Computer Systems Organization and Architecture

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Definition of a computer system

A combination of hardware and software components designed to process and manipulate data. Includes both physical and logical elements.

Scope of computer systems

Range from PCs and smartphones to supercomputers, embedded systems, and cloud computing; used in business, science, education, and entertainment.

Historical development - Mechanical computers

Example: Charles Babbage's Analytical Engine.

Historical development - Electromechanical computers

Example: IBM's Mark I.

Historical development - Vacuum tube computers

Example: ENIAC.

Historical development - Transistor computers

Example: UNIVAC.

Historical development - Integrated circuit computers

Example: Intel 4004; microcomputers like IBM PC.

Historical development - Personal computers

Example: Macintosh, Windows PC.

Basic component: CPU

Executes instructions and performs calculations; fetches data and instructions from memory.

Basic component: Memory (RAM & ROM)

RAM is volatile temporary storage; ROM stores essential firmware and is non-volatile.

Basic component: Input/Output (I/O) devices

Enable communication with external world; e.g., keyboard, mouse, display, printer.

Basic component: Storage devices

Long-term storage such as HDDs, SSDs, and optical drives.

Basic component: Motherboard

Main circuit board housing CPU, memory, and connections.

Basic component: Power supply

Converts electricity from outlet into usable voltages for computer components.

Von Neumann Architecture - CPU

Fetches, decodes, executes instructions, and stores results.

Von Neumann Architecture - Memory

Stores both instructions and data in the same RAM.

Von Neumann Architecture - Control Unit

Manages execution sequence of instructions.

Von Neumann Architecture - ALU

Performs arithmetic and logical operations.

Von Neumann Architecture - I/O

Handles data exchange with external world.

Memory hierarchy definition

Organizes memory types by speed, cost, and capacity for efficient data access.

Memory type: RAM

Volatile, fast, limited capacity, stores data and program code needed during operation.

Memory type: ROM

Non-volatile, permanently stores firmware and essential instructions.

Memory type: Cache

Small, high-speed memory between CPU and RAM, stores frequently used data.

Memory type: Secondary storage

HDDs, SSDs; high capacity, slower than RAM, used for OS, apps, and user files.

CPU component: Control Unit

Manages instruction fetching, decoding, and execution.

CPU component: ALU

Performs arithmetic and logic operations.

CPU component: Registers

Small, fast memory for temporary data storage.

CPU component: Cache

Stores frequently accessed data for quick retrieval.

CPU component: Clock generator

Controls timing of CPU operations.

Pipelining

Breaks instruction execution into stages; multiple instructions overlap to increase throughput.

Superscalar

Executes multiple instructions simultaneously using multiple ALUs.

Parallel processing

Execution of multiple tasks simultaneously to improve performance.

Multi-core processors

Single chip with multiple cores executing independently; improves multitasking and performance.

Benefits of multi-core processors

Enhance multitasking, speed up parallelizable tasks, and reduce power consumption.

Clock cycles

Each cycle corresponds to one basic CPU operation.

Clock speed

Measured in Hertz (Hz); number of cycles per second.

Execution time

Product of number of cycles × duration per cycle; reduced by smaller cycles or efficient instructions.