The Motherboard Notes

8/2/2019 The Motherboard Notes

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The Motherboard

The motherboard is the large circuit board inside your computer's case. It's sometimes

called the system board, the logic board, the baseboard, or less commonly, the planar

board. Everything connected to your computer system, plugs either directly or

indirectly into the motherboard.

I'm sure everyone has heard the CPU, or Central Processing Unit, referred to as the

'brain' of your computer. Well, the CPU sits on the motherboard, and if it can be called

the brain of your computer then the motherboard is truly the central nervous system.

The motherboard contains the CPU, the BIOS ROM chip (Basic Input/Output System),

and the CMOS Setup information. It has expansion slots for installing different adapter

cards like your video card, sound card, Network Interface Card, and modem. This

circuit board provides a connector for the keyboard as well as housing the keyboard

controller chip. It has RAM slots for your system's Random Access Memory (SIMMs

or DIMMs), and provides the system's chipset, controllers, and underlying circuitry

(bus system) to tie everything together.

The motherboard, more or less, is your computer. It defines your computer type,

upgradeability, and expansion capability.

Non-IntegratedMotherboards

Non-Integrated Motherboards have assemblies such as the I/O Port connectors (serial

and parallel ports), hard drive connectors or paddle boards, floppy controllers and

connectors, joystick connections, etc. installed as expansion boards. This takes up one

or more of the motherboard's expansion slots and reduces the amount of free space

inside your computer's case. Hence, the individual motherboard is relatively cheap to

produce but, because of the cost of manufacturing, testing, and installing the expansion

boards separately, there's an added cost to the computer system. However, if something

should go wrong with the individual assemblies, such as a bent or broken pin in a

connector, or a defective controller chip etc., you could repair the problem by replacing

the individual expansion card at a relatively minor cost.

Most of the older motherboards were Non-Integrated. Some of the later 486 system

boards began to integrate some of these assemblies right onto the circuit board.

IntegratedMotherboards

Integrated Motherboards have assemblies that are otherwise installed as expansion

boards, integrated or built right onto the board. The serial and parallel ports, the IDE

and floppy drive, and joystick all connect directly to the motherboard. This is now

standard on any late model 486 and above. It tends to free up some space inside the

case and allows for better accessibility and air flow. The systems are cheaper to produce

because there's less material involved, less installation, and testing can all be done at the

same time. They are more expensive to repair because, if you end up with a controller

failure or broken pin, it means a new motherboard (and, of course, because of the added

assemblies, the motherboard can be more expensive than its non-integrated

counterpart). However, these particular integrated assemblies are generally fairly stableand although problems can occur, they tend to be fairly rare.


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All in all, the integrated motherboard tends to be a good thing as opposed to the

'Embedded Motherboard'.

EmbeddedMotherboards

Cost and affordability is a concern for any manufacturer. Make your product more

affordable, and more people will buy it, creating a larger market and increased sales.This is actually the whole idea behind integrated motherboards, and that's all an

embedded motherboard is, an integrated board.

The reason I differentiate between the two is a matter of expansion, upgradeability and

configuration. In an effort to reduce the cost (and size) of a computer system even

more, manufacturers began integrating (or embedding) technologies such as video,

sound, networking and modems right onto the system board. This dramatically

increases the cost of the mainboard, but reduces the cost of the overall system for the

reasons we've discussed earlier. Also, you're pretty well stuck with what you've got.

What if you decide you would like to upgrade your sound or video technology, whathappens if your modem quits working or your sound card gives out you need a new

(expensive) motherboard. But wait, the manufacturer says that you can upgrade or

bypass a particular feature by installing an adapter card and disabling the embedded

device (sometimes). Well, this is where a few problems tend to crop up.

First off, how do you disable the device? Some are disabled as soon as you install

another device (such as a video card in an AGP slot). Others have to be disabled

through software setup programs, or in your system's CMOS setup, or by setting

jumpers on the motherboard itself, or both (and remember, some can't be upgraded,

bypassed or disabled at all).

Secondly, can I upgrade to the device I want, or am I limited? Is there a list of the

compatible devices that I can upgrade to? A lot of embedded system boards can be very

picky about the model and manufacturer of the device you're using to replace an

embedded feature.

Third, is there room for the upgrade or replacement? Remember, the manufacturer has

embedded a device to save money and reduce cost. Was more money saved by reducing

the number of expansion slots on the motherboard?

Finally, the motherboard itself is more expensive because of the embedded device.Would I not be defeating the cost saving feature by disabling the device and installing

another?

One other thing, deception. A manufacturer might say their embedded video technology

has 4 megabytes of video RAM, upgradeable to, say 12MB. What this generally means

is that you have 4MB of Video RAM (which is faster than regular system RAM), and

when you upgrade that to 12 MB, it will use 8MB of your system's RAM. ...Hmm, now

your newer video technology is using regular system RAM instead of faster VRAM,

and your 64 MB computer now has only 56 MB of memory, because 8MB has been

allocated to video. Most manufacturers don't explain that one too well.


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You may find that you do a lot of desktop publishing or enjoy gaming, and decide you'd

like to upgrade your video card to enhance your graphics and increase performance.

With an embedded system you may be limited to what you can do.

Don't get me wrong, embedded systems definitely have a niche in today's marketplace.

Laptop and Notebook computers are becoming smaller and lighter, and yet more likefull featured desktops. A few tradeoffs are not only tolerated, but expected. You may

have need of a basic business computer that does nothing but crunch numbers or access

a database and attaches to a small network. Maybe you're looking for an inexpensive

computer just for accessing the Internet or playing the odd game of solitaire. Perhaps

you play the odd action game and want to play your music CDs while you work. Maybe

you're a first time buyer and want all these features! Embedded motherboards allow for

fast, powerful, feature rich computer systems at a very reasonable cost. It's just

important to know exactly what you're getting, and the different limitations and

problems that can come up later if you decide you would like to enhance some of these

features.

From the sounds of all this, you may get the impression that I'm not particularily crazy

about embedded motherboards.

FormFactors

Form factors define the size, shape, and screw placement on a motherboard. It's usually

the technological advancements that have been achieved that allow for these changes so

I suppose the form factors also define the technology to some extent.

It's important to understand that none of these standards have to be adhered to (other

than maybe spacing between expansion slots). So, if a certain manufacturer decides to

build a system board with different screw placement or different dimensions than the

standard, it's perfectly acceptable. This board then becomes proprietary and can only be

replaced by ordering through the original company. However, if your motherboard

adheres to one of the form factors, and you decide to upgrade your motherboard at a

future date, or have to replace it for any reason, then all you have to do is buy another

motherboard that follows that standard.

PC/XT

When IBM came out with its first Personal Computer (PC), there were no standards and

the motherboard tended to be a little on the large size with more space than it really

needed. Within a short time, they had developed their Extended Technologies computer(XT), reducing the size of the motherboard to make it more compact and still accept the

different circuits and components needed for the system. The XT quickly became a

standard for motherboards in many of the clones that were being developed at the time.

AT/babyAT

Computers quickly became more and more powerful with more system memory

installed on the board, faster CPUs, and features that required more circuitry and

components. IBM had to increase the size of their boards to accept all these components

and developed the AT motherboard. At 13.5" X 12", this form factor soon became

another standard followed by other manufacturers. Size, screw placement, expansion

slot positioning, and even component placement was followed so closely that somemotherboard manufacturers were worried about lawsuits. It wasn't uncommon to buy a


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computer from an established system manufacturer, with full documentation, but no

contact information in the motherboard manual, perhaps in fear of copyright

infringement.

The AT, however, pretty well became industry standard throughout the 80's and into the

early 90's. As technology advanced, circuits and components became smaller and moreintegrated. Many companies decided to reduce the size of the motherboard again.

Because the AT had been standard for so many years they retained the placement of the

expansion slots and the screw positioning on a 13" X 8.5 or 9" board. This meant that

an AT board could be replaced with a 'baby AT' or 'mini AT' board and still fit in the

same case.

The baby AT form factor all but completely replaced the AT and is still available, but

has never been made a true standard.

ATX

Because the baby AT form factor was never made a true standard, many companieshave taken liberties with different dimensions and design. The ATX is a form factor

developed by Intel that closely conforms to the baby AT size. It puts together some of

the better ideas, engineering and design to make a standard that is cheaper to develop,

allows for better component access, and in some ways is faster and more stable.

The ATX board measures approximately 9.5" X 12" and takes the baby AT board and

turns it 90 degrees to put the long edge of the board along the back of the computer

case, which provides maximum space for expansion slots and I/O ports.

The different I/O ports, USB connector and the PS/2 keyboard and mouse connectors

are stacked or 'layered' and hardwired directly to the motherboard. The absence of a

cable connector reduces radio interference as well as production costs. The ATX

motherboard also defines the number and placement of mounting holes and uses a

different power connection and a different (PS/2) power supply.

The ATX standard also provides for a smaller 'mini ATX' form factor which cuts the

size of a board down to 8.2" X 11.2" and removes one row of mounting holes. These

boards will fit in a regular ATX style case.

Inside the computer case

Some people get a little excited when they look inside a computer and see all the

different electrical components and circuit boards. All the wires, connectors and data

cables inside tend to be a little intimidating. Yet, all of today's computer repairs,

replacements, upgrades and installations are getting easier and easier.

A technician could spend hours (at outrageous prices) to search for a specific chip or

failed solder connection that's causing a particular problem. Repairs aren't done at the

chip level anymore. Everything is very modular. It's quicker, easier, and much more

economical to have the technician pop in a whole new video card or motherboard.


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It's still important to know some of the different components and what they do. It can

give you an insight as to which particular module may need replacement, and aids in

the troubleshooting process.

It may only take 5 minutes to replace a particularFRU (Field Replaceable Unit), but it

might require a lot more time to troubleshoot the problem and discover which moduleneeds replacement.

Even if you don't plan on becoming A+ (A Plus) Certified, if you've come this far you

must have an interest in computers. This is a great place to learn about what's inside that

case.

Start this section with ESD (Electrostatic Discharge) precautions and work your way

through in order. Once you understand ESD and the precautions you should take, go

ahead and open the case. See if you can find the different components, connectors, and

devices discussed. When you do, try and discover everything you can about it. What

kind of chip is it? What does it do? What kind of socket does it fit into? How much datacan it move at once? How fast is it?

If you have room on your desk, you can run your computer with the cover off * so you

can look inside as you read (keep your hands out).

*Note: Only run your system with the cover off for a short period of time. Contrary to

popular belief, leaving the cover off can interrupt the airflow, actually contributing to

overheating in some cases. For short periods of time it should be OK. In fact, its often

necessary when troubleshooting hardware. Its also a good time to make sure the CPU

fan is working properly!

By the time you're done, you'll be removing and reinstalling some of the devices inside.

Look around for an old 286 or 386 computer. They can be picked up for less than 50

dollars, in working condition. Whether it's working, or not, you can learn an awful lot

by taking it apart and putting it back together.

Please Remember: Do Not take apart a monitor or power supply, there is enough stored

electricity inside to cause you serious injury!

Good luck, and always remember your ESD precautions!
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The Motherboard Notes