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Motherboard Basics


									Motherboard Basics

The motherboard is the main part of your computer that everything else plugs
into. Sometimes it is called the system board. A typical motherboard is a sheet
of olive green or brown fiberglass with many gold lines on it and chips sticking
from it.

By itself, the motherboard is just an empty plate. The stuff that sits on it does
the work. On it, we have the CPU, SIMM sockets, BIOS, and slots. On some
older boards, there is also a separate math-coprocessor. The gold lines act like
roadways of information between all of the components. These roads enable
the parts to communicate and perform the functions of your computer.

What to look for:

-There are many parts of the motherboard to consider. I'll start with the bus
speed. CPUs before the Pentium II 350 were mostly designed around a 66 MHz
bus speed. The Pentium II 350 and beyond use the 100 MHz bus speed. Newer
Pentium IIIs and Athlon CPUs use 133 MHz bus speed. Be sure you have a
motherboard that supports the CPU's bus speed that you are getting as well as
the multiplier that is needed to get the CPU's speed (a 1 GHz (1,000 MHz) cpu
may run at multilplier 10 times 100 MHz bus speed = 1,000 MHz CPU speed or
it may run at multiplier 7.5 times 133 Mhz bus speed). Bus speeds higher than
the CPU's default can be helpful for Overclocking. Along with the proper bus
speed, you also need to be sure it fully supports your CPU through voltage
requirements and CPU connection type. If you're buying a Pentium III FCPGA
CPU, it must have a Socket 370 CPU connection. If you're buying a Pentium III
SECC2 CPU, you need a Slot 1 CPU connection. Pentium IV CPUs use Socket
423 and newer ones use Socket 478. AMD's Athlon CPUs require a Socket A
CPU connection (Slot A was used with their older CPUs).

- Socketed motherboards are becoming more common than Slotted
motherboards. Because of this, I would advise getting a socketed motherboard.
However, many socketed CPUs can be used in slotted motherboards with a
slotket adapter.

-Onboard cache used to be important, but not something to worry about now
since all motherboards no longer use cache memory (instead, the cache
memory is on the CPU itself).

-The type of Chipset is also VERY important (actually, this is the most
important thing to consider in your motherboard). The chipset contains all of
the motherboard's basic instructions, and also determines many of the
motherboard's features.-

-Hardware support is also quite important as you want your motherboard to
support the hardware you are putting in it. Most of this will be determined by
the chipset, but some will not, such as number of slots for memory expansion,
number of PCI, ISA, and AGP slots-. There will always be one or zero AGP slots,
but the number of PCI and ISA slots may vary. All new motherboards have one
AGP slot. Avoid motherboards with few PCI slots or many ISA slots. ISA will
soon be eliminated completely and PCI will take over. Most newer
motherboards don't have ISA slots. Look for at least 3 DIMM slots for memory
in a newer motherboard. Also look for USB connectors as these may come in
handy for connecting peripherals. USB 2.0 is now available and may also be a
feature to look for.

-Voltage settings are also important. The motherboard must support the
voltage that your CPU runs at. In addition, if you are overclocking, a wide
variety of voltage settings may be helpful to get your CPU to run at the speed
you're aiming for.

-Onboard components are usually something to avoid. They can cause
problems when adding other components because the onboard components
take up IRQs which may be needed for other devices. Having them on the
motherboard means you may not be able to upgrade them, and it at least
means that you would be wasting money to have onboard video for example
and then buy a video card.

-Another thing to consider is whether the motherboard comes with a cooling
fan on the chipset. As speeds increase and chipsets become more complex,
having good cooling becomes more important. While this isn't one of the most
important things to consider, it is another sign of a good motherboard.

- Last, is the board AT or ATX? ATX motherboards have different power supply
connectors and different design from AT boards, in addition to being larger.
Your case MUST support the type of motherboard you are getting. Almost all
new motherboards and cases are of the ATX design. Keep in mind that many
retail computer manufacturers use their own proprietary motherboard and case
designs (i.e. Compaq and Hewlett-Packard).
How To Chose A Motherboard?

 1. Make sure your motherboard is physically and electrically compatible with your
    processor. The two main factors to consider are: the processor form factor and bus
    speed support. Desktop processors come in the following form factors: Socket 7 - for
    Pentium, Cyrix, and AMD K5/K6 series; Socket 370 - for Pentium III (Coppermine,
    Tualatin), Celeron/II; Socket A/462 - for AMD Thunderbird, Athlon, Duron, XP, MP;
    Socket 423 - for older Pentium 4 CPUs under 2.0GHz; Socket 478 - for the current
    generation of Pentium 4 processors and Celeron Processors; Slot 1 - For older Pentium
    II, Pentium III (under 1 GHz), and some Celeron processors; and Slot A - For original
    classic Athlon processors and some older Thunderbird processors (under 1GHz).

     If you are building a new system we highly recommend going with a CPU and
     motherboard that is of current technology such as, the AMD Athlon XP or the Intel
     Pentium 4 (Socket 478), in order to maintain an upgrade path. Once you know what form
     factor you are going to use you must make sure that the motherboard you are going to
     use supports the bus speed of your processor or higher. For instance, if you were buying
     an Intel Pentium 4 processor with a 533MHz bus it doesn't make sense to buy a
     motherboard that only supports a max bus speed of 400MHz. If you were to try to do so
     then the processor would either not work at all in the motherboard or at the very least it
     would not work at the right speed. Likewise, you wouldn't want to purchase an Athlon XP
     processor with a 333MHz bus and run it on a motherboard that only supports a 266MHz
     bus. For the best upgrade path go with a motherboard that supports the fastest bus
     speed of the processor form factor you want to use. (533MHz for Socket 478,
     333MHz/400MHz for Socket A, and 133MHz for Socket 370).

 2. The reliability of a motherboard as measured by return rates is roughly correlated with the
    price you pay. As a rule of thumb: the higher the price the better the reliability. We
    suspect that manufacturers who have higher profit margins do more extensive testing
    and quality control before shipping. Therefore, we suggest that you buy a motherboard of
    the highest price your budget can afford. It is not easy to replace a motherboard, even for
    professional technicians. Besides, if the motherboard is bad, your whole system is likely
    to be in jeopardy.

 3. On the other hand, motherboards do not have any moving, consumable parts. If they go
    bad, most often they do so within a month. If you can take your chances and are willing to
    learn how to replace a motherboard, the less expensive motherboards are just fine for
    budget minded buyers. To help eliminate the chance of failure we highly recommend
    using our testing service.

 4. Buy current but proven technology. Purchasing yesterday's technology can mean greater
    difficulty or limitation in future upgrades. For example, it doesn't make sense to buy a
    Socket 423 motherboard anymore since Intel stopped making Socket 423 processors
    when they reached the 2.0GHz speed. Socket 423 processors are now starting to
    become rare and their performance is lacking compared to newer Socket 478 versions.
    Similarly, it doesn't make sense to buy a motherboard that doesn't support ATA100 or
    ATA133. Most hard drives are ATA100 or ATA133 now and they can run significantly
    faster then older ATA66 or ATA33 drives.

 5. WARNING: Changing a motherboard from one type to another with different
    BIOS/chipset usually requires reinstallation of your operating system, particularly under
    Windows 9x. This happens because Windows 9x is designed to be "smart" enough to
    recognize some hardware; however, once it is set you can't change it easily. This can be
    an upgrade nightmare if you are not prepared for it. Be prepared to do a full operating
    system install/re-install when you change a motherboard!

6. Make sure your motherboard form factor (AT, ATX, micro ATX, flexATX, or Mini-ITX)
   matches that of your case. It is possible for an AT motherboard to fit inside an ATX case
   so long as the case power supply has an AT connector. It is very difficult if not impossible
   to fit an ATX motherboard in an AT case. A microATX or flexATX motherboard will fit in a
   regular ATX case. But a regular ATX motherboard will NOT fit in a microATX/flexATX
   case. By all means, buy a new case with your new motherboard if any doubt exists. They
   come with a brand-new power supply and warranty.

7. ATX is currently the industry standard form factor for motherboards and cases. MicroATX
   and FlexATX are the small and smaller "brothers" of ATX, allowing ever-smaller systems.
   MiniITX is a new smaller format primarily used and marketed by VIA. It is very small
   compared to other formats, but finding appropriate cases and power supplies may be
   difficult at this time.

8. Regarding chipsets: The chipset is what makes your motherboard work. Different
   chipsets support different things, and have different integrated features. Chipset
   companies are usually very competitive, especially third party ones such as nVIDIA, VIA
   and SiS. In general the newer a chipset is for a given series of processors, the better the
   performance will be. However, the first few motherboards with a brand new chipset are
   more likely to have problems then motherboards produced later on. Often these sorts of
   problems are cleared up through patches, bios updates, and other fixes but it can be
   disappointing to get the latest, hottest new motherboard on the market and then find out it
   doesn't like part x due to a bios problem after you install the board. The saying goes: "If
   you stay on the bleeding edge, then you are likely to bleed." The best thing to do is to
   research the motherboard you are interested in at the manufacturer's website and at
   popular review websites. It usually isn't a good sign if the motherboard manufacturer
   does not have at least one bios update available. Also, motherboard manufacturers learn
   from the mistakes of their rivals and from their own previous mistakes. The third or fourth
   motherboard that hits the market using a new chipset is less likely to have problems than
   the first one to hit the market.

9. To integrate or not to integrate? Integration is a current industry trend. It saves cost and
   space to integrate as many components onto the motherboard as possible such as video,
   audio, modem, and network card. Integrated motherboards tend to have limitations on
   future upgradeability and expandability. It is not recommended for power users. It may
   however serve first-time and budget-minded buyers and as a second machine as well.
   The reliability of integrated motherboards has improved significantly in recent years,
   although the chances for something to go wrong on an integrated motherboard is still
   higher than a non-integrated one. Integrated motherboards using nVIDIA chipsets
   currently offer the best performance in this segment.

10. Convenience factor: If you are familiar with or have a large installation base with one
    brand/model of motherboard, staying with the same brand may help you minimize the
    number of manuals to keep. If nothing else, you want to keep your motherboard manual
    for as long as possible in the event of a problem with the manufacturer. Motherboard
    manufactures now usually offer downloadable versions of their manuals online in order to
    assist their customers and to provide a way to correct errata. However, some
    manufacturers have been known to change the features on a motherboard without
    changing motherboard model. This creates problems later on if you have to download a
    manual as the motherboard you have may be different than the revised one that manual
    is meant for.
11. If volume matters to you, guess who is by far the number one motherboard manufacturer
    in sales? Intel. Their motherboards are not often seen in retail channels, partially because
    of their high prices. Their volume comes mainly from OEM channels! Asus and
    AOpen/Acer are in second and third places.
How Motherboards Work
The motherboard has been an integral part of most personal computers for more than 20
years. Think of a motherboard as a scale model of a futuristic city with many modular plug-in
buildings, each using power from a common electrical system. Multiple-lane highways of
various widths transport data between the buildings. The motherboard is the data and power
infrastructure for the entire computer.

Motherboards (also called mainboards) are actually a carryover from architecture used for
years in mainframe computers. Various circuit cards performing various functions all plug
into many similar sockets on a common circuit board. Each circuit card performs a unique
function in the computer and gets its power from the socket.

Due to improvements in circuitry and packaging, motherboards have essentially stayed the
same size or shrunk while their functionality has skyrocketed. In this edition of
HowStuffWorks, you will learn how the motherboard operates and what its many sockets
and connectors do.

The original IBM PC contained the original PC motherboard. In this design, which premiered
in 1982, the motherboard itself was a large printed circuit card that contained the 8088
microprocessor, the BIOS, sockets for the CPU's RAM and a collection of slots that auxiliary
cards could plug into. If you wanted to add a floppy disk drive or a parallel port or a joystick,
you bought a separate card and plugged it into one of the slots. This approach was
pioneered in the mass market by the Apple II machine. By making it easy to add cards,
Apple and IBM accomplished two huge things:

 They made it easy to add new features to the machine over time.
 They opened the computer to creative opportunities for third-party vendors.

Different motherboards of different vintages typically have different form factors. The form
factor is essentially the size, shape and design of the actual motherboard. There are more
than a half-dozen form factors for motherboards -- check out PC Guide's Motherboard Form
Factors to find out about the various designations.

The motherboard, by enabling pluggable components, allows users to personalize a
computer system depending on their applications and needs.

On the Motherboard
A motherboard is a multi-layered printed circuit board. Copper circuit paths called traces
that resemble a complicated roadmap carry signals and voltages across the motherboard.
Layered fabrication techniques are used so that some layers of a board can carry data for
the BIOS, processor and memory buses while other layers carry voltage and ground returns
without the paths short-circuiting at intersections. The insulated layers are manufactured into
one complete, complex sandwich. Chips and sockets are soldered onto the motherboard.

The MSI 694D Pro AR supports dual Pentium microprocessors, has five PCI slots and a
communications network riser (CNR) slot. The board supports 133 MHz bus speeds and
ultra-direct memory access-100 (UDMA). There are four USB ports and onboard audio in the
ATX form factor board.

                 MSI 694D Pro AR Dual Flip Chip Socket 370 motherboard

The Abit KT-7A supports Advanced Micro Devices (AMD) processors and has the KT-133A
chipset. The card slots on the Abit KT-7A, from bottom to top in the image below, shows that
ISA has one slot, PCI has six slots and AGP has one slot. A special fan cools the chipset.
                        Abit KT-7A AMD Processor Motherboard

A partial view of the TechRam S3ProM motherboard shows slots: From bottom to top, ISA
has one slot, PCI has two slots, audio modem riser (AMR) has one slot, and AGP has one
                             TechRam S3ProM Motherboard

The BIOS chip is common to many motherboards.

                                        BIOS Chip

Data Bus Width
Modern Pentium class motherboards have a data bus with 64 bits. That is the width of the
data highway that goes in and out of the processor. The Pentium processors, however, do
use 32-bit registers to handle 32-bit instructions.

Bus speeds and widths have increased due to faster processors and the needs of
multimedia applications. Typical bus names and widths are:
      Industry Standard Architecture (ISA) - 8 or 16 bits
      Extended Industry Standard Architecture (EISA) - 8 or16 bits
      Microchannel Architecture (MCA) - 16 or 32 bits
      VESA Local Bus (VLB) - 32 bits
      Peripheral Component Interconnect (PCI) - 32 or 64 bits
      Accelerated Graphics Port (AGP ) - 32 bits

Chipsets provide the support for the processor chip on the motherboard. The Intel 440BX is
the dominant chipset in the non-Apple personal computers. The chipset is the heart of the
computer since it controls and determines how fast and which type of processor, memory,
and slots are used. Another chip on the motherboard is called the Super I/O controller. Its
main function is to control the floppy disk drive, keyboard, mouse, serial and printer ports.
Check out PCGuide's Super I/O Controller Functions to learn more.

Recent motherboard designs include additional chips to support USB, sound card, video
adapter, computer host and network adapter. These chips save the cost of an adapter slot.

Speeds, temperatures, density, faster chipset designs and component count have driven the
need for circuit cooling via miniature electric fans. These fans mount inside the actual
computer case. Heat sinks act like a car radiator, providing additional surface area to help
cool a component.

Replaceable fan/heat-sink assemblies are often used to help dissipate the considerable
amount of heat on modern processor chips. The assembly conducts heat away from the chip
by convection, using a layer of thermal grease between the two mating metal surfaces. Fans
often have a third wire used for monitoring the speed of the fan.
 Mother board report

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