Chapter 1
Computer Organization
Introduction
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Chapter 1
Why study this course?
“The computer lies at the heart of computing. Without it most of the computing disciplines today would be a branch of theoretical mathematics. To be a professional in any field of computing today, one should not regard the computer as just a black box that executes programs by magic. All students of computing should acquire some understanding and appreciation of a computer system’s functional components, their characteristics, their performance, and their interactions. There are practical implication as well. …” JTF01 cited in Stallings 2006, pp. 10
SSK3207 Chapter 1
SSK3207 Chapter 1
SSK3207
SSK3207
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Learning Outcomes
At the end of this chapter, student should be able to:
Describe main computer components
Describe functions of the components
Describe on how the components communicate with each other to perform a task
SSK3207 Chapter 1
SSK3207 Chapter 1
Topic
1.0 Introduction
1.1 Computer Main Components
1.2 Computer Functions
1.3 Interconnection Function
1.4 Bus Interconnection
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1.0 Introduction
Computer architecture – attributes that have a direct impact on the logical execution of a program.
Example architecture attributes :instruction set, the number of bit to represent various data types (e.g.., numbers, and characters), I/O mechanisms, and technique for addressing memory.
Computer organization refers to the operational units and their interconnection that realize the architecture specification.
Examples of organization attributes include those hardware details transparent to the programmer, such as control signals, interfaces between the computer and peripherals, and the memory technology used.
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1.0 Introduction (Cont..)
As an example, it is an architectural design issue whether a computer will have a multiply instruction.
It is an organizational issue whether that instruction will be implemented by a special multiply unit or by a mechanism that makes repeated use of the add unit of the system
The organization decision may be bases on the anticipated frequency of use of the multiply instruction, the relative speed of the two approaches, and the cost and physical size of a special multiply unit.
The distinction between architecture and organization has been an important one
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Many computer manufacturers offer a family of computer model, all with the same architecture but with differences in organization.
Consequently, the different models in the family have different price and performance characteristics.
Furthermore, an architecture may survive many years, but its organization changes with changing technology.
1.0 Introduction (Cont..)
1.1 Computer Main Components
Figure 1 is the simplest possible depiction of a computer. The computer is an entity that interacts in some fashion with its external environment.
In general, all of its linkages to the external environment can be classified as peripheral devices or communication lines. We will have something to say about both types of linkages.
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Figure 1: The computer: top-level structure
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1.2 Computer Function
The basic computer function is to execute programs, which includes:
Data Processing
Must be able to process data
The data may take a wide variety of forms and the range of processing requirements is broad
Data Storage
It is also essential that a computer store data at least temporarily store those pieces of data that are being worked on at any given moment.
Data Movement
Must be able to move data between itself and the outside world
Control
Control all the above three functions.
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1.2 Computer Function (Cont..)
There are 3 main computer components, i.e. CPU, MM and I/O unit that are interdependent when performing their respective tasks.
CPU will perform the processing tasks based on the instructions given by programs and control the operation of the computer.
The instructions are stored in MM and the CPU will fetch and execute them one at a time until all of them are completed.
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I/O Unit moves data between the computer and its external environment.
Generally, computers use Stored Program Concept to perform their tasks. This concept was introduced by John Von Newmann (1945)
Stored Program Concept – perform a variety of tasks in sequence or intermittently
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1.2 Computer Function (Cont..)
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Stored Program Concept
Data and instructions that will be executed are stored in a single read-write memory.
The contents of this memory are addressable by the location, without regard to the type of data contained there.
Instructions are executed sequentially based on their position in the memory (unless explicitly modified)
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1.2 Computer Function (Cont..)
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1.3 Interconnection Structure
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The components communicate with each other to perform a task.
The collection of paths connecting the various modules is called the System Interconnection Structure
The design of this structure will depend on the exchanges that must be made between modules
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1.3 Interconnection Structure (Cont..)
Types of transfer
Memory to CPU
CPU to memory
I/O to CPU
CPU to I/O
I/O to or from Memory (DMA)
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1.4 Bus Interconnection
A bus is a communication pathway connecting two or more device
A line or pathway that connects the 3 main computer components (Memory, CPU, I/O) is called System Bus.
A key characteristic of a bus is that is is a shared transmission medium
A bus consist of multiple pathway or lines
Each line is capable of transmitting signal representing binary digit ( 0 or 1)
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1.4 Bus Interconnection (Cont…)
For example, an 8-bit unit of data can be transmitted over 8 data bus lines.
The size or width of a bus is how many bits it carries in parallel. Common bus sizes are: 4 bits, 8 bits, 12 bits, 16 bits, 24 bits, 32 bits, 64 bits, 80 bits, 96 bits, and 128 bits.
The speed of a bus is how fast it moves data along the path. This is usually measured in MegaHertz (MHz) or millions of times a second.
The capacity of a bus is how much data it can carry in a second. In theory this is determined by multiplying the size of the bus by the speed of the bus, but in practice there are many factors that slow down a bus, including wait cycles (waiting for memory or another device to have information ready).
Generally, there are 4 ways to connect the 3 components with the I/O module acting as the control point :
(i) I/O to CPU (ii) I/O to MM (iii) I/O to Central Switch
(iv) I/O to Bus
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1.4 Bus Interconnection (Cont…)
A system bus consists of 50 – 100 lines
Each line assigned to a particular meaning or function
On any data bus, the lines can be classified into 3 groups
Data Lines
Address Lines
Control Lines
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1.4 Bus Interconnection (Cont..)
Bus Structure
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1.4 Bus Interconnection (Cont..)
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Data Bus: Used to transfer data/instructions from one component to another
Address Bus: Used to transfer the destination address of the data that is inside the Data Bus
Control Bus: Used to transfer signals that control data and address in Data Bus and Address Bus
Bus Structure
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1.4 Bus Interconnection (Cont..)
Traditional Bus Structure
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Multiple-Bus Hierarchies
Performance degrades if great number of devices are connected to the bus:
The more device attached, the greater the bus length
and greater propagation delay
The bus may become bottleneck – aggregate data
transfer demand capacity of the bus
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1.4 Bus Interconnection (Cont…)
Build to overcome the problem of high performance devices been introduced significantly, that request for faster response and greater speed.
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1.4 Bus Interconnection (Cont…)
High Performance architecture
Questions
SSK3207 Chapter 1
Named three(3) main components in computer architecture.
Give four (4) basic computer function is to execute programs
Give four (4) ways to connect the 3 (CPU, Memory, I/O) components with the I/O module acting as the control point
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