Computer Architecture: Components & Organization

Introduction to Computer Architecture and Organization

• This is Chapter 1, by Kassahun T.

Basic Computer Organization

• Computer components include CPU, Memory Subsystem, and I/O Subsystem.
• Data Bus carries data between components.
• Address Bus specifies memory locations.
• Control Bus manages control signals.
• I/O Subsystem consists of I/O Devices.

Computer Architecture

• Encompasses system attributes that directly impact the logical execution of programs.
• It defines what the system can do, visible to the programmer.
• Deals with 'What to do?' in computer design.
• Provides functional details and behavior of a computer system.
• Serves as a blueprint for design and implementation.
• It includes instruction set, number of bits for data types, I/O mechanisms, and memory addressing techniques.

Main Components of a Computer

• Modern computer designs are based on concepts by John von Neumann.
• A computer consists of CPU (central processing unit), memory, and I/O components.
• Data and instructions are stored in a single read-write memory unit.
• Memory contents are addressable by location, regardless of data type.
• Execution occurs sequentially unless modified by an instruction.
• The CPU contains an arithmetic and logic unit, registers, and control circuits for instruction handling.
• Memory stores instructions and data, known as Random-Access Memory (RAM).
• The Input/Output Processor (IOP) manages communication between the computer and the external world.

System Components

• Primary system components: CPU/Microprocessor, Memory Subsystem, and I/O Subsystem.

System Buses

• Consists of Address Bus, Data Bus, and Control Bus.

Instruction Cycle

• Involves Fetch, Decode, and Execute stages.

Jhon von Neumann Architecture

• Instructions and data are mixed in memory.
• Commonly used in modern computers.
• All memory can store program elements, data, and instructions.

Harvard Architecture

• Instructions and data are stored separately.
• Used in low-level cache memory design
• The memory is divided into two separate memories, one for data and one for instructions.

Computer Organization

• The operational units and their interconnections that realize the architectural specifications.
• Implements the provided computer architecture.
• Focuses on 'How to do?' in computer design.
• Includes hardware details transparent to the programmer.
• Consisting of control signals, interfaces, and memory technology.
• Organizational aspects include the inclusion of a multiply instruction and its implementation.

Architecture & Organization

• Computer manufacturers offer families of models with the same architecture but different organization.
• Different models in a computer family vary in price and performance despite using the same architecture.
• An architecture can span many years and models, with the organization changing with technology.

Architecture vs Organization

• Computer architecture explains what a computer should do.
• Computer organization explains how a computer works.
• Architecture provides functional behavior.
• Organization provides structural relationships between computer parts.
• Architecture involves high-level, conceptual design.
• Organization involves low-level, more detailed design.
• Architecture design comes first, guiding organization.
• Computer organization starts after architecture is finalized.

Structure & Function

• A computer is a complex system with millions of electronic components.
• It’s easier to describe it from the top down.
• This begins with major components and proceeds to successively lower layers.
• Structure is the way components relate to each other.
• Function is the operation of individual components as part of the structure.

Function (in computers)

• All computer functions include: data processing, data storage (temporary or permanent), data movement (between the computer and the outside world), and control (of the other three functions).

Functional View

• It involves the operating environment (source and destination of data).
• Data Movement Apparatus handles movement of data.
• Control Mechanism oversees the other functions.
• Data Storage Facility holds data.
• Data Processing Facility manipulates data.

Operations

• Data movement involves control between storage, processing, and movement.
• Storage involves control between storage and movement.
• Processing from/to storage involves control between storage and processing.
• Processing involves control from storage to I/O with movement.

Structure - Top Level

• It consists of peripherals, central processing unit, and communication lines.
• Computer contains the central processing unit, main memory, systems interconnection, and input/output.

Structure - The CPU

• Internally, includes registers, arithmetic and logic unit, internal CPU interconnection, and control unit.

Structure - The Control Unit

• Includes sequencing logic, control unit registers and decoders, and control memory.

Summary

• Computer organization addresses control signals, signaling methods, and memory types.
• Encompasses physical aspects of computer systems.
• Deals with how a computer works.
• Computer architecture focuses on the structure and behavior of the computer system.
• Refers to logical system implementation as seen by the programmer including instruction sets, instruction formats, data types, and addressing modes.
• Deals with how to design a computer.