Im 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-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.
Integrated Motherboards
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 stable and although problems can occur, they tend to be fairly rare.
All in all, the integrated motherboard tends to be a good thing as opposed to the 'Embedded Motherboard'.
Motherboards (continued...)
Embedded Motherboards
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, what happens 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.
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 like full 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.
Motherboards (continued...)
Form Factors
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/baby AT
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 some motherboard manufacturers were worried about lawsuits. It wasn't uncommon to buy a 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 more integrated. 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 companies have 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.
