The motherboard is a very integral part of your computer system. The motherboard contains a complex array of circuits, chips, and wires. It is here that the most vital parts of your computer system are located. Located on the motherboard are the:

• Central Processing Unit (CPU)


• Memory


• System BIOs


• System Bus

Motherboards come in different sizes and shapes. Form factor is a term that relates to the physical shape and size of a motherboard. Two motherboards can have essentially the same components, but these parts can be arranged differently. Thus, the two motherboards would have different form factors. This section describes some of the more popular motherboard form factors.

AT/Baby AT:

Previously, the AT and Baby AT form factors had been the most popular motherboard form factors. However, with new technology came new, more advanced form factors.

The AT model wasn't typically used in the small personal computers found today because it was fairly wide-12 inches, to be exact. Because it was so wide, components often overlapped, which caused operating problems. The Baby AT was designed to fix this problem. It is essentially exactly the same as the AT except that it is only 8.5 inches wide, and can thus fit better in the smaller PCs.

In the Baby AT and AT form factors, the central processing unit sockets and the memory sockets are located at the front of the motherboard. Then, expansion card, which are used to add additional peripherals to the computer, were designed to extend over the processor and the memory devices. However, this produces a problem, especially with machines in which the CPU is fairly large. With big processors, the expansion cards often became blocked!

Another aspect of the AT and Baby AT form factors is that the serial and parallel ports (which are used to connect peripherals to the computer system) are attached by cables that go between the serial and parallel port connectors located on the PC case and the motherboard itself.


TX/Mini ATX:

The ATX and Mini ATX form factors were developed by Intel Corporation in 1995. They have begun to replace the AT and Baby AT form factors in the personal computer market, especially because they were designed to correct the problems and annoyances presented by the older motherboard layouts.

First, because the microprocessors and the memory devices in an AT or Baby AT form factor were located at the front, they often blocked the expansion cards. To solve this problem, the ATX and Mini ATX form factors placed the CPU sockets and the memory sockets at the back of the motherboard next to the computer's power supply. This is a good location because they will not block expansion slots, and additionally because the power supply fans can be used to help cool the microprocessor.

Another characteristic of the ATX and Mini ATX form factors is that they have the serial and parallel port connectors directly connected to the motherboard, instead of having cables like the AT and Baby AT. This helps to reduce the cost of the motherboard, improve reliability, and save installation time.


LPX/Mini LPX:

The primary goal of the LPX and Mini LPX form factors is to reduce both the size and cost of motherboards.

These two form factors have a special feature called the riser card. The riser card is used to hold expansion slots. You can plug up to three expansion cards into the riser card, which then plugs into the motherboard. Because of the way the expansion cards are connected to the motherboard via the riser cards, the height of the PC case is greatly reduced! The only problem is that this type of form factor only supports a couple of expansion cards.

Unfortunately, the LPX and Mini LPX form factors are hard to upgrade and suffer from poor cooling systems.