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Hardware Emergency Room:   Motherboard
Contents: The Motherboard
Sockets and Slots
Chip Sets
ROM BIOS
ROM BIOS Upgrade
Motherboard Upgrades
Motherboard Problems

The Motherboard
The motherboard (sometimes referred to as system or main board) in your computer is a highly complicated piece of hardware.  It is the basis of any computer, and possibly its single most important part.  The typical motherboard contains a number of individual components, including:

Motherboard
motherboard
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  • CPU socket (or slot)
  • CPU voltage regulators
  • Chip set
  • Memory SIMM or DIMM sockets
  • Level 2 cache
  • Bus slots
  • ROM BIOS
  • Level 2 cache
  • Super I/O chip
  • Clock/CMOS battery
All the critical subsystems run directly off of your system's motherboard, and it manages all the data transactions between the CPU and the computer's peripherals.
It's a good idea to identify the crucial parts of your system's motherboard.  Although each motherboard is designed differently, its actually quite easy to identify most of the major components by their size, shape and placement.  Of course, having your system's manual on hand will make this task a lot easier. Major Components
mboarddiag
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The physical dimensions (shape and size) of the motherboard dictate the type of case it can fit into.  There are several common dimension standards for motherboards.   Because non-standard boards are hard to upgrade, it is wise to avoid them.  A truly standardized motherboard is interchangeable with other boards of its type.
A few of the most common standards for motherboards are: Full-sized AT, Baby-AT, ATX and NLX.  Systems that use proprietary motherboards, such as Compaq and Packard Bell, can be very expensive or even impossible to upgrade or repair after the warranty has expired.

Sockets and Slots

When examining your motherboard, you'll likely find it designated something like  "Socket 7," "Socket 8," or "Slot 1."   These classifications refer to the type of CPU that the motherboard can support.

For example:

  • Socket 7 motherboards are generally designed for Pentium and Pentium MMX CPUs
  • Socket 8 motherboards are made for Pentium Pro CPUs.
  • Slot 1 motherboards are for Pentium II systems.
These designations mean that the motherboard supports a given class of processor, as opposed to any such processor.   Some Socket 7 motherboards can support all Pentium and Pentium MMX CPUs, but older Socket 7 motherboards might only support Pentium CPUs up to 120MHz.

Chip Sets

If the CPU is the brain of your computer, the chip set is its heart.  It controls the data that flow between your computer's CPU, system memory and the system bus.  Chip sets are intelligent controller chips that are located on the motherboard.  They are a critical component that is closely related to the CPU because they control the buses around it.  Chip sets are the mechanism that allows the RAM and the I/O buses to work with the CPU. 

Comprised of one or more chips, chip sets integrate numerous functions, including the Clock Generator, Bus Controller, System Timer, Interrupt Controller, DMA Controller, CMOS RAM Clock and Keyboard Controller.

There are many different chip sets and new, improved (faster, added capabilities) chip sets are introduced continuously.   Historically, Intel has been the leader in chip set technology, releasing successive generations with new and more powerful features, but a number of other companies (Acer Laboratories, VIA Technologies and Silicon integrated Systems to name three) manufacture chip sets as well.

CPU
pentium
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Chip Set
chipset
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ROM BIOS

The ROM BIOS chip on your motherboard contains instructions which are specific to that particular motherboard.  The ROM BIOS is like the low-level brain needed to get your computer's various parts to work together.  The BIOS is what enables different operating systems to run on almost any PC despite hardware differences.  And because it communicates directly with the hardware, a computer's BIOS must match it exactly.

ROM BIOS
ROM
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The ROM BIOS instructions include several different programs that will remain in your PC throughout its life; they are usually not changed.  These instructions are primarily used for system start-up and include:
  • The Power On Self Test (POST)
  • The Setup instructions, which connect with the CMOS instructions
  • BIOS instructions, which connect with the various hardware peripherals
  • The Boot instructions, which calls the operating system
During start-up you can see the name of your ROM chip when the BIOS is specified.   A couple of the most common suppliers are American Megatrends (AMI) and Phoenix.

BIOS Screen
amibios
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ROM BIOS Upgrade

Occasionally you may need to do a BIOS upgrade.  Most often this will happen if you need to install a new hardware device that your current BIOS does not support.  This is not a hardware upgrade but rather an update of the ROM BIOS code.  Modern motherboards store the BIOS instructions in what are called "Flash ROM", which can (despite the name) be updated. 

You can get new BIOS software from your supplier, or the Internet.  Instructions for loading the BIOS upgrade should accompany any update file, and you should follow them carefully.  Always remember to write down all your CMOS setup settings prior to the upgrade, as you will need to reset them.  It is not advisable to update your Flash ROM  without good reason, and it is always best to get the update directly from your motherboard's manufacturer rather than a third party, because a faulty update can have disastrous results.

Motherboard Upgrades

Upgrading your entire motherboard is a major endeavor not for the faint of heart.   Many experts recommend selling your system and investing the proceeds to buy a new one over upgrading the system board.  Some of your old components may not work with a new motherboard, so it can be an expensive proposition.

That being said, assuming you can find the right shape board and are willing to dedicate the time required to getting all the details right, it can be done.  Once you have found the proper size, you need to choose your new CPU, chip set and memory.  You may be able to use your old memory with the new motherboard, but odds are you can't due to technological change.

If you are buying a replacement motherboard look for these important features:

  • Fully supports Plug-and-Play (PnP).
  • Takes SDRAM 168-pin DIMMs (if you are buying new memory).
  • Has industry standard BIOS that supports PnP.
  • Includes one or more ISA bus slots.
  • Has at least three PCI revision 2.1 local bus slots.
  • Includes built-in floppy controller, built-in primary and secondary local bus (PCI, EIDE) connectors, built-in high-speed serial ports, USB ports, and high-speed parallel port.
  • Has detailed, understandable, complete documentation.

CPU
pentium
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Chip Set
chipset
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Memory Module
dimm
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One warning: swapping a new Pentium II board into an older system chassis may be hazardous to your new CPU.  The Pentium II (Slot 1) cooling requirements are substantially different than the Pentium (Socket 7).

Motherboard Problems

Because your computer's motherboard is a complex piece of electronics that handles numerous system resources, troubleshooting problems can be difficult and time consuming.  And because it is expandable -- allowing for the addition of "expansion devices" such as sound cards and the like -- resource conflicts can result when you add new devices (there are three types of resources provided by the motherboard for expansion devices: Interrupt Requests, DMA channels, and I/O port addresses). 

As expansion devices are added to a PC, resources are assigned to each particular device and no two devices may use the same resources -- if this happens, conflicts occur and the system will work improperly or not at all.   You can get more help with such resource conflict in our I/O & Expansion Cards troubleshooting section.  

 

When problems are indicated with your motherboard, it is wise to do the following general checks to make sure the problem isn't a basic one.  Always remember to unplug the system when working on it and to use proper ESD protection.
  • Check all cables and connectors.  Make sure all cables are seated securely.   Make sure all of your cables are in good working order, do not have frayed or damaged edges or ends, and are not crimped by the cover when replacing it.
  • Check all socket-mounted components such as the CPU.  Make sure they are securely seated, and that any locking levers are tightly locked down.
  • Check power levels, including the wall outlet and other devices (such as printers or coffee pots) that may be using the same circuit and causing power fluctuations.
  • Check the motherboard for foreign objects such as loose screws, loose wires, or other objects that may be short circuiting it.  Make sure there are no cracks.
  • Use your manual to confirm that all the jumpers and dip switches on the motherboard are correctly set.
 

Cables
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CPU Socket
cpusocket.jpg (17480 bytes)
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Before taking the drastic step of replacing your motherboard, go to the next level of troubleshooting steps:
  • Remove all optional devices from the motherboard, including expansion boards, external peripherals, etc. so that you leave just the minimum in the machine required to make it work (CPU, full bank of memory, video card and drive).  See if that resolves the problem.
  • Reset all CMOS BIOS settings to the default, conservative values to make sure an overly aggressive BIOS setting isn't causing the problem.  Set all cache, memory and hard disk timing to as slow as possible and turn off BIOS shadowing.
  • Try replacing the video card with a known-good one.
  • Try replacing the power supply with a newer, more powerful one.

Expansion Board
nic
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CMOS Setup
cmos
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If your computer spontaneously reboots or crashes for no apparent reason:
  • Check your system for viruses immediately.  This is a symptom of memory-resident viruses. 
  • Check your power supply cables -- both external and internal.  Make sure your internal 4-pin cables are seated securely on the motherboard.
  • Move your computer to another power outlet.
  • Make sure your CPU is seated securely and that the heat-sink/fan is operating properly to keep it cool.
  • Make sure your computer's memory modules are seated securely.
  • Check that all your expansion boards are seated securely and evenly on the motherboard.  
  • Examine your motherboard for metal pieces that might be touching other metal pieces (such as screws or the board's seatings).
  • If you recently added a new expansion board, make sure there are no interrupt (IRQ), DMA channel or I/O address conflicts.
 

Power Cable
powercable
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Memory Module
dimm
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If you can not get your system to boot up, but the problem goes away when the PC's outer cover is removed:
  • Try placing the cover on the system and booting PRIOR to replacing any of the cover's screws.
  • If the PC boots without any screws securing the cover, carefully insert and tighten each screw with the system on.
  • This way you may find the screw that is causing an intermittent connection -- leave it out for the short-run, but in the long-term, you will need to replace the motherboard.
If you are unable to get a parallel-port device (for example, a printer) to work with your motherboard:
  • Check that the CMOS Setup parallel-port mode (i.e., SPP/ECP/EPP) is configured correctly for the peripheral device you are trying to use.

CMOS Setup
cmos
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Disclaimer:  These pages are provided for information purposes only.  We cannot be held responsible for any damage you might inflict on your system while using the information contained herein.  We recommend you always refer any technical matter that is "over your head" to a qualified computer technician.
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2011 Double-Hammer Computer Services.  All rights reserved.
Last Updated: September 04, 2011

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