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aarrcchhiitteeccttuurree ((221111))
Topic
Shared Memory MIMD Architecture
SUBMITTED TO SUBMITTED BY
Miss Kamalpreet kaur NAME Avdhesh sharma
COURSE B.Tech (cse) 150
REGG. NO. 10802037
ROLL NO. A 24
SEC c1801

2. ACKNOWLEDGEMENT
History of all great works into witness that no great work was ever done
without either active or passive support of a person ‘surrounding and
one’s close quarters. thus is it not hard to conclude how active
assistance from senior could positively impact the execution of a project
.I am highly thankful to our learned faculty Miss Kamalpreet Kaur for his
active guidance throughout the completion of project .
Last but not least, I would also want to extend my
appreciation to those who could not be mentioned here but have well
played their role to inspire me behind the certain.
AVDHESH SHARMA
Contents

3. 1>>Introduction to MIMD Architectures
2>>MIMD Architecture’s Goal
3>>Routing
4>>The types of deterministic routing
5>>Shared memory :bus based
6>>Shared Memory: Extended
7>>Shared Memory: Hierarchical
8>>Distributed Memory: Introduction
9>>Hypercube Interconnection Network
10>>Mesh Interconnection Network
11>> Bibliography
Introduction to MIMD Architectures

4. MIMD Architecture
Processor
A
Processor
B
Processor
C
Data Input
stream A
Data Input
stream B
Data Input
stream C
Unlike SISD, MISD, MIMD computer works asynchronously.
Shared memory (tightly coupled) MIMD
Distributed memory (loosely coupled) MIMD
Data Output
stream A
Data Output
stream B
Data Output
stream C
Instruction
Stream A
Instruction
Stream B
Instruction
Stream C
MIMD (Multiple Instruction stream, Multiple Data stream) computer system has a number of
independent processors operate upon separate data concurrently. Hence each processor has its
own program memory or has access to program memory. Similarly, each processor has its own
data memory or access to data memory. Clearly there needs to be a mechanism to load the
program and data memories and a mechanism for passing information between processors as
they work on some problem. MIMD has clearly emerges the architecture of choice for general-purpose
mutiprocessors. MIMD machines offer flexibility. With the correct hardware and
software support, MIMDs can function as single user machines focusing on high performance for
one application, as multiprogrammed machines running many tasks simultaneously, or as some
combination of these functions. There are two types of MIMD architectures: distributed memory
MIMD architecture, and shared memory MIMD architecture.

5. 1 MIMD Architecture’s Goal
Without accessibility to shared memory architectures, it is not possible to obtain memory access
of a remote block in a multicomputer. Rather than having a processor being allocated to different
process or having a processor continue with other computations (in other words stall),
Distributed MIMD architectures are used. Thus, the main point of this architectural design is to
develop a message passing parallel computer system organized such that the processor time
spent in communication within the network is reduced to a minimum.
II. Components of the MultiComputer and Their Tasks

6. Within a multicomputer, there are a large number of nodes and a communication network linking
these nodes together. Inside each node, there are three important elements that do have tasks
related to message passing :
a. Computation Processor and Private Memory
b. Communication Processor
This component is responsible for organizing communication among the multicomputer nodes,
"packetizing" a message as a chunk of memory in the on the giving end, and "depacketizing" the
same message for the receiving node.
c. Router, commonly referred to as switch units
The router’s main task is to transmit the message from one node to the next and assist the
communication processor in organizing the communication of the message in through the
network of nodes.
The development of each of the above three elements took place progressively, as hardware
became more and more complex and useful. First came the Generation I computers, in which
messages were passed through direct links between nodes, but there were not any communication
processors or routers. Then Generation II multicomputers came along with independent switch

7. units that were separate from the processor, and finally in the Generation III multicomputer, all
three components exist.
III. MultiComputer Classification Schemes
One method of classifying a multicomputer’s scheme of message transmission is its
interconnection network topology, which in plain English means how the nodes are
geometrically arranged as a network. There is great value in this information. The idea behind it
is related to the notion in computer science known as the Traveling Salesman problem, the
Shortest Path Algorithm from point A to point B(or in this case node A to node B) is directly
linked to the shape that the nodes generate when linked together. Interconnection network
topology has a great influence on message transmission.
Routing
Routing is the determination of a path, whether it is the shortest or the longest or somewhere in
between, from the source to the destination node. Two broad categories of routing exist---
deterministic and adaptive. In deterministic routing, the path is determined by the source and
destination nodes and in adaptive routing the intermediate nodes can "see" a blocked channel on
their way to their destination and can reroute to a new path. This works similar to the way people
normally alter their paths of traveling when hearing about the accident on I -495.
Deterministic routing has two more sub-categories that fall within it. One of them is named is
source routing, a method in which the source node determines the routing path to the destination.
The other method, distributed routing, considers all intermediate nodes and the source node in
determining the best path towards the destination, avoiding blocked channels.
THE TYPES OF DETERMINISTIC ROUTING
Source Routing Means----
Street Sign Routing
Street Sign routing requires that the message header carries the entire path information.

8. At each turn of the node, the path towards the destination has been predetermined. However each
message header also has the capability to choose a default direction in which case an
intermediate node’s channel is in use. It does this by comparing the node’s address to see if a
miss occurred.
Distributed Routing Schemes-----
Dimension Ordered Routing
Dimension ordered routing is best explained through a diagram provided in Figure 17.14 and is
a routing method in which a message moves along a "dimension" until it reaches the a certain
coordinate and moves through another dimension. This scheme only works if the source node
and destination node lie along different dimensions.
Table Lookup Routing
In this type of routing, a table is formulated so that any given node can go where to forward its
message. Of course, this style of routing eats away at a lot of hardware, but is good in software
usage. This is because a very huge lookup table will require a very big chip area.

9. Shared memory :bus based
MIMD machines with shared memory have processors which share a common, central memory.
In the simplest form, all processors are attached to a bus which connects them to memory. This
setup is called bus-based shared memory. Bus-based machines may have another bus that
enables them to communicate directly with one another. This additional bus is used for
synchronization among the processors. When using bus-based shared memory MIMD machines,
only a small number of processors can be supported. There is contention among the processors
for access to shared memory, so these machines are limited for this reason. These machines may
be incrementally expanded up to the point where there is too much contention on the bus.
Shared Memory: Extended
MIMD machines with extended shared memory attempt to avoid or reduce the contention among
processors for shared memory by subdividing the memory into a number of independent memory
units. These memory units are connected to the processsors by an interconnection network.

10. The memory units are treated as a unified central memory. One type of interconnection network
for this type of architecture is a crossbar switching network. In this scheme, N processors are
linked to M memory units which requires N times M switches. This is not an economically
feasible setup for connecting a large number of processors.
Shared Memory: Hierarchical
MIMD machines with hierarchical shared memory use a hierarchy of buses to give processors
access to each other's memory. Processors on different boards may communicate through
internodal buses. Buses support communication between boards. Wiuth this type of architecture,

11. the machine may support over a thousand processors.
Distributed Memory: Introduction
In distributed memory MIMD machines, each processor has its own individual memory location.
For data to be shared, it must be passed from one processor to another as a message. Since there
is no shared memory, contention is not as great a problem with these machines. It is not
economically feasible to connect a large number of processors directly to each other. A way to
avoid this multitude of direct connections is to connect each processor to just a few others. This
type of design can be inefficient because of the added time required to pass a message from one
processor to another along the message path. The amount of time required for processors to
perform simple message routing can be substantial. Systems were designed to reduce this time
loss and hypercube and mesh are among two of the popular interconnection schemes.
Hypercube Interconnection Network
In an MIMD distributed memory machine with a hypercube system interconnection network
containing four processors, a processor and a memeory module are placed at each vertex of a
square. The diameter of the system is the minimum number of steps it takes for one processor to
send a message to the processor that is the farthest away. So, for example, the diameter of a 2-
cube is 2. In a hypercube system with eight processors and each processor amd memory module

12. being placed in the vertex of a cube, the diameter is 3. In general, a system that contains 2^N
processors with each processor directly connected to N other processors, the diameter of the
system is N. One disadvantage of a hypercube system is that it must be configured in powers of
two, so a machine must be built that could potentially have many more processors than is really
needed for the application.
Mesh Interconnection Network
In an MIMD distributed memory machine with a mesh interconnection network, processors are
placed in a two-dimensional grid. Each processor is connected to its four immediate neighbors.
Wraparound connections may be provided at the edges of the mesh. One advantage of the mesh
interconnection network over the hypercube is that the mesh system need not be configured in
powers of two. A disadvantage is that the diameter of the mesh network is greater than the
hypercube for systems with more than four processors.
Bibliography with References:
This work presented here has been prepared and polished with the help of several
sources. I feel it my moral responsibility to express my sincere thanks to the
concentrators .I feel extremely obligated to the content creators of these resources
and truly appreciate their sprit.
http://carbon.cudenver.edu/~galaghba/mimd.html
http://www.answers.com/topic/mimd
http://www.springerlink.com/content/y0p232174k183t43/
http://www.cs.umd.edu/class/fall2001/cmsc411/projects/MIMD/mimd.html
http://www.ncl.cs.columbia.edu/publications/vv92.pdf

13. http://en.wikipedia.org/wiki/MIMD