Computer Hardware and I/O Systems

Computer Hardware, Memory, and I/O

• Objectives:
  • Learn computer hardware components
  • Understand CPU, memory, and I/O device relationships
  • Differentiate storage device types and characteristics
  • Identify different input/output devices
• Computer Operations:
  • Accepts data and instructions via input
  • Stores data and instructions
  • Processes data based on instructions
  • Produces output
  • Controls all computer operations

PC Hardware Interaction

• Diagram shows the interaction between:
  • Input Unit
  • CPU (Central Processing Unit)
    • Registers
    • Control Unit (CU)
    • Arithmetic Logic Unit (ALU)
  • Output Unit
  • Memory Unit

Computer System Components

• Diagram shows:
  • Input Devices (e.g., keyboard, mouse, camera)
  • Output Devices (e.g., monitor, printer, speakers)
  • Central Processing Unit (CPU)
  • Main Memory (RAM)
  • Secondary Storage Devices (e.g., hard drive, SSD, CD/DVD)

Central Processing Unit (CPU)

• CPU (Microprocessor):
  • Brain of the computer
  • Most complex part
  • Example: Six-Core i7 / Eight-Core Xeon E5
  • 2,270,000,000 individual components
  • Plugged into the motherboard
  • Follows the "stored program" concept, data & instructions stored in memory

CPU Components

• Arithmetic and Logic Unit (ALU):
  • Performs arithmetic and logical operations.
• Control Unit (CU):
  • Supervises and coordinates processing of data & instructions.
  • List of all possible CPU functions is the "Instruction Set".
• Registers:
  • High-speed memory inside the CPU, temporarily stores data (processing/control).
  • Examples: Instruction register (IR), Program counter(PC)

Instruction Cycle

• Programs are broken down into simple commands (primitive operations), for example "Add two numbers".
• Instruction Cycle:
  • Fetch: CPU gets the instruction from memory.
  • Decode: CPU interprets the instruction.
  • Execute: CPU performs the required operation (e.g., arithmetic).

Memory Hierarchy

• Modern computers use a combination of memory types, each with its own performance and cost characteristics.
• CPU is much faster than memory.
• Memory is organized so the speed does not affect system performance.
  • Uses a limited amount of fast, but expensive memory.
  • Uses a larger amount of slow, but inexpensive memory.

Memory Unit

• Part of the computer that stores programs and data.
• Consists of cache memory and primary memory.
• Main Memory (Primary Memory):
  • Computers main storage area holding data and programs being used by the CPU.
• Random Access Memory (RAM):
  • Holds programs and data active in the computer.
• Read Only Memory (ROM):
  • Works with RAM to form primary memory.
• Secondary Memory:
  • Data & program storage that is permanent, non-volatile.

Memory Capacity (Size)

• Bits are building block units for digital memory.
• Memory is measured in bytes (1 byte = 8 bits).
• Groups of bytes form a word (e.g., 2, 4, or 8 bytes).
• Memory size measured in:
  • kilobytes (KB)
  • megabytes (MB)
  • gigabytes (GB)
  • terabytes (TB)
• Byte represents a character (e.g., letter). Megabyte is more than a million characters.

Cache Memory

• High-speed circuitry for fast data access.
• Holds recently used data in a small amount of megabytes.
• Placed between RAM & CPU
• Volatile (contents lost if power is off)

RAM (Random Access Memory)

• Operating system & apps load into RAM when started.
• Volital, meaning data erased when power is off
• Larger than cache memory
• Significantly cheaper to produce than cache memory
• Separate chips

ROM (Read Only Memory)

• Non-volatile, containing read-only software programmed by the manufacturer.
• BIOS chip (Basic Input/Output System):
  • Basic program the computer uses to work with the motherboard and operating system.
  • Power-On Self-Test (POST)
    • Checks hardware for proper operation during startup.
• Bootstrap loader
  • Loads operating system from disk to RAM.

CPU-Memory Interaction

• Diagram shows flow of data between CPU, RAM, and secondary storage.

Secondary Memory

• Main memory is expensive and volatile
• Secondary memory is cheap and non-volatile (stores data when power is off)
• Access time is slower than main memory.

Magnetic Hard Disk (HDD)

• Metal platters with magnetic medium, storing data as spots.
• Disk rotates, spots detected by sensor.
• Measured in GB or TB.
  • Divided into concentric rings (tracks) and sectors on each ring.
  • Sectors on the same radius form a cylinder.
  • Fragments of files—clusters—are stored in contiguous sectors.

Solid State Drive (SSD)

• Uses integrated circuits, typically using flash memory.
• More resistant to physical shock, runs silently, and has faster access times.
• Stores data in semiconductor cells.

Optical Disk Technologies

• Written & read by laser beams (not affected by magnetic fields).
• Slower than HDD.
• Include CD-ROM, CD-RW,DVD.
• Examples
  • CD-ROM (read only)
  • CD-RW (rewritable)
  • DVD

Flash Memory

• Non-volatile computer storage chip that is removable & reusable (via USB).
• Smaller, lighter, higher capacity (TB).
• Durable due to lack of internal moving parts.
• High speed, low energy consumption.

Buses

• Set of wires for interconnection in a system.
• System Bus (Internal Bus): Connects components (CPU, memory) on the motherboard.
• Expansion Bus(External Bus) Connects external components (peripherals),expansion slots, I/O ports and drive connections.
• Data bus: Transfers data between the CPU and memory.
• The bus width and speed affect computer speed.

System Bus

• Consists of three buses: address bus, data bus, and control bus
• Address Bus: Determines max number of locations computer can access.
• Data Bus: Transfers data between the CPU and memory.
• Control Bus: Controls all system functions.

Performance of a Computer

• Performance measured by factors like:
  • Registers
  • RAM
  • System Clock (measured in Hertz - one clock tick per second)
  • Bus Bandwidth
  • Cache Memory

Motherboard

• Large printed circuit board that connects all components (processor, memory, electronic devices).

Chipset

• A series of chips directly attached to the motherboard.
• Controls the system's functions and capabilities.
• All components communicate with the processor via the chipset.

CMOS Chip

• Saves system information (e.g., time, date, settings).
• Powered by a battery on the motherboard.

Expansion Slots

• Bus slots or expansion ports for adding video, fax/modem, network cards, memory slots for HD/CD drives to a computer.

Input/Output Devices

• Peripheral devices: I/O devices attached to the computer.
• Input Devices: Devices providing data/instructions to the computer.
• Output Devices: Devices conveying information from the computer.

Input Devices: Scanner

• Optical Input device that reads paper documents & converts the image into digital format for storage on the computer.
• Types: Hand-held, flat-bed.

Output Devices: Printer

• Print quality determined by resolution measured in dots per inch (dpi).
• Types: Impact (Dot Matrix, Daisy Wheel, Drum) and Non-impact (Laser, Inkjet).

Output Devices: Monitor/Screen

• Monochrome or color display monitors.
• Color support varies by adapter (e.g., SVGA).
• Types: CRT, LCD.
• Resolution: Number of pixels (dots) which measure clarity & sharpness.

Input/Output Devices: Touch Screen

• Accepts input when a user touches the screen.
• Used in ATM, information kiosks, etc.
• Types: Resistive, capacitive, surface wave.