Knowing your Motherboard

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Knowing your Motherboard

Post #1 by huddy » Mon Jul 01, 2013 4:24 pm

This article features on the anatomy of a motherboard. Getting to know your motherboard is essential for anyone who needs to know where everything goes, what it does and why.

Firstly, before I divulge into any detail, it's important to remember that even though both Intel and AMD motherboards look and function fairly similar, there are differences you should be aware of:

Differences between Intel and AMD

Both Intel and AMD have two notable differences:

1. The socket type
2. The HSF attachment mechanism


Intel CPUs use the Land Grid Array (LGA) to connect the CPU to the motherboard. The pins are located on the motherboard with the holes on the CPU.
Intel motherboards generally have the 4 holes open so that the HSFs are attached directly to the motherboard. Intel’s reference HSF for example, generally uses a “push-pin” system.


AMD CPUs use Pin Grid Array (PGA) to connect to the motherboard. The pins are located on the CPU with holes on the socket. These holes are normally opened and closed using the CPU retention bracket.

Okay, now you are aware of the difference, let look at a motherboard in detail.

In this article, I have illustrated an Intel LGA1156 Gigabyte GA-H55M-UD2H Intel H55.


Supplementary CPU Power Connector
Used to supply additional power to Multi-Core or high performance CPUs. The connectors could be either 4 or 8 pin connector:

The ATX 4 pin power connector (also known as the ATX12V or P4 connector) is used to supply 2 +12v rails to the CPU voltage regulator modules for CPU stability.
The ATX 8 pin power connector or EPS12V connector provides four +12v rails to the CPU voltage regulator modules for CPU stability.

Make sure your PSU has the right connections. You can purchase Molex to 4/8 pin adaptors and even 4-pin to 8-pin connectors. In some cases you can connect the 4 pin ATX12V connector to an 8 pin EPS12V socket but there are no grantees the system will remain stable and not something I would personally recommend.

CPU HSF Retention Holes (4)
All motherboards provide four holes in each corner around the CPU Socket. These are used to attach a range of Heat Sink Fans (HSF) for cooling the CPU. There are various mechanisms used to clamp the HSF in place.

Intel motherboards generally have the 4 holes open so that the HSFs are attached directly to the motherboard. Intel’s reference HSF for example, generally uses a “push and lock” system.

AMD motherboards however, normally already have a bracket preinstalled which is used for a single lever retention clip but his bracket can be removed.
Regardless of which platform you are using you can always install third party coolers but make sure they compatible with the Socket type i.e. AM2+ or LGA1156 etc. Some HSFs supply the different attachment so they can fit a wide range of Sockets.

Be careful though, some of the high end product may require a fixing plate behind the motherboard. If you are lucky that your case comes with a hole in the motherboard you may be lucky otherwise you may have to remove the motherboard if you are upgrading. This can be right pain.

CPU Socket
The CPU socket is where the CPU is inserted in to the motherboard. The sockets are designed for specific type of CPU with different packages and the arrangement of the connections pins.

The pins on the PGA (Pin Grid Array) package are arranged on the CPU whereas the pins on a LGA (Land Grid Arrays) are located in the socket.
Regardless of the package used, both are designed to ensure correct insertion by a series of notches on the CPU and the socket so they can only be installed one way with no effort or Zero Insertion Force (ZIF)

Our CPU uses the LGA package, so we can expect to see a series of pins inside the socket. A protect plate keeps these pins safe. Do not remove this until you are ready to install the CPU!

CPU Retention Spring or lever
The CPU retention lever is designed to lock the CPU firmly in place once installed.

Phase LEDs
Not all motherboards have phase LEDS but useful on new build to indicate the level of CPU loading. The higher the loading the more LEDs are lit.

RAM Slots
Your memory modules are connected to the motherboard using the RAM slots. Each type of motherboard is dependent on a particular type of memory. Such as DDR2 or DDR3. Depending on the type of motherboard you are using so it’s important that you install the correct memory type.

Each type of RAM and it’s slot has its own distinctive notch key to prevent the wrong type of memory being installed and the wrong way round. In a nutshell, if it fits then you are using the correct type of memory.

If your system supports dual-channel or triple-channel memory, then you must make sure the RAM is installed into matching banks.
The banks are spread over two or three channels to provide the system with a greater bandwidth, so it’s a worthwhile feature to use.
If you have a dual-channel memory capable motherboard, then you will need to install equal RAM modules in multiples of two in to the same memory bank normally indicated by the same colour scheme. i.e. blue or white. These are normally slots 1 and 3 or slots 2 and 4.

If you have a triple-channel memory capable motherboard like the X58 chipset, then you will need to install equal RAM modules in multiples of three in to the same memory bank. Again, like dual-channel memory, these are indicated by the same colour scheme. i.e. blue or white. These are normally slots 1, 3 and 6 or slots 2, 4 and 6 if there are six slots.

If the memory is installed into the wrong banks, don’t worry, the system will still boot and work but in a single memory channel configuration and there may be a slight hit on performance. The System normally indicates if dual or triple memory channel is enabled during the POST sequence during the boot process.
Always check the motherboard manual for memory requirements.

Floppy Disk Drive Connector
The Floppy Disk Drive (FDD) connector, as its name suggests, is used to connect a 3.5” FDD to the FDD interface on the motherboard via a 34-pin twisted ribbon cable.

Rarely used nowadays but some motherboards still support them. Although very unlikely, there may be some cases where it's still required such as driver installation when setting up RAID for example. Newer BIOS programs however tend to support USB memory sticks so the connector and the FDD are all but defunct.

IDE Connector
The IDE connector is used to connect a legacy 5.25” Hard Disk and Optical drive to the motherboard via a 40-pin IDE/ATA ribbon cable. Each IDE connector allows two devices to work on the same channel in a Master/Slave combination and the devices must be configured as such which often lead to complications. Some older motherboards provided two IDE channels (Primary and Secondary) each of which could two devices, so effectively older system could have up to four IDE devices installed at once. The speed of IDE devices depended largely on the controller, the device connected and their configuration of transfer mode. These ranged from 3.3MBs of the original PIO device through to 133MB/s of the Ultra DMA 6 ATA/133.

Since the introduction of the faster SATA interface, which also allows easier set-up and multiple devices, the IDE/ATA drives became less freely available. However, some motherboards still support the legacy drive for some backward compatibility by providing a single channel which allows up to two devices to be connected.

ATX Power Connector
The ATX power connector is used to supply the motherboard with its main power source. It supplies 3 main outputs to the motherboard: +3.3c, +5v and 12 v.
There are many variants of the ATX (Advanced Technology Extended) standards over the years but your motherboard will come with either a 20 or 24 pin connector. Most modern motherboards and PSUs support the latest 24pin (ATX2.2) standard which supply additional 12v rails to supports PCI-e.
Make sure your PSU is able to compatible with your motherboard and has the right connectors.

Motherboard Standoff Holes
The motherboard standoff holes are used to attach standoff screws which raise the motherboard above the motherboard case tray so as not to short it. Each screw holes confirms to ATX standards.

Clear CMOS Jumper
The clear CMOS jumper is used to clear the settings specified in the BIOS. The jumper is effectively a switch which clears the values held in the CMOS i.e the BIOS configurations and effectively puts the CMOS back to factory settings. Clearing the CMOS is normally done by removing the jumper cap and shorting the two exposed pins for a few seconds using a screwdriver. The jumper is designed so it can’t be accidently tripped however some enthusiast motherboards may have an actually switch somewhere instead of a jumper making it easier for the user.

If you have bought a second hand motherboard or even selling one on, it may be wise to reset the motherboard back to factory settings.

Internal SATA Ports
The Serial Advanced Technology Attachment (SATA) ports are used to attach SATA devices such as Hard Disk Drives, Solid State Drives and Optical storage devices and effectively replaces EIDE attachment. SATA currently provides data transfer of 1.5Gb/s (SATA1) 3b/s (SATA2) and more recently 6Gb/s (SATA).

Front Panel Header
The front Panel header is used for all your case front panel switches, buttons, connectors and so on. The header provides a series of pins which connect to the coloured cables that come with your case. The header usually comprises of the following:
Power Switch, Power LED, Reset Switch, Internal Speaker, Chassis Intrusion Alarm or Sensor, System Status Indicator and HDD activity.

Check your motherboard manual for correct connections

Internal USB Heads
The USB head provides a direct connection to any USB ports on the case. See USB ports in the I/O for further description.

IEE1394 “Firewire” Head
The IEEE1394 “Firewire” head provides a direct connection to any “Firewire” ports on the case. See “IEEE1394 “Firewire” ports in the I/O for further description.

COM Serial Head
Another legacy port. The COM Serial header provides the ability for attaching a serial port cable which provides an RS-232 serial port.

CPU and Chassis Fan Headers
The CPU and chassis fan headers are used to provide power to the CPU HSF and Chassis fan from the motherboard. Each header provides the required +12v needed to operate the fan. This is normally a 4-pin header where the motherboard supports fan speed control.

CD In Head
A 4-pin connector that allows an ATAPI CD-ROM to be connected directly to the motherboards audio system using an analogue audio cable. Since most motherboards now provide fast digital audio sound these connector is no longer used.

PCI-E Expansion Slot
This slot is used to connect PCIe compatible expansion cards, such as video cards, to the motherboard.

Peripheral Component Interconnect Express known as PCIe or PCI-E (same thing) replaces the old PCI and AGP standard for expansion slot interfaces. This technology uses point-to-point serial links to communicate with the motherboard rather than shared parallel link thus providing a significant increase in data traffic (bandwidth) over lanes.

These lanes transport data in 8 bit byte formats in both directions and a PCIe slot may contain one to 32 lanes in powers of two; 1, 2 4 8 16 and 32. Typically, graphics cards today will use 8/16 lanes for data transfer.

To confuse things a bit more, there are different version of PCI-e which characterises their signalling mode and bandwidth. However, all are backward compatible with previous version.

V1x. = 250 MB/s per lane or 4GB/s for a 16 land slot
V2.0 = 500 MB/s per lane or 8 GB/s for a 16 lane slot
V3.0 = 1 GB/s per lane or 16 GB/s for a 16 lane slot

Be warned by the physical appearance of the PCIe slots which can be deceptive. Do not assume that all slots provide the same number of lanes. Although they may look identical, the second or even the third slot may have less lanes than the primary slot (normally nearest the CPU).In some cases these secondary slots may be less than the required 8 lanes required for a video card. The PCI-E slots on the motherboard shown in my diagram have 16 and 4 lanes for the primary and secondary slots respectively, so you can see my point. Check your motherboard manually to ensure you insert your card in to the correct PCIe slot or when adding a second card otherwise it may not work.

PCI-E x1 Expansion Slot (Not shown on image)
The PCI-E x1 slot is a smaller version of the full PCI-E slot. It provides a single lane for smaller expansion cards such as sounds cards, Networks cards and so on.
PCI Slots

PCI (Peripheral Component Interconnect) slots are used to connect a range of legacy PCI cards such as sound cards, Network Cards, Modems and even once Graphics cards to the PCI bus on the motherboard.

Most of these are now found on the integrated circuitry of the motherboard and the graphics cards have since moved to AGP and now PCIe. However, despite the newer PCIe technology, many devices still use the PCI technology and many motherboards still provide the standard PCI slot for compatibility.

Front Audio Header
Used to connect the case audio jacks to either the motherboard via either the Intel HD or AC'97 sound header.

CMOS battery
The CMOS battery provides ongoing power to the CMOS memory state. Without it, the system will not boot. The batteries used are a standard CR2032 type. Although not essential to the build process, its important you know it’s function and where it is. If your system starts with a “Checksum error” the chances are the battery is dead and needs replacing. Although this is very unlikely, I have had the odd motherboard delivered where this has happened.


USB Ports
Universal Serial Bus, Type “A” connectors are commonly found on most motherboards to allow short distance connection of a wide range of peripherals and electronic devices to the PC such as USB memory sticks, cameras, mobile phones, printers, scanners etc. In some cases the USB interface also carry power to the device to eliminate the need for an external power source but this depends on the device itself.
Most motherboard ship with USB 2 as standard but newer boards may come with the new faster USB 3 interface. All are backward compatible.

USB 1 Provides a data rate of 12 Mbit/s for a maximum of 3 meters
USB 2 provides a data rate of 480 Mbit/s for a maximum of 5 meters
USB 3 provides a data rate of 4800 Mbit/s
(VGA) D-SUB Port

The D-Sub or D-submininture connector is used for transferring analogue signals to a range of external devices. The D comes from the shape of the metal shield that provides the orientation of the connector and the number afterwards denotes the number of pins.

The VGA (Video Graphics Array) uses a 15 pin version known as the DA15, HD15 (High Density) and DB15 which has three rows of pins capable of displaying low to mid-range resolutions. Although these have been superseded, they’re still pretty common with CRTs or budget TFTs.

High-Definition Media Interface transmits uncompressed HDCP (High- Bandwidth Digital Content Protection) compliant digital video and audio data to a compatible display.

The current version of HDMI (version 1.4) transmits data at 10.2G/bps through 8 channels and supports resolutions of up to 4096x2160 at 24 Hz. Older 1.3 versions supported 2560x1600px at 75 Hz and the original 1.0 and 1.2a supported 1920x1200px at 60 Hz.

Although this interface has been around for a while now, it’s only been recently that that have been appearing on monitors and video cards. The reason for this is its most likely that PCs have separate audio interfaces and therefore don’t actually require the extra data throughput. Unless you are connecting your PC to a HD 42’ TV, then stick to a DVI connection.

Optical S/PDIF Out Connector
The Optical S/PDIF Out connector allow you to connect to an external audio system that supports optical audio. It carries compressed digital signal via optical fibre using a TOSLINK fibre optic cable. It’s often used for connecting Dolby Digital and DTS surround sound systems.

RJ-45 LAN Port
The LAN port is used to connect a PC to a Local Area Network, Local being a small physical area like home our office. The LAN is often connected to a gateway (normally a Router or Access Point) to access a WAN (Wide Area Network) such as the Internet.

The cable used to connect to the port depends on the Topology being used but typically this will be 100BASE-TX which uses an unshielded Cat5e twisted pair copper cable or 1000BASE-T for Gigabit Ethernet. These ofer 100Mbit/s and 1000Mbit/s speeds respectively. 10, 40 and 100Gigabit is available but uncommon in desktop PCs.

Regardless of which, they all use the RJ-45 connector.

LAN Link Light 1
Connection Sped LED Orange = 1Gbps, green 100, off 10mbps

LAN Link Light 2
Activity LED – blinking = activity off no activity

Audio Jacks
The common audio jack provides analogue audio signals between audio devices using the 3.5mm TRS (Tip, Ring and Sleeve) connector. Primarily, these are used for connecting speaker systems, Microphones, headphones etc.

Each audio jack is colour coded as standard to denoted its purpose:

Orange = Dual Output, Centre Speakers, Subwoofer
Grey = Stereo Output, Side Channel Speakers
Blue = Stereo Input, Line in
Black = Stereo Output, Rear Channel Speakers
Green = Stereo Output, headphones, front channels speakers, 2.1-Channel speaker set-up.
Pink = Mono, or stereo Microphone input

As with SATA eSATA provides an external connection of connecting fast mass storage devices

IEEE 1394a (Firewire) Port
“FireWire” is a propriety of Apple Inc. and is used for high speed data isochronous data transfer between digital audio and video devices. It uses a serial bus interface standard capable of a transfer rate of 400MB/s. The use of high speed USB has pretty much made “Firewire” a defunct technology.

Display Port
DisplayPort is similar to HDMI in that it carries both video and sound digitally to a compatible TFT but it differs in many ways. DisplayPort provides faster throughput for multiple displays and high resolutions all from one connection. It uses up to four lanes to transmit data simultaneously. Ideal say for connect 4 x 1080p displays. It transmits at an effective rate of 1.296, 2.16 and 4.32Gbp/s per lane operating at 5.184, 8.64, or 17.28 Gbit/s for a 4-lane link. Resolutions of 3840×2160 @ 60 Hz is quite possible which far exceeds that of HDMI. DisplayPort is a VESA standard digital interface which carries both clock and optional sound signals. It uses 8 audio channels at a sample rate of 24bit at 192kHz. It supports 128-bit AES DisplayPort Content Protection (DPCP) as well as 40-bit High bandwidth Content Protection (HDCP). A versatile connector it remains propriety free meaning reduced cost for graphics card manufactures. Certainly one to keep an eye on but don’t threat over it. The presence of HDMI is too high at the moment.

DVI Port
DVI (Digital Video Interface) carries digital and/or analogue signals to a display device depending on the pin orientation.
In digital mode, the interface transmits uncompressed high quality digital signals to an LCD display in native format. Since digital signals avoid the degradation caused by electrical noise, DVI in digital mode produces a far superior image quality of that of analogue.

In analogue mode, DVI will transmit analogue signals only. However, additional pin orientation will allow two sets of the same data can be sent in digital and an analogue form (DVI-I). This allows easy adaption when connecting VGA monitors to DVI, hence DVI –VGA connectors can be used in most cases.
There are four types of DVI connectors that although look the same, they have different pin combinations:

DVI-D Supports uncompressed digital video signals only. These digital signals avoid the degradation of due to electrical noise and therefore produce a far superior image quality of that of analogue (single and dual link)

DVI-I Supports both digital and analogue signals (single and dual link)

DVI-A Supports analogue signals only

DVI M1-DA Supports both digital and analogue signal in dual link with additional USB support

The terms single and dual link determine the amount of data that gets pushed through. A single link has a bandwidth of 3.96Gbit/s and supports resolutions of up to 1915px x 1436px on a 4:3 ratio at 60Hz. A dual link interface, with the additional six pins, will provide a maximum bandwidth of 7.92Gbits/s for resolutions up to 3,840 × 2,400 @ 33 Hz.

PS/2 Keyboard/Mouse Port
First introduce in 1987, the PS/2 connector has long been associated for connecting keyboards and mice to PCs. Although they look similar, they are not normally interchangeable and are identified by a colour coded schemes: Purple for keyboards and green for mice.

Most modern motherboards are dropping the ports in favour of USB devices and to make room for newer ports. However, some motherboards may still supply a keyboard PS/2 port or a combined legacy PS/2 port. A legacy PS/2 port will allow either a mouse or keyboard to be connected. These are normally green and purple to indicate that the port will support either device, as with our reference motherboard.

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Re: Knowing your Motherboard

Post #2 by Oldphart » Wed May 07, 2014 10:51 pm

Its amazing huddy how many don't read their mobo manual it helps when building and solving some of the basic faults.

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Re: Knowing your Motherboard

Post #3 by SuffolkBoy » Thu May 08, 2014 10:14 am

To be fair its the most important aspect of your rig as everything is built upon it! And didnt realise Usb3 could utilise that much bandwith :o
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Re: Knowing your Motherboard

Post #4 by Frenzic » Thu May 08, 2014 12:15 pm

Some good info, thanks Huddy :)
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Re: Knowing your Motherboard

Post #5 by Gregster » Thu May 08, 2014 3:44 pm

Sweet guide and some things there that I didn't know :D
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Re: Knowing your Motherboard

Post #6 by OverFienD » Thu May 08, 2014 7:47 pm

Good bit of info Mr Hudson.
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