1.2 Explain motherboard components, types and features

1.2 Explain motherboard components, types and features

A motherboard, also known as a mainboard, logic board, or system board, and sometimes abbreviated as mobo, is the central or primary circuit board of the computer. A typical computer is built with the microprocessor, main memory, and other basic components on the motherboard. Other components of the computer such as external storage, control circuits for video display and sound, and peripheral devices are typically attached to the motherboard via ribbon cables, other cables, and power connectors.

Form Factor

Form factor refers to the size and format of motherboards

  • ATX (Advanced Technology Extended) is a full size board measuring 12" wide by 9.6" deep (305 mm x 244 mm)
  • microATX is a small motherboard size of 9.6" x 9.6" (244 mm x 244 mm). Compared to full size ATX, microATX has reduced the amount of I/O slots but a smaller power supply can be used.
  • NLX (New Low Profile Extended) was a form factor proposed by Intel and developed jointly with IBM, DEC, and other vendors for low profile, low cost, mass-marketed retail PCs. Release 1.2 was finalized in March 1997 and release 1.8 was finalized in April 1999. NLX was similar in overall design to LPX, including a riser card and a low-profile slimline case. It was modernized and updated to allow support for the latest technologies while keeping costs down and fixing the main problems with LPX.

    Many slimline systems that were formerly designed to fit the LPX form factor were modified to fit NLX. NLX is a true standard, unlike LPX, making interchangeability of components easier than it was for the older form factor. IBM, Gateway, and NEC produced a fair number of NLX computers in the late 1990s, primarily for Socket 370 (Pentium II-III and Celeron), but NLX never enjoyed the widespread acceptance that LPX had. Most importantly, one of the largest PC manufacturers, Dell decided against using NLX and created their own proprietary motherboards for use in their slimline systems. Although many of these computers and motherboards are still available secondhand, new production has essentially ceased, and in the slimline and small form factor market, NLX has been superseded by the Micro-ATX, FlexATX, and Mini-ITX form factors.

Common Motherboard Layout (INTEL Socket T (LGA775)


1 CPU Socket

2 CPU_FAN - CPU cooling fan connector

3 DIMM1~2 - 240-pin DDR2 SDRAM slots

4 IRDA - Infrared header

5 FDD - Floppy diskette drive connector

6 ATX1 - Standard 24-pin ATX power connector

7 IDE1 - Primary IDE channel

8 CLR_CMOS - Clear CMOS jumper

9 SATA1~4 - Serial ATA connectors

10 PANEL1 - Panel connector for case switches and LEDs

11 USB1-2 - Front Panel USB headers

12 1394a - IEEE 1394a header

13 BIOS_WP - BIOS flash protect jumper

14 COM2 - Onboard Serial port hader

15 WOL1 - Wake On LAN connector

16 S/PDIF - SPDIF out header

17 F_AUDIO - Front panel audio header

18 AUX_IN - Auxiliary In connector

19 PCI1~2 - 32-bit add-on card slots

20 PCIE1 - PCI Express x1 slot

21 PCIEX16 - PCI Express slot for graphics interface

22 SYS_FAN - System cooling fan connector

23 ATX12V - Auxiliary 4-pin power connector

I/O interfaces

Integrated AMD Motherboard

I/O interfaces

PS2 Mouse Used to connect a PS/2 pointing device.

PS2 Keyboard Used to connect a PS/2 keyboard.

VGA Port Connect your monitor to the VGA port.

DVI-I Port Connect a monitor with DVI connection.

HDMI Connect a monitor or HDTV with HDMI connection.

Optical S/PDIF Used for sound connections to home audio recievers or powered PC speakers with optical connections.

1394a Port Use the 1394a port to connect to any firewire device.

LAN Port Used to connect an RJ-45 cable to a Network hub or router.

USB Ports Used to connect USB devices such as printers, scanners cameras et...

Analog Audio Ports Used to connect audio devices.

  • Orange - Center & Woofer
  • Black - Back Surround
  • Grey - Side Surround
  • Blue - Line-in
  • Green - Front Out
  • Pink - Mic_in Rear

Memory slots

RIMM - Were commonly used on the Intel Pentium 4 motherboards. Unlike most other types of computer memory, computers that support RIMM require a continuous signal. If a memory slot is left empty the PC will not work. The empty slot must be filled with another RIMM module or a C-RIMM pass through module which enables a continuous signal.

DIMM - Come in three common pin configurations.

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

< Installed DIMM

< Open DIMM Slots


Small outline dual inline memory module. Smaller and thinner than standard DIMMs, SODIMMs are typically used in laptop computers.

The most common current laptop memory is the Small Outline Dual In-line Memory Module. The cards are 5cm long by 2.5cm tall, or about 2x1 inch.

Where SODIMMS can differ is in the number of pins that connect to the computer's bus; the more pins, the wider the pathway for data, and higher the potential speed.SODIMMs have identifying notches along the pin end of the module that prevent installation of the wrong type of memory in a slot.

Speed Clock Rate Data Rate
PC2-3200 100MHz 400MT/s
PC2-4300 133MHz 532MT/s
PC2-5300 167MHz 667MT/s
PC2-5400 167MHz 667MT/s
PC2-6200 200MHz 800MT/s


Single inline memory module. A high-density DRAM package alternative consisting of several components connected to a single printed circuit board.

Processor sockets

A motherboard is designed for a certain range of processors. One of the determining factors of processor compatibility is the slot or socket connector soldered onto the board. 242-contact and 330-contact slot connectors were used for a short time to allow for L2 cache to be packaged close to the processor die. Processor manufacturing advancements now allow L2 cache to be manufactured on the same die as the processor, requiring a smaller form-factor processor packaging. PGA (pin grid array) sockets are more common, flexible, and compact, but have many variations in the amount of pin connects and pin layouts.

CPU Socket Processors PIN's
Socket A AMD Athlon (650 MHz - 1400 MHz)

AMD Athlon XP (1500+ - 3200+)

AMD Duron (600 MHz - 1800 MHz)

AMD Sempron (2000+ - 3300+)

AMD Athlon MP (1000 MHz - 3000+)
Socket 754 AMD Athlon 64 (2800+ - 3700+)

AMD Sempron (2500+ - )

AMD Turion 64 (ML and MT)
Socket 939 AMD Athlon 64 (3000+ - 4000+)

AMD Athlon 64 FX

AMD Athlon 64 X2

Some AMD Opteron 1xx series

Some Sempron 3xxx


Socket 940

NOT compatible with Socket AM2 940 pin CPUs
AMD Athlon 64 FX

AMD Opteron
Socket AM2 Athlon 64

Athlon 64 X2

Athlon 64 FX





Socket AM3

Athlon 64

Athlon 64 X2

Athlon 64 FX

CPU Socket Processors PIN's
Socket 478 Intel Pentium 4 (1.4 - 3.4 GHz)

Intel Celeron (1.7 - 3.2 GHz)

Celeron D (to 3.2 GHz)

Intel Pentium 4 Extreme Edition (3.2, 3.4 GHz)
Socket 479 Intel Pentium M (900 MHz - 2.267 GHz)

Intel Celeron M (800 MHz - 1.733 GHz)

Intel Core Duo (1.667 - 2.167 GHz)

Intel Core Solo (1.667 GHz)

VIA C7-M (1,5 GHz and 1,8 GHz)
LGA775 Intel Pentium 4 (2.66 - 3.80 GHz)

Intel Celeron D (2.53 - 3.46 GHz )

Intel Pentium 4 Extreme Edition

(3.20 - 3.73 GHz)

Intel Pentium D (2.66 - 3.60 GHz)

Intel Pentium Extreme Edition

(3.20 - 3.73 GHz)

Intel Core 2 Duo (1.60 - 2.67 GHz)

Intel Core 2 Extreme (2.66 - 2.93 GHz)
Socket M Intel Core Solo

Intel Core Duo

Intel Dual-Core Xeon (1.67, 2.0)

Intel Core 2 Duo (T5x00, T7x00)

Bus architecture

Front side buses serve as a backbone between the CPU and a chipset. The chipset (northbridge and a southbridge) is the connection point for all other buses in the system. The PCI, AGP, and memory buses all connect to the chipset to allow for data to flow between the connected devices

Bus slots

PCI: Peripheral Component Interconnect, is a specification introduced by Intel Corporation that defines a local bus system that allows up to 10 PCI-compliant expansion cards to be installed in the computer. Many netword, modem, sound, and graphics adapters et... use the PCI bus.

The PCI bus is being replaced by PCI Express

AGP: Accelerated Graphics Port , used for graphics adapters. The AGP port is being replaced by the new PCIe slot.

PCIe: PCI Express (PCIe) is a new I/O bus technology that, over time, will replace Peripheral Component Interconnect (PCI), PCI-X, and the Accelerated Graphics Port (AGP). PCIe hardware is backwards compatible with PCI software (not with hardware PCI slots) on the Microsoft Windows 2000 and Microsoft Windows XP operating systems.

The PCI features supported by current Windows operating systems will continue to work with PCIe without any need for modifications in the applications, drivers, or operating system; however, the advanced PCIe features will be natively supported only in Windows Vista and later versions of Windows.

PCIe slots today are mostly used for graphics cards which require the greater bandwidth PCIe is capable of.

AMR: Audio Modem Riser, is an expansion slot found on the motherboards of some Pentium III, Pentium 4, and Athlon personal computers. Drawbacks of AMR are that it eliminates one PCI slot, it is not plug and play, and it does not allow for hardware accelerated cards (only software-based).

CNR: Communications and Networking Riser, is a slot found on some motherboards. A motherboard manufacturer can choose to provide audio, networking, or modem functionality in any combination on a CNR card.

Today nearly all riser technologies, such as ACR, AMR, and CNR, have been generally obsoleted in favor of on-board or embedded components.


eide connection

In 2003, the original ATA (Advanced Technology Attachment) was retroactively renamed Parallel ATA (PATA)

IDE: Integrated Drive Electronics

EIDE: Enhanced IDE, sometimes referred to as Fast ATA or Fast IDE

Are standard interfaces for connecting storage devices such as hard disks and CD-ROM drives inside personal computers.



SATA: Serial ATA (Advanced Technology Attachment) is a computer bus technology primarily designed for transfer of data to and from hard disks and optical drives. The SATA connectors will only fit in one orientation.

The main differences between the serial interconnect and the parallel interconnect of ATA are as follows:

  • Serial ATA is point to point, meaning only one storage device can be connected to a single Serial ATA cable. Parallel ATA has a shared channel and can connect up to two storage devices on a single cable.
  • Serial ATA is faster. Currently Serial ATA transfers data at a rate of 150 megabytes (MB) per second and will likely advance to 300 MB and 600 MB per second in the near future.
  • Serial ATA has a thinner cable and a smaller connection that is keyed so they cannot be connected incorrectly, unlike some parallel ATA cables.


Aimed at the consumer market, eSATA enters an external storage market already served by the USB and FireWire interfaces. Most external hard-disk-drive cases with FireWire or USB interfaces use either PATA or SATA drives and "bridges" to translate between the drives' interfaces and the enclosures' external ports, and this bridging incurs some inefficiency. Some single disks can transfer 131 MB/s during real use, more than twice the maximum transfer rate of USB 2.0 or FireWire 400 (IEEE 1394a) and well in excess of the maximum transfer rate of FireWire 800, though the S3200 FireWire 1394b spec reaches ~400 MB/s (3.2 Gbit/s). Finally, some low-level drive features, such as S.M.A.R.T., may not operate through USB or FireWire bridging. eSATA does not suffer from these issues. USB 3.0's 4.8Gbit/s and Firewire's future 6.4Gbit/s will be faster than eSATA I, but the eSATA version of SATA III will operate at 6.0Gbit/s, thereby operating at negligible differences of each other.

HDMI, Ethernet, and eSATA ports on a Sky+ HD Digibox

eSATA can be differentiated from USB 2.0 and FireWire external storage for several reasons. As of early 2008, the vast majority of mass-market computers have USB ports and many computers and consumer electronic appliances have FireWire ports, but few devices have external SATA connectors. For small form-factor devices (such as external 2.5-inch disks), a PC-hosted USB or FireWire link supplies sufficient power to operate the device. Where a PC-hosted port is concerned, eSATA connectors cannot supply power, and would therefore be more cumbersome to use.

Owners of desktop computers that lack a built-in eSATA interface can upgrade them with the installation of an eSATA host bus adapter (HBA), while notebooks can be upgraded with Cardbus or ExpressCard versions of an eSATA HBA. With passive adapters the maximum cable length is reduced to 1 metre (3.3 ft) due to the absence of compliant eSATA signal-levels.

Contrast RAID (levels 0, 1, 5)

Raid (redundant array of inexpensive disks) is now used as an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disk drives. The different schemes/architectures are named by the word RAID followed by a number, as in RAID 0, RAID 1, etc. RAID's various designs involve two key design goals: increase data reliability and/or increase input/output performance. When multiple physical disks are set up to use RAID technology, they are said to be in a RAID array. This array distributes data across multiple disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes.

  • RAID 0 (striped disks) distributes data across multiple disks in a way that gives improved speed at any given instant. If one disk fails, however, all of the data on the array will be lost, as there is neither parity nor mirroring. In this regard, RAID 0 is somewhat of a misnomer, in that RAID 0 is non-redundant. A RAID 0 array requires a minimum of two drives. A RAID 0 configuration can be applied to a single drive provided that the RAID controller is hardware and not software (i.e. OS-based arrays) and allows for such configuration. This allows a single drive to be added to a controller already containing another RAID configuration when the user does not wish to add the additional drive to the existing array. In this case, the controller would be set up as RAID only (as opposed to SCSI only (no RAID)), which requires that each individual drive be a part of some sort of RAID array.
  • RAID 1 mirrors the contents of the disks, making a form of 1:1 ratio realtime backup. The contents of each disk in the array are identical to that of every other disk in the array. A RAID 1 array requires a minimum of two drives. RAID 1 mirrors, though during the writing process copy the data identically to both drives, would not be suitable as a permanent backup solution, as RAID technology by design allows for certain failures to take place.
  • RAID 5 Striped set with distributed parity or interleave parity. Distributed parity requires all drives but one to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive. A single drive failure in the set will result in reduced performance of the entire set until the failed drive has been replaced and rebuilt.


The motherboard chipset consists of a north bridge, or Memory Controller Hub (MCH), which is responsible for controlling communication between system memory, the processor, AGP, and the south bridge, or I/O Controller Hub (ICH). The ICH controls communication between PCI devices, system management bus, ATA devices, AC'97 (audio), USB, IEEE1397 (firewire), and LPC controller. These chipsets are soldered onto the motherboard and cannot be changed or upgraded.

BIOS / CMOS / Firmware

Basic input/output system (BIOS) is the set of essential software routines that test hardware at startup, start the operating system, and support the transfer of data among hardware devices. The BIOS is stored in read-only memory (ROM) so that it can be executed when you turn on the computer. Although critical to performance, the BIOS is usually invisible to computer users.

The BIOS Setup Utility displays the PC system’s configuration status and provides you with options to set system parameters. The parameters are stored in battery-backed-up CMOS RAM that saves this information when the power is turned off. When the system is turned back on, the system is configured with the values you stored in CMOS.

Most BIOS Setup Utilities enable you to configure:

  • Hard drives, diskette drives and peripherals
  • Video display type and display options
  • Password protection from unauthorized use
  • Power Management feature

(CMOS) complementary metal oxide semiconductor is an on-board semiconductor chip powered by a CMOS battery inside IBM compatible computers that stores information such as the system time and system settings for your computer.

Firmware is software that is embedded in a hardware device. It is often provided on flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user. Most devices attached to modern systems are special-purpose computers in their own right, running their own software. Some of these devices store that software ("firmware") in a ROM within the device itself. Over the years, however, manufacturers have found that loading the firmware from the host system is both cheaper and more flexible. As a result, much current hardware is unable to function in any useful way until the host computer has fed it the requisite firmware. This firmware load is handled by the device driver.

Riser card / daughterboard

Riser card is a PC expansion card that can be added to a PC to give it audio, modem or networking capabilities.

Daughter boards are expansion boards that commonly connect directly to the motherboard and give the computer an added feature such as modem, audio capability ect.. . Today, these types of boards are not found or used in desktop computers and have been replaced with PCI boards. But, many laptops still use these types of boards.