1.0 PC Hardware

1.2 Differentiate between motherboard components, their purposes, and properties.

The motherboard is the main integrated circuit board (ICB) within a computer. Also referred to as the main board or mobo for short, it is the primary interface for all of the other components in a computer. All of the other components must comply to certain specifications and guidelines in order to function properly with each specific motherboard.

  • Sizes

    A components form factor defines it's physical diminsions and characteristics. As a general rule, the form factor of a computer's components, the case, power supply, and motherboard, must all match.

    • ATX

      The ATX (Advanced Technology eXtended) was introduced by Intel in 1995 and remains the most popular form factor in a desktop configuration today. It utilizes a soft power switch, PS/2 keyboard & mouse connectors, and relocated components for better air flow and easier access. A full ATX board is 12" x 9.6" (305mm x 244mm).

      The ATX boards usually have a mouse, keyboard, USB, serial, parallel, video and audio connectors mounted in a standard position at the rear of the case.

      The original ATX power supply used a keyed 20-pin connector. Pentium 4 and Athlon 64 systems usually require an extra 4-pin 12V cable and 8-pin tertiary connector. Motherboards featuring PCI Express require an extended 24-pin PSU connector in addition to the 12V cable.

    • Micro-ATX

      The micro ATX form factor was introduced in 1996 and quickly became popular as a replacement for the ATX as a desktop unit with a smaller footprint. The micro ATX motherboard measured 9.6" x 9.6" (244mm x 244mm) but still provided all of the basic functions of the full ATX board.

      The smaller motherboard also allowed for a savings in associated costs due to a reduction in the number of expansion slots and a reduced-output power supply.

    • ITX

      Mini-ITX is a 17×17 cm (or 6.7×6.7 inches) low-power motherboard form factor developed by VIA Technologies in 2001. Mini-ITX is significantly smaller than microATX but remains screw-compatible with that format. Mini-ITX boards can often be passively cooled due to their low power consumption architecture.

  • Expansion slots

    An expansion slot is an electrical connector on a computer motherboard or riser card that is designed to add functionality or increase the functionality of a computer system via the expansion bus.

    Common examples of expansion slots include ISA (Industry Standard Architecture), AGP (Accelerated Graphics Port), PCI (Peripheral Components Interconnect), and PCI Express. Laptop or notebook computers are generally designed to accept the CardBus, PC card, or PCMCIA technologies which were later replaced by the ExpressCard versions.

    • PCI

      • Peripheral Component Interconnect
      • Commonly used for network, modem, sound, and graphics adapters
      • Supports bus speeds of 33MHz and 66 MHz
      • Supports 32-bit and 64-bit bus

    • PCI-X

    • PCIe

      • Peripheral Component Interconnect Express
      • PCI Express (PCIe) is an I/O bus technology that is replacing Peripheral Component Interconnect (PCI), PCI-X, and the Accelerated Graphics Port (AGP). PCIe hardware is backwards compatible with PCI software on Microsoft Windows operating systems.
      • Supports bus speeds of either 33MHz or 66 MHz
      • Supports 32-bit and 64-bit bus widths
      • Designed to replace PCI and AGP bus standards

    • miniPCI

    • CNR

      A Communications and Networking Riser, designed to provide audio, networking, or modem functionality on a CNR card. Nearly all riser technologies, such as ACR, AMR, and CNR, have been generally obsoleted in favor of on-board or embedded components.

    • AGP2x, 4x, 8x

      The AGP (Accelerated Graphics Port) is a high-speed point-to-point channel for attaching a single graphics card to a computers motherboard, primarily to assist in the acceleration of 3D computer graphics. AGP provides a direct connection between the video adapter and the CPU but has been replaced by PCI-Express technology.

      AGP versions include:

      • AGP 1.0 - 3.3 volts signaling with speed multipliers 1x (267MB/s), 2x (533MB/s)
      • AGP 2.0 - 1.5 volts signaling with speed multipliers 1x (267MB/s), 2x (533MB/s), 4x (1067MB/s)
      • AGP 3.0 - 0.8 volts signaling with speed multipliers 4x (1067MB/s), 8x (2133MB/s)

  • RAM slots

  • CPU sockets

    A CPU socket or slot is a mechanical component, mounted permanantly on the motherboard, that provides mechanical and electrical connections between a microprocessor and a printed circuit board (PCB). It is designed to accomodate specific processor packages and allow the CPU to be replaced without soldering.

  • Chipsets

    The chipset typically refers to a group of integrated circuits designed to provide a means of communication between the CPU and other components and peripherals found throughout the computer.

    • North Bridge

      • Memory Controller Hub
      • Controls communication between the CPU, Ram, and video controller

    • South Bridge

      • I/O Contruller Hub
      • Provides a communication path between the Northbridge and the expansion bus and peripherals

    • CMOS battery

      The memory and real-time clock are generally powered by a 3 volt CR-2032 lithium coin cell battery. These cells typlcally last two to ten years before needing replacement. When replacing the cell, the system time and CMOS BIOS settings may revert to default values.

  • Jumpers

    Jumper settings, once used extensively in computers, are a mechanical means of setting configuration options.

  • Power connections and types

  • Fan connectors

  • Front panel connectors
    • USB

      Universal Serial Bus, hot-swappable, powered through the USB connection, USB A, USB B and USB mini-B connections.

    • Audio

      Mini-audio jack, 1/8" jack, 3.5mm jack.

    • Power button

    • Power light

    • Drive activity lights

    • Reset button

  • Bus speeds

    A computer bus is an electrical pathway through which the processor communicates with the internal and external devices attached to the computer. It connects all internal computer components to the main memory and the CPU. Some motherboards have multiple busses used for different functions.

    Each bus is defined by it's width (the number of bits of data that can be transferred at once), it's speed measured in cycles per second or megahertz (MHz), and refers to the amount of data that can move across the bus simultaneously.

    Width x speed = throughput

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