Computer Architecture and Organization

Computer Architecture vs Computer Organization

• Computer architecture catalogs tools or attributes visible to users like instruction sets and addressing techniques.
• Computer organization defines system structuring for tool use, including ALU, CPU, memory, and its organization.
• Computer architecture is concerned with the way hardware components connect to form a system.
• Computer organization focuses on the structure and behavior of a system as seen by the user.
• Architecture acts as the interface between hardware and software; organization deals with components in a connection.
• Architecture helps understand system functionalities, while organization explains unit arrangement and interconnection.
• Programmers view architecture in terms of instructions, addressing modes, and registers.
• Organization expresses the realization of architecture.
• Computer architecture is considered first in design, serving as the basis for organization.
• Architecture involves high-level design issues, whereas organization deals with low-level design issues.
• Architecture involves logic, including instruction sets, addressing modes, data types, and cache optimization.
• Organization involves physical components like circuit design, adders, signals, and peripherals.

Evolution of Computing Devices

• ENIAC was the first computing system, designed in the early 1940s.
• ENIAC comprised 18,000 vacuum tubes, in 42 panels sized 9'x2'x1', arranged in a U-shape, with forced air cooling.
• ENIAC could perform 5,000 additions or 50 multiplications per second with a 100kHz clock speed, programmed via plugboard switches.
• The Atanasoff-Berry Computer (ABC) was the first digital electronic computer, though non-programmable
• ABC, designed in 1937 by John Vincent Atanasoff and Clifford E. Berry, solved systems of up to 29 simultaneous linear equations.
• Transistors were invented in 1947 at Bell Laboratories and are smaller and consume less power than vacuum tubes.
• Transistors act as electronic switches or gates, essential in modern telecommunications systems.
• Jack Kilby and Robert Noyce invented the integrated circuit concurrently; Noyce filed a patent in July 1959.
• In 1958, Jack Kilby invented the integrated circuit, revolutionizing electronics and enabling widespread cell phones and computers.
• Integrated circuits can function as amplifiers, oscillators, timers, logic gates, computer memory, microcontrollers, or microprocessors.
• In 1968, Robert Noyce co-founded Intel, which is still a global market leader in IC manufacturing, research, and development.
• Intel's first product, introduced less than a year after starting, was the 3101 static random-access memory (SRAM).
• SRAM is a type of random-access memory using latching circuitry to store each bit. it's volatile, losing data when power is off.
• Apple launched Lisa in 1983 as the first personal computer with a commercially sold graphical user interface (GUI).
• Lisa ran on the Motorola 68000, with dual floppy disk drives, a 5 MB hard drive, and 1MB of RAM.
• Lisa features included a drop-down menu bar, windows, multiple tasking, a hierarchical file system, cut/copy/paste, icons, folders, and a mouse.
• In 1990, Apple released the Macintosh Portable, weighing 7.3 kg (16 lb) and was extremely expensive.
• Apple’s first laptop product was the 16-bit lead-acid battery powered 7.2 kg (16 lb) Macintosh Portable.
• The Macintosh Portable pioneered the inclusion of a pointing device (trackball) in the laptop.
• In 1990, Intel introduced the Touchstone Delta supercomputer, featuring 512 microprocessors.
• The Intel Corp. built 512-processor Touchstone Delta marked a new era for scientific computing.
• This system provided enough computing for government and university researchers to pursue real-time satellite image processing and molecular models for AIDS research.

Functional Units of Digital System

• A computer organization details the functions and design of a digital system's units.
• A general-purpose computer system exemplifies a digital system, with other examples include telephone switching exchanges, digital voltmeters, digital counters, electronic calculators and digital displays.
• Computer architecture specifies the instruction set and hardware units that implement the instructions.
• Computer hardware consists of electronic circuits, displays, magnetic/optical storage, and communication facilities.
• Functional units are a part of a CPU that handles operations and calculations called for by the computer program. -Functional units within a CPU perform program operations and calculations, including input, processing, memory, arithmetic/logic, control, and output.
• Input units enable the computer to read data from devices like keyboards, mice, joysticks, trackballs, and microphones.
• The keyboard is a well-known input device.
• When keys are pressed, letters/digits are automatically translated into a corresponding binary code and sent to either memory or the processor.
• The Central Processing Unit (CPU) carries out instructions from computer programs, performing arithmetic, logical, control, and I/O operations.
• The Memory unit stores running programs and needed data, and is categorized into primary and secondary memory.
• Memory enables processors to access running applications and services temporarily stored at specific memory locations.
• Primary storage is the fastest memory, operating at electronic speeds, containing semiconductor storage cells. The word length of a computer is between 16-64 bits.
• Primary memory is volatile; data in RAM is lost when the computer shuts down.
• Cache memory, a fast memory type highly coupled with the processor, quickly fetches data.
• Common primary memory examples include RAM and ROM.
• Secondary memory stores large amounts of data/programs long-term and is non-volatile.
• Common secondary memory examples include magnetic disks, magnetic tapes, and optical disks.
• The Arithmetic & Logical Unit (ALU) executes arithmetic (addition, subtraction, multiplication, division) and logical (AND, OR, NOT) operations.
• The control unit coordinates the operation of the processor, directing memory, ALU, and I/O devices.
• Adding two operands ("Add LOCA, RO") involves adding memory location LOCA to the register RO and placing the sum in register RO.
• The control unit is the nerve center of a computer system.
• The output unit sends processed results in a way that the user can understand.
• Output devices generate information or any other response processed by the computer.
• The most common example of an output device is a monitor.

Basic Operational Concepts

• The key function of a computer system involves the ability to execute a program, or a sequence of instructions.
• These instructions are stored in computer memory.
• Executing instructions processes data already loaded in memory via input devices.
• After data processing, the result is stored for future reference or sent outside via an output port.
• Processors use registers for temporary data storage and include program counters (PC), instruction registers (IR), memory address registers (MAR), and memory data registers (MDR).
• The program counter is one of the most critical registers and monitors the execution of instructions.
• IR is used to hold an instruction that is currently being executed.
• The contents of IR are available to the control unit,.
• The control unit generates timing signals to control processing elements involved in instruction execution.
• The MAR and MDR handle data transfer between main memory and the processor.
• MAR holds the address of main memory for data transfer.
• MDR contains the data to be written into or read from the addressed word of main memory.
• Communication with devices is called "servicing" the devices.
• Processors service devices using either a polling routine or an interrupt.
• Polling lets software check input and output devices frequently to see if they need servicing.
• Interrupts provide external asynchronous input, so processors can finish current instructions and fetch routines to service a device.