Flynn's Classification

1. COMPUTER ORGANIZATION AND
ARCHITECTURE
PRESENTED BY:
NAYAN GUPTA
TOPIC :- FLYNN’S CLASSIFICATION

2. Introduction to
Flynn's Classification

3. • Flynn's Classificaton is the most popular
taxonomy of computer architecture,
proposed by Michael J.Flynn in 1966 based
on number of instruction and data.
• It is based on the notion of a stream of
information .

4. There are two types of
Instructions
flow into a processor
Data Stream
It is defined as the sequence of
data including inputs,partial,or
temporary results,called by
instruction stream.
Instruction Stream
It is defined as the sequence of
instruction executed by the
processing unit

5. Flynn's
Classification
Single Multiple
SIMD MISD MIMD
SISD

6. CLASSIFICATION
• SISD (Single Instruction Single
Data)
• SIMD (Single Instruction
Multiple Data)
• MISD (Multiple Instruction
Single Data)
• MIMD (Multiple Instruction
Multiple Data)

7. • An SISD computing is a Uni-processor
machine which is capable of executing
a single instruction, operating on a
single data stream.
• Single instruction: only one
instruction stream is being acted on by,
the CPU during any clock cycle.
• Single data: only one data stream is
being used as input during any one
clock cycle.
SISD (Single Instruction Single
Data)

8. • Conventional single processor Von-Neumann
computer are classified as SISD system.
• Instruction are executed sequentially but may be
overlapped in their execution stages (Pipelining).
Most SISD Uni-processor system are pipelined.
• SISD computers may have more than functional
units, all under the supervision of control unit.

9. • It's a serial(non-parallel) computer.
• Instruction are executed
sequentially but may be overlapped
in their execution stages
(Pipelining). Most SISD Uni-
processor system are pipelined.
• Examples-single CPU workstation,
Minicomputers, Mainframes, CDC-
6600

10. CU MM
PU

11. load A
C = A + B
store C
A = B * 2
store A
load B
TIME
Single
Instruction
Single Data

12. Advantages
• It requires less power.
• Simplicity
• It is relatively easy to design
and implement .
Disadvantages
• This architecture cant take
advantage of parallelism to
speed up computation.
• They struggle to handle
multiple task simultaneously

13. SIMD (Single Instruction
Multiple Data)
SIMD represents single-instruction multiple-data streams. The SIMD model of parallel
computing includes two parts such as a front-end computer of the usual Von-
Neumann style.
1.The processor array is a collection of identical synchronized processing elements adequate for
simultaneously implementing the same operation on various data.
2. Each processor in the array has a small amount of local memory where the distributed data
resides while it is being processed in parallel.
3.The processor array is linked to the memory bus of the front end so that the front end can
randomly create the local processor memories as if it were another memory.

14. A single instruction is executed on multiple
different data streams. These instructions
can be performed sequentially, taking
advantage of pipelining, or in parallel using
multiple processors. Modern GPUs,
containing Vector processors and array
processors, are commonly SIMD systems.
Common usage:
• Graphics Processing Units when
performing vector and array
operations.
• Scientific processing

15. SIMD Architecture Diagram
Instruction Pool
Data
Pool
PU
PU
PU
PU

16. Advantages Disadvantages
• Same operation on
multiple elements can
be performed using one
instruction only.
• Processing speed is
higher than SISD
architecture.
• It requires large register
which results in large
area and large power.
• The cost is higher than
SISD architecture.

17. • An MISD computing system is capable
of execution different instruction on
different PUs but all of them operating
on the same dataset.
• Multiple instruction: Each processing
unit may have different instruction
stream.
• Single data: Every processing unit can
operate on a same element.
MISD (Multiple
Instruction Single Data)

18. • Machines built using the MISD
model are practically not useful is
most of the applicaton, a few
machine are built, but none of
them are available commercially
because they are highly
specialized.
• Example: Systolic Arrays,
Space Shuttle flight control
system

19. Instructionl
PU
PU
PU
PU
Data
MISD Architecture Diagram

20. prev instruction
load A(1)
C(1) = A(1) * 1
Store C(1)
next instruction
prev instruction
C(n) = A(1) / n
load A(1)
C(2) = A(1) + 2
Store C(2)
next instruction
prev instruction
load A(1)
Store C(n)
next instruction
P1 P3
P2

21. Advantages Disadvantages
• There is complex
communication between
number of cores of
processor.
• The cost is higher than
SISD architecture.
• Excellent for situation
where fault tolerance is
critical.

22. MIMD (Multiple Instruction
Multiple Data)
• An MIMD system is a Multiprocessor machine which
is capable of executing multiple instructions on
multiple data sets.
• Each process in the MIMD model has separate
instruction and data streams.
• Machines built using this model are capable to any
kind of application.
• MIMD machines doesn’t rely on other processes.

23. Types of MIMD System
Shared-Memory
MIMD
Distributed-Memory
MIMD

24. Shared-Memory MIMD
• Tightly coupled Multiprocessor Systems.
• All the processes are connected to a single global
memory, and they all have access to it.
• The communication between processes in this model
takes place through the shared memory.
• Data stored in the global memory by one process is
visible to all other processes.

25. Shared-Memory MIMD
Shared
Memory
PE2
PE1
PEn
CU1
CU2
CUn
IS
IS
IS
DS
DS
DS

26. Distributed-Memory MIMD
• Loosely coupled Multiprocessor Systems
• All processes have a local memory.
• The communication between processes is done
through an interconnection network.
• The network connecting processes can be configured
in accordance with the requirement.

27. Distributed-Memory MIMD
Interconnection
Network
PE
CU
M
PE
CU
M
PE
CU
M

28. Shared-Memory Distributed-Memory
Easier to program. Complex to program.
Harder to extend. Easier to extend.
Less tolerant to failures. More tolerant to failures.
Failures affect the entire system.
Failures only affect a single process and
its memory and can be easily isolated.
Processes can lead to memory
contention.
No memory contention.