The Motherboard

What is motherboard?
It is the main circuit board within a typical desktop computer, laptop or server. Its main functions are as follows:

• To serve as a central backbone to which all other modular parts such as CPU, RAM, and hard drives can be attached as required to create a computer.
• To accept (on many motherboards) different components (in particular CPU and expansion cards) for the purposes of customization.
• To distribute power to PC components.
• To electronically co-ordinate and interface the operation of the components.

Form factor is the specification of a motherboard – the dimensions, power supply type, location of mounting holes, number of ports on the back panel, etc.

Figure 1.1 Motherboard measurement in millimeters

HOW TO INSTALL MOTHERBOARD?

SAFETY PRECAUTIONS

•      Follow these safety precautions when installing the motherboard

•   Wear a grounding strap attached to a grounded device to avoid damage from static electricity

•      Discharge static electricity by touching the metal case of a safely grounded object before working on the motherboard

•      Leave components in the static-proof bags they came in

•      Hold all circuit boards by the edges. Do not bend circuit boards.

CHOOSING A COMPUTER CASE

•      Make   sure   that   your   case   supports   all   the   features   required. 

•      Make   sure   that   your   case   has   sufficient   power   and   space   for   all   drives   that   you   intend   to install.

•      Most cases have a choice of I/O templates in the rear panel. Make sure that the I/O template in   the   case   matches   the   I/O   ports   installed   on   the   rear   edge   of   the   motherboard.

•      Choose   a   case   that accommodates   this   form   factor.

INSTALLING THE MOTHERBOARD IN A CASE

•      Refer   to   the   following   illustration   and   instructions   for   installing   the   motherboard   in   a   case.

•      Most   system   cases   have   mounting   brackets   installed   in   the   case,   which   correspond   the   holes in   the   motherboard.   Place   the   motherboard   over   the   mounting   brackets   and   secure   the motherboard   onto   the   mounting   brackets   with   screws.

•      Ensure   that   your   case   has   an   I/O   template   that   supports   the   I/O   ports   and   expansion   slots on   your   motherboard.

CHECKING JUMPER SETTINGS

This   section   explains   how   to   set   jumpers   for   correct   configuration   of   the   motherboard.

 The illustrations show a 2-pin jumper.  When the jumper cap is placed on both pins, the jumper is SHORT.  If you remove the jumper cap, or place the jumper cap on just one pin, the jumper is OPEN.

This illustration shows a 3-pin jumper.  Pin 1 and 2 are SHORT

The following illustration shows the location of the motherboard jumpers.  Pin 1 is labeled.

CONNECTING CASE COMPONENTS

After you have installed the motherboard into a case, you can begin connecting the motherboard components.  Refer to the following:

1.   Connect the CPU cooling fan cable to CPU_FAN.

2.   Connect the case cooling fan connector to SYS_FAN.

3.   Connect the case speaker cable to SPK1.

4.   Connect the case switches and indicator LEDs to the PANEL1.

5.   Connect the standard power supply connector to ATX1.

6.   Connect the auxiliary case power supply connector to ATX12V.

Front Panel Header

The front panel header (PANEL1) provides a standard set of switch and LED headers commonly found on ATX or micro-ATX cases.  Refer to the table below for information:

Hard Drive Activity LED

Connecting pins 1 and 3 to a front panel mounted LED provides visual indication that data is being read from or written to the hard drive.  For the LED to function properly, an IDE drive should be connected to the onboard IDE interface.  The LED will also show activity for devices connected to the SCSI (hard drive activity LED) connector.

Power/Sleep/Message waiting LED

Connecting pins 2 and 4 to a single or dual-color, front panel mounted LED provides power on/off, sleep, and message waiting indication.

Reset Switch

Supporting the reset function requires connecting pin 5 and 7 to a momentary contact switch that is normally open. When the switch is closed, the board resets and runs POST.

Power Switch

Supporting the power on/off function requires connecting pins 6 and 8 to a momentary contact switch that is normally open. The switch should maintain contact for at least 50 ms to signal the power supply to switch on or off.  The time requirement is due to internal debounce circuitry. After receiving a power on/off signal, at least two seconds elapses before the power supply recognizes another on/off signal.