Classifications of Computer Architecture
Summary
TLDRThis lecture delves into the classifications of computer architecture, focusing on two main models: Von Neumann and Harvard. Von Neumann architecture, also known as Princeton architecture, features a single path between the CPU and memory, leading to the Von Neumann bottleneck. In contrast, Harvard architecture separates instruction and data memory to overcome this limitation. The session also covers Flynn's taxonomy, categorizing architectures based on instruction and data streams, with SISD, SIMD, MISD, and MIMD types, providing a foundational understanding for modern processor design.
Takeaways
- 🏛️ Computer architecture is classified into two main categories: Von Neumann architecture and non-Von Neumann architecture.
- 🔍 Von Neumann machines have three basic hardware subsystems: CPU, main memory, and I/O system, and they operate as stored program computers with sequential instruction execution.
- 🔄 The Von Neumann bottleneck occurs when data and instructions share a single memory pathway, limiting simultaneous instruction and data processing.
- 🏫 The Harvard architecture, proposed by Harvard University, overcomes the Von Neumann bottleneck by using separate memory units for instructions and data, allowing parallel processing.
- 🛠️ Modified Harvard architecture combines elements of both Harvard and Von Neumann architectures, with a small, fast cache memory that can act as either depending on the access mode.
- 🤖 Flynn's taxonomy classifies computer architectures based on the number of instruction streams and data streams, such as SISD, SIMD, MISD, and MIMD.
- 🔢 SISD (Single Instruction Stream, Single Data Stream) is the category where Von Neumann architecture falls, with one CPU executing one instruction at a time.
- 🌟 SIMD (Single Instruction Stream, Multiple Data Stream) machines have multiple ALUs executing the same operation on different data sets in parallel, controlled by a single control unit.
- 🛑 MISD (Multiple Instruction Streams, Single Data Stream) is a theoretical category with no practical implementation, where different instructions operate on the same data item.
- 🔄 MIMD (Multiple Instruction Streams, Multiple Data Streams) refers to multiprocessors with independent processors, each executing different instructions on different data sets.
- 📚 Michael J. Flynn's classification system has been instrumental in the design and functionality of modern processors since its introduction in 1966.
Q & A
What are the two broad classifications of computer architecture discussed in the script?
-The two broad classifications of computer architecture discussed are Von Neumann architecture and non-Von Neumann architecture.
What are the three basic hardware subsystems of a Von Neumann machine?
-The three basic hardware subsystems of a Von Neumann machine are the CPU, the main memory, and the I/O system.
What is the main characteristic that defines a stored program computer?
-A stored program computer is defined by its ability to hold the program controlling the computer operation in the main memory, allowing the computer to manipulate its own program as well as any other data stored inside the memory.
What is the 'Von Neumann bottleneck' and why does it occur?
-The 'Von Neumann bottleneck' refers to the limitation where a processor cannot simultaneously read an instruction and operate on data because both instructions and data are fetched over the same path. This occurs in systems with pure Von Neumann architecture where instructions and data are stored in the same memory unit.
What is the Harvard architecture and how does it differ from the Von Neumann architecture?
-The Harvard architecture is a model that uses separate memory units for storing instructions and data items. This allows the processor to read an instruction and perform data memory access simultaneously, unlike the Von Neumann architecture where both operations share a single memory pathway.
What is the Modified Harvard architecture and how does it combine features of both Harvard and Von Neumann architectures?
-The Modified Harvard architecture is similar to the Harvard architecture but it relaxes the strict division of instruction memory and data memory. It includes a small, fast memory storage called caching. When the processor executes from the cache, it acts like a pure Harvard architecture, and when accessing from the backing memory, it acts like a pure Von Neumann machine.
What does SISD stand for in computer architecture and what are its characteristics?
-SISD stands for Single Instruction Stream, Single Data Stream. Computers in this category have one CPU that executes one instruction at a time and fetches and stores one item of data at a time.
What is SIMD and how does it differ from SISD?
-SIMD stands for Single Instruction Stream, Multiple Data Stream. Unlike SISD, SIMD machines have a control unit that operates like a Von Neumann machine executing a single instruction stream, but they have more than one ALU, allowing the execution of the same operation on different sets of data items in lock steps.
What is the difference between MISD and MIMD in Flynn's taxonomy?
-MISD stands for Multiple Instruction Streams, Single Data Stream, where theoretically different programs would execute on the same data items. MIMD stands for Multiple Instruction Streams, Multiple Data Streams, where each processor can execute a different set of instructions on its own set of data, making it suitable for parallel processing.
Who proposed the classification model used to categorize computer architectures by the number of processors, programs, and memory structures?
-The classification model was proposed by Michael J. Flynn in 1966, and it is commonly known as Flynn's taxonomy.
What is the significance of Flynn's taxonomy in the design of modern processors?
-Flynn's taxonomy is significant as it has been used as a tool in the design of modern processors and their functionalities, helping to understand and categorize different types of computer architectures based on their instruction and data handling capabilities.
Outlines
💾 Introduction to Computer Architecture Classifications
The video script begins with an introduction to the topic of computer architecture classifications. It explains that computer architecture can be broadly divided into two categories: Von Neumann and non-Von Neumann architectures. Von Neumann architecture, also known as Princeton architecture, is characterized by three basic hardware subsystems: the CPU, main memory, and I/O system. It is a stored-program computer where the program controlling the computer operation is stored in the main memory. This architecture is known for its sequential instruction execution and the single path between the main memory and the processor, which can lead to the Von Neumann bottleneck. The Harvard architecture, proposed by Harvard University, is a non-Von Neumann model that uses separate memory units for instructions and data, allowing for parallelism and overcoming the bottleneck issue. Modified Harvard architecture is also discussed, which combines elements of both Harvard and Princeton architectures, featuring a cache memory that can act as a pure Harvard architecture when executing from cache and as a Von Neumann machine when accessing from the backing memory. The script provides a detailed explanation of these classifications and their significance in modern processor design.
🔍 Flynn's Taxonomy of Computer Architectures
The second paragraph delves into the classification of computer architectures based on the number of instruction streams and data streams they handle. It introduces the concept of SISD (Single Instruction Stream, Single Data Stream), where computers like the Von Neumann architecture execute one instruction at a time and process one data item at a time. SIMD (Single Instruction Stream, Multiple Data Stream) is explained as architectures with a control unit that operates like a Von Neumann machine but with multiple ALUs executing the same operation on different data items in parallel. The paragraph also mentions MISD (Multiple Instruction Streams, Single Data Stream), which theoretically executes different programs on the same data but lacks practical implementation. Finally, MIMD (Multiple Instruction Streams, Multiple Data Streams), also known as multiprocessors, is described as architectures with more than one independent processor, each capable of executing different instructions on different data sets. This classification, proposed by Michael J. Flynn in 1966, is known as Flynn's taxonomy and has been instrumental in the design and functionality of modern processors.
Mindmap
Keywords
💡Computer Architecture
💡Von Neumann Architecture
💡Harvard Architecture
💡Von Neumann Bottleneck
💡Modified Harvard Architecture
💡SISC (Single Instruction Stream, Single Data Stream)
💡SIMD (Single Instruction Stream, Multiple Data Stream)
💡MISD (Multiple Instruction Streams, Single Data Stream)
💡MIMD (Multiple Instruction Streams, Multiple Data Streams)
💡Flynn's Taxonomy
Highlights
Introduction to the lecture on classifications of computer architecture.
Broad classification of computer architecture into Von Neumann and non-Von Neumann architectures.
Characteristics of Von Neumann machines including three basic hardware subsystems and stored program concept.
Sequential instruction execution in Von Neumann architecture leading to a single path debate.
The concept of Princeton architecture as an evolution of Von Neumann's model.
Harvard architecture's introduction of separate memory units for instructions and data to overcome Von Neumann bottleneck.
Understanding the need for Harvard architecture due to limitations in pure Von Neumann architecture.
Modified Harvard architecture combining features of both Harvard and Princeton models with caching.
Flynn's taxonomy as a classification model based on the number of instruction streams and data streams.
SISD (Single Instruction Stream, Single Data Stream) classification and its relation to Von Neumann architecture.
SIMD (Single Instruction Stream, Multiple Data Stream) classification and its application in processor arrays.
MISD (Multiple Instruction Streams, Single Data Stream) as a theoretical model with no practical implementation.
MIMD (Multiple Instruction Streams, Multiple Data Streams) as a category for multiprocessors with independent processors.
Practical applications of modified Harvard architecture in modern processors with caching mechanisms.
Flynn's taxonomy's impact on the design and functionality of modern processors since 1966.
Conclusion of the lecture with a summary of the two popular classifications of computer architecture.
Appreciation for the audience's attention and an invitation to the next lecture.
Transcripts
[Music]
well hello everyone welcome to the
session and as promised in this
particular lecture we are going to dive
right into various classifications of
computer architecture so without any
further ado let's get to learning now
coming to computer architecture's
classifications there are various models
among them we will be learning about two
most popular approaches so let's start
with the first one computer architecture
is broadly classified into specifically
two categories one newman architecture
and non-von neumann architecture now one
newman machines have the following
characteristics it has three basic
hardware subsystems the cpu the main
memory and the i o system
moreover it must be a stored program
computer that means the main memory
system holds the program which controls
the computer operation and the computer
can manipulate its own program more or
less also it can do the same to any
other data stored inside the memory
furthermore it carries out instructions
sequentially so the cpu appears to
execute one operation at a time well the
major debate has always been about
having a single path between the main
memory and the processor proposed by
this very architecture now already in
our previous discussion we came to know
about von neumann's professorship at
princeton university and that is the
reason why this architecture was also
referred to as princeton architecture
now people from harvard university
proposed another model which adopted
most of the features proposed in the
princeton architecture except for the
fact they used two different memory
units and thus pioneered parallelism
this is popularly known as harvard
architecture let's try to understand the
need of it first of all systems having
pure von neumann architecture stores the
instructions and the data in the same
memory unit thus both the data and the
instructions are phased over the same
path
this means the processor can't
simultaneously read an instruction and
operate on data this phenomenon is known
as von neumann bottleneck and was first
officially discussed by the great john
backers inventor of backus normal form
for context free languages during his
1977 acm turing hour lecture next there
is modified harvard architecture which
cannot completely be classified as von
neumann architecture as it doesn't
strictly follow the von neumann
principles but it is more of a
combination between both the harvard and
the princeton architecture now let's
study them in a bit details
now in harvard architecture we have
separate memory units
one is for strictly storing the
instructions and the other for the data
items
this way the processor can both read an
instruction and perform data memory
access at the same time therefore
computers belonging to this architecture
family are faster because instruction
fetches and data accesses are not
competing for the single memory pathway
anymore now coming to modified harvard
architecture it is very much like the
harvard architecture itself however it
relaxes the strict division of
instruction memory and data memory here
the processor is accompanied by a small
yet fast memory storage called caching
when the processor is executing from the
cachet it acts as a pure harvard
architecture and when it is accessing
from the backing memory it acts like a
pure von neumann machine this
modification it wide spread in modern
processors so this was the first
approach of classification of computer
architecture
let's move on to the next one in this
model computer architectures are
classified by a variety of
characteristics including the number of
processors the number of programs they
can execute and the memory structures
being used the first group is sisd that
is single instruction stream single data
stream the von neumann architecture
belongs to this specific category sisd
computers have one cpu that executes one
instructions at a time hence single
instruction stream and fetches and
stores one item of data at a time hence
single data stream the next group is
simd that is single instruction stream
multiple data stream
processor array falls into this category
simd machines have a control unit that
operates like a von neumann machine that
executes a single instructions stream
but they have more than one alus the
control unit generates the control
signals for all the alus which execute
the same operation on different set of
data items generally in lock steps hence
multiple data streams
the next group of computers are misd
multiple instruction streams single data
stream logically machine of this class
would execute various different programs
on the same data items this group
doesn't have any particular practical
implementation nonetheless some machines
belonging to the next category can be
used in this manner all right the next
and the final type is mimd multiple
instruction streams multiple data
streams machines these are also known as
multiprocessors
these are comprised of more than one
independent processors and each one of
them can execute a different set of
instructions hence multiple instruction
streams on its own set of data hence
multiple data streams now this
classification was proposed by michael j
flynn in 1966
since then it has been used as a tool in
design of modern processors and their
functionalities that is why it is also
known as flynn's taxonomy
alright folks that was the two most
popular classifications of computer
architecture hope you liked it and
learned something new i'll see you guys
in the next one thank you all for
watching
[Applause]
[Music]
you
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