Basic Components of Computer Motherboard Explained

The motherboard, sometimes referred to as system board, is the central part of a computer that brings together all devices attached to the computer. The main components on the motherboard are the CPU (Central Processing Unit) and CPU chipset, expansion bus, I/O (Input/Output) interface, disk drive controllers, and Random Access Memory (RAM). The motherboard's main function is to distribute power and data to all devices attached to it.

What exactly is Motherboard Form Factor?

Motherboards have different form factors. A form factor is simply the physical size and layout of the motherboard and its components. Several form factors and their features are described below.

Advanced Technology (AT) and Baby AT

Advanced Technology (AT) and baby AT form factors were the most popular types of motherboards on the market. The main difference between the two is the width of the motherboards, themselves. The AT motherboard is 12 inches wide by 13 inches long. The baby AT is 9 inches wide by 10 inches long. See Figure 2.1 for the baby AT and its components.

The AT and baby AT form factors have the processor and memory socket locations toward the front of the motherboard. Very long expansion cards were designed to extend over them, which made removing the processor difficult. One had to take the expansion cards out first to remove the processor or to get to the memory. It is important to note that an AT power supply gives an output of 12V and 5V to the motherboard. Additional regulators are needed on the motherboard if 3.3V cards (peripheral component interface, or PCI) or processors are used.

This design was acceptable when clearance and cooling were not issues. With the advent of faster Pentium-class processors, which required more cooling and memory sockets that extended off the motherboards, a better motherboard design was needed.

LPX

Western Digital introduced the Low Profile Extensions (LPX) motherboard form factor. This form factor was developed to meet the need for a slimmer desktop. This goal was accomplished based on the implementation of a riser card that extended from the motherboard and allowed expansion cards to be installed parallel to the motherboard.

NLX

As the need for more expansion slots and easier access to components increased, the LPX form factor was redesigned by Intel and named the NLX (InteLex) form factor. The NLX form factor moved the riser card from the center of the motherboard to the outside edge.

ATX

The ATX form factor was developed to solve the problems associated with the baby AT form factor design. This new design had many advantages that affected not only the motherboard, but the system unit and power supply, as well. The dimensions of the ATX form factor are 12 inches wide by 9.6 inches long. A mini ATX is typically 11.2 inches wide by 8.2 inches long.

Below are the advantages of ATX form factor.

1. Integrated I/O port connection.

Baby AT motherboards have cables connecting them to the physical serial and parallel ports mounted on the system unit. With the ATX form factor, this connection is integrated into the motherboard. The ATX form factor uses a 20-pin plastic power supply connector. This is called a keyed connector, and it can be plugged into the motherboard in one direction only.

2. Integrated PS/2 mouse connector.

ATX motherboards have PS/2 mouse ports integrated into the motherboard. Most baby AT motherboards do not have a PS/2 mouse port. Older-style AT motherboards required a serial mouse.

3. Easier access to components.

The ATX motherboard was designed with functionality and accessibility in mind. It provides much easier access to components than the baby AT form factor and offers more room in general for additional components.

4. Improved power supply connection.

The new ATX form factor incorporated a single 20-pin connector in place of the pair of 6-pin connectors used on the baby AT motherboard.

5. Support for 3.3V.

The ATX motherboard supports 3.3V power from the ATX power supply. This voltage is used by most new processors.

6. 'Soft switch' power support.

The ATX power supply uses a signal from the motherboard to turn itself off. This feature enables you to use the power management utilities offered with newer operating systems to shut down a computer, as opposed to physically turning it off with the power button.

7. Better airflow.

With the ATX form factor, the processor is moved closer to the power supply, providing it with better air circulation and cooling. For proper air circulation, it is also important to replace any slot covers on the back of a computer that may be missing as a result of removed expansion cards.