1.0 Hardware

1.2 Explain motherboard components, types and features

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.

  • Form Factor

    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 / BTX

      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.

      The BTX (Balanced Technology eXtended) form factor was intended to replace the ATX. The layout of the board offered better airflow than the ATX, but the BTX form factor was never fully accepted by the industry.

    • 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.

    • NLX

      The NLX (New Low-profile eXtended) form factor, now considered an almost osolete technology, was a low-profile inexpensive PC, designed for mass marketing that implemented the use of a daughterboard to house expansion adapters and supported the new AGP (Accellerated Graphics Port).

  • I/O interfaces

    I/O interface or ports refers to the physical connection between the computer and any attached device or communication circuit. These interfaces are generally located on the back of the computer or the front panel. These connections generally provide an electrical circuit for power, and the means of transferring data. A different interface is required for each type of I/O device or connection and must follow specific standards for that connection.

    • Sound

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

    • Video

      • VGA - Video Graphics Array DC-15 connector
      • DVI - Digital Video Interface
      • S Video
      • HDMI - High Definition Multimedia Interface

    • USB 1.1 and 2.0

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

    • Serial

      • Typical serial ports include 9-pin and 25-pin connection
      • Compliant to the RS-232 standard
      • Information is transfered in or out in a single-bit stream
      • Newer technology includes Ethernet, FireWire, and USB

    • IEEE 1394 / Firewire

      • 1394a - 400MB/s
      • 1394b - 800MB/s

    • Parallel

      Also known as a printer or Centronics port, a 25-pin computer interface designed for bi-directional communication. Defined under the IEEE 1284 standard.

    • NIC

      • Network Interface Controller
      • Provides communication between the computer and the network
      • Modern onboard interface is typically an RJ-45 connection

    • Modem

      Acronym for modulator-demodulator. Provides analog phone line communication between the computer and a telephone network. Interface is provided through an RJ-11 connection with 56Kb/s maximum transmission speed.

    • PS/2

      Also refered to as a mini-DIN connection, this smaller version of the DIN connection is commonly used to connect the keyboard or mouse.

  • Memory slots

    Memory types have changed through the years, driven by standardization and technology. It is one of the most important components of your computer, but differs somewhat with each motherboard.

    • RIMM

      Rambus In-line Memory Module (RIMM) slots were first introduced as a proprietary standard on the Intel Pentium 3 motherboard by Rambus, Inc. in the mid 1990s, but the technology quickly fell from favor as a result of the higher expense.

      Rambus Dynamic Random Access Memory (RDRAM) modules are double data rate memory, transfering data on both the rising and falling of the clock cycle and measured 133mm x 35mm in size with a 16-bit, 184 pin and a 32-bit, 232 pin form factor.

      Computers that support RIMM require all of the memory slots to be filled. Empty slots must be filled with either another RIMM module or a Continuity RIMM (C-RIMM) pass through module for 16-bit systems or a Continuity and Termination RIMM (CT-RIMM) for a 32-bit system to allow a continuous signal.

    • DIMM

      Dual In-line Memory Modules began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as Intel's Pentium processors began to gain in popularity. The primary difference between SIMMs and DIMMs is that DIMMs have separate electrical contacts on each side of the module, while opposing contacts on SIMMs are connected. Standard DIMMs have a 64-bit data path and come in three common pin configurations.

      • 168-pin slots - for SDRAM memory commonly found in Pentium and Athlon systems
      • 184-pin slots - for DDR SDRAM memory for desktop computers
      • 240-pin slots - for DDR2 and DDR3 SDRAM memory for desktop computers

      SDRAM modules have two notches on the bottom edge, DDR SDRAM modules have one.

    • SODIMM

      SODIMMs (Small Outline Memory Modules) are a smaller alternative to a DIMM, being roughly half the size (68mm x 32mm) of regular DIMMs. SO-DIMMS are commonly used in systems which have space restrictions such as notebooks, small footprint PCs, high-end upgradable office printers, and networking hardware like routers.

      • 72-pin slots - 32-bit data path, now obsolete
      • 100-pin slots - 32-bit data path, two notches
      • 144-pin slots - 64-bit data path, single notch near the center
      • 200-pin slots - 64-bit data path, single notch nearer to one side
      • 204-pin slots - 64-bit data path, single notch nearer to one side

    • SIMM

      Single In-line Memory Module containing RAM used in computers in the 80's and late 90's. Contacts on both sides of the module were the same. Early 30-pin modules transferred 8 bits of data at a time and usually had either 256KB or 1MB of memory. Later, a wider SIMM was developed with a 72-pin configuration, which could supply 32 bits of data at a time. The 72-pin SIMMs are 3/4 of an inch longer than the 30-pin SIMMs and have a single notch near the middle of the contacts.

      Note: Not all SIMMs follow the same standard.

  • Processor sockets

    • The interface that connects the processor to the motherboard.
    • Mounted permanantly on motherboard
    • Designed to accomodate specific processor packages

  • Bus architecture

    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

    - More Information -

    • Address Bus

      The address bus (or memory bus) transports memory addresses the processor wants to access in order to read or write data. It is a unidirectional bus.

    • Data Bus

      The data bus is bidirectional and transfers instructions coming from or going to the processor.

    • Control Bus

      The control bus (or command bus) is a bidirectional bus that carries commands from the CPU and returns status signals from the hardware devices within the system.

    • Internal Bus

      The internal bus or front-side bus (FSB) allows the processor to communicate with the system's central memory (RAM).

    • Expansion Bus

      The expansion bus (input/output bus) allows expansion devices to communicate with the rest of the system.

  • Bus slots

    • 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

    • AGP

      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)

    • 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

    • AMR

      An Audio Modem Riser (AMR) expansion slot is often found on the motherboards of some Pentium III, Pentium 4, and Athlon personal computers, designed to provide analog functionality on an expansion card.

    • 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.

    • PCMCIA

      Acronym for and developed by the Personal Computer Memory Card International Association, designed as expansion devices for laptop computers. A PCMCIA card is correctly referred to as a PC Card (16 bit) or CardBus (32 bit), though the PC Card is now considered legacy. The most common form factors include types I, II, and III and are now used as interfaces for several expansion options, including hard drives, networking, USB devices and more.

      • Type I - 16-bit, 3.3 mm thick
      • Type II - 16-bit or 32-bit, 5.0 mm thick
      • Type III - 16-bit or 32-bit, 10.5 mm thick

      PCMCIA Tutorial

  • PATA

    Parallel ATA, sometimes refered to as Ultra ATA or IDE, transfers data in parallel at the rate of 133MB per second. Up to two drives can be connected to the motherboard per controller port (4 max), through the use of either a 40 or 80 wire cable connected to a 40-pin connector on the back of the drive.

    • IDE

    • EIDE


    • Standard defines a seven conductor data cable with a 15 pin power connector
    • Suplied voltages include 3.3 V, 5 V, and 12 V

  • Contrast RAID (levels 0, 1, 5)

    RAID is an acronym for Redundant Array of Independent/Inexpensive Disks. There are 3 levels of RAID addressed on the 220-70x A+ exam series, RAID 0, 1, and 5. RAID Level 10 has since been added to the 220-80x series exam. Not all levels of RAID provide the same level of redundancy. Hardware based RAID provides better performance over software based RAID.

    This topic is also open for discussion in our forum.

    1. RAID Level 0: Disk striping without parity or mirroring
      • Splits data evenly across two or more drives
      • Provides improved performance
      • Has zero redundancy
      • Provides no fault tolerance

    2. RAID Level 1: Disk mirroring
      • Mirroring without parity or striping
      • Requires at least two drives
      • Data is written identically to multiple drives
      • Continues to operate as long as at least one drive is functioning
      • Can increase read performance

    3. RAID Level 5: Disk striping with parity
      • Requires at least three drives
      • Data is distributed across all disks
      • Requires all drives but one to operate

    4. RAID Level 10: Disk striping with mirroring
      • Requires four drives
      • Data is written identically to multiple drives
      • Continues to operate as long as at least one drive is functioning
      • Provides better throughput and latency

  • Chipsets

    • Northbridge

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

    • Southbridge

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

  • BIOS / CMOS / Firmware

    The BIOS (Basic Input/Output System) is a special software that handles the basic interface between the operating system and the major hardware components of your computer. The BIOS contains the necessary code required to control the keyboard, display screen, disk drives, serial communications, and a number of other functions.

    On start-up, the BIOS performs several tasks. It will first read the CMOS Setup for any configuration instructions specific to the unit. It will also load device drivers, perform the power-on self-test (POST), and initiate the boot sequence.

    Configuration settings for the BIOS are usually stored on a Flash memory chip on the motherboard, often called a ROM BIOS, and retains this information when the unit is powered down. This ensures that the BIOS will always be available and not damaged by disk failures. The BIOS can be accessed directly at startup by pressing DEL or a function key (usually F2). Inexperienced users should not make changes to the BIOS settings.

    CMOS (Complementary Metal-Oxide-Semiconductor) is an on-board, battery powered semiconductor chip used inside computers to store information such as the system time, date, and the system hardware settings.

    If the battery that provides power to your CMOS RAM fails, this information is lost, and the system boots with the default settings.

    • POST

      The Power On Self Test is a function of the motherboards BIOS. It refers to routines which run immediately after an electronic device is powered on and set an initial value for the device's state. These routines are part of a device's pre-boot sequence. Once POST completes successfully, bootstrap loader code is invoked.

    • 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.

  • Riser card / daughterboard

    A daughterboard or riser is a circuit board that serves as an extension to the motherboard by allowing expansion cards to fit on their side, parallel to the motherboard, usually to maintain a small or slim form factor. Daughterboards will often have sockets or connectors for additional expansion boards and will usually have only internal connections and access the motherboard directly.