all over the world to analyzedata from theArecibo Observatoryradiotelescope, searching for evidence ofextraterrestrial intelligence.
http://en.wikipedia.org/wiki/Arecibo_Observatoryhttp://en.wikipedia.org/wiki/Radiotelescopehttp://en.wikipedia.org/wiki/Radiotelescopehttp://en.wikipedia.org/wiki/Arecibo_Observatory


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Computing Environments

Traditional computing

Client-server computing

Peer to peer computing Web based computing

1 types of processors

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