pipeline and multiprocessor

1. Pipeline
 A pipeline is a set of data processing elements connected in
series,where the output of one elementis the input of the next
one.
 The elements of a pipeline are often executed in parallel or in time-
sliced fashion.
 In that case, some amount of bufferstorage is often inserted
between elements.
Computer-related pipelines include:
 Instruction pipelines
Such as the classic RISC pipeline, which are used in central
processing units (CPUs) to allow overlapping execution of multiple
instructions with the same circuitry.
 The circuitry is usually divided up into stages and each stage
processesone instruction at a time.
Examples ofstages are instruction decode,arithmetic/logic and
registerfetch.
 Graphicspipelines
Found in most graphics processing units (GPUs), which consistof
multiple arithmetic units, or complete CPUs.
That implementthe various stages of commonrendering operations:
perspective projection
Window clipping
Colour Light
Calculation
rendering, etc.

2.  Software pipelines: where commands can be written where the
output of one operation is automatically fed to the next, following
operation.
 The UNIX system call pipe is a classic example of this concept,
although other operating systems do support pipes as well.
 HTTP pipelining:where multiple requests are sent without waiting
for the result of the first request.
Concept and motivation
Pipelining is a natural conceptin everyday life
E.g. on an assemblyline.
Example:
 Considerthe assemblyof a car: assume that certain steps in the
assemblyline are to install the engine,installthe hood,and
install the wheels.
 A car on the assemblyline can have only one of the three steps
done at once.
 After the car has its engine installed, it moves on to having its hood
installed, leaving the engine installation facilities available for the
next car.
 The first car then moves on to wheel installation, the second car to
hood installation, and a third car begins to have its engine
installed.
 If engine installation takes 20 minutes, hood installation takes 5
minutes, and wheel installation takes 10 minutes, then finishing all
three cars
 When only one car can be assembled atonce would take 105
minutes. On the other hand, using the assemblyline,
 The total time to complete all three is 75 minutes.
 At this point, additional cars will come off the assemblyline at 20
minute increments.
Pipeline categories
 Linear pipelines
 Non-linear pipelines

3.  Linear pipelines
A linear pipeline processoris a series of processing stages and memory
access.
Non-linear pipelines
 A non-linear pipelining is also called dynamic pipeline.
 It can be configured to perform various functions at differenttimes.
 In a dynamic pipeline, there is also feed-forward or feed-back
connection.
 A non-linear pipeline also allows very long instruction words.
Design considerations
 One key aspectof pipeline design is balancing pipelinestages.
 Using the assemblyline example
 We could have greater time savings if both the engine and wheels
took only 15 minutes. Although the system latency would still be
35 minutes, we would be able to output a new car every 15
minutes.
 In other words, a pipelined process outputs finished items at a rate
determined by its slowest part.
 Another designconsiderationis the provisionof adequate
buffering betweenthe pipeline stages
 Especiallywhen the processing times are irregular, or when data
items may be created or destroyedalong the pipeline.
Graphical tools
To observe the scheduling of a pipeline (be it static or dynamic),
reservation tables are used.
Reservation table
 A reservation table for a linear or a static pipeline.
 It can be generated easily because data flow follows a linear
stream as static pipeline performsa specificoperation.
 In case of dynamic pipeline or non-linear pipeline a non-linear
pattern is followed so multiple reservation tables can be generated
for differentfunctions.

4.  The reservation table mainly displays the time space flow of data
through the pipeline for a function.
 Differentfunctions in a reservation table follow differentpaths.
 The number of columns in a reservation table specifies the
evaluation time of a given function.
Multiprocessing
 A multiprocessor systemis an interconnection of two or more CPUs with
memory and I/O equipment.
 IOPs aregenerally not included in the definitions of multiprocessor
systemunless they have computational facilities comparable to CPUs.
 Multiprocessor areMIMD system.
 Multicomputer systemincludes number of computers connected
together by means of communication lines.
Objective of multiprocessing
The key objective of using multiprocessing is the boostsystem executing
Speed executing speed and being fault tolerant and application
matching.
Examples
 A single central tower attach two computer system.
 Antenna attach two or moreLED’s
Explanation
 In multiprocessor all CPU’s may have equal functions or may be reserve
special functions.
 The multiprocessor is regarded as means to improve computing speed,
performance and cost effectiveness as wellas to provideenhance
availability and reliability