Motherboard

A motherboard allows all the parts of your computer to receive power and communicate with one another. Motherboards have come a long way in the last twenty years. The first motherboards held very few actual components. The first IBM PC motherboard had only a processor and card slots. Users plugged components like floppy drive controllers and memory into the slots. Today, motherboards typically boast a wide variety of built-in features, and they directly affect a computer's capabilities and potential for upgrades. In this article, we'll look at the general components of a motherboard. Then, we'll closely examine five points that dramatically affect what a computer can do.

A motherboard by itself is useless, but a computer has to have one to operate. The motherboard's main job is to hold the computer's microprocessor chip and let everything else connect to it. Everything that runs the computer or enhances its performance is either part of the motherboard or plugs into it via a slot or port.

The shape and layout of a motherboard is called the form factor. The form factor affects where individual components go and the shape of the computer's case. There are several specific form factors that most PC motherboards use so that they can all fit in standard cases. For a comparison of form factors, past and present, check out Motherboards.org.The form factor is just one of the many standards that apply to motherboards. Some of the other standards include:

The socket for the microprocessor determines what kind of Central Processing Unit (CPU) the motherboard uses.
The chipset is part of the motherboard's logic system and is usually made of two parts -- the northbridge and the southbridge. These two "bridges" connect the CPU to other parts of the computer.
The Basic Input/Output System (BIOS) chip controls the most basic functions of the computer and performs a self-test every time you turn it on. Some systems feature dual BIOS, which provides a backup in case one fails or in case of error during updating.
The real time clock chip is a battery-operated chip that maintains basic settings and the system time.
The slots and ports found on a motherboard include:

Peripheral Component Interconnect (PCI)- connections for video, sound and video capture cards, as well as network cards
Accelerated Graphics Port (AGP) - dedicated port for video cards.
Integrated Drive Electronics (IDE) - interfaces for the hard drives
Universal Serial Bus or FireWire - external peripherals
Memory slots

Some motherboards also incorporate newer technological advances:

Redundant Array of Independent Discs (RAID) controllers allow the computer to recognize multiple drives as one drive.
PCI Express is a newer protocol that acts more like a network than a bus. It can eliminate the need for other ports, including the AGP port.
Rather than relying on plug-in cards, some motherboards have on-board sound, networking, video or other peripheral support.

Photo courtesy Consumer Guide Products
A Socket 754 motherboard
Many people think of the CPU as one of the most important parts of a computer. We'll look at how it affects the rest of the computer in the next section.

Sockets and CPUs
The CPU is the first thing that comes to mind when many people think about a computer's speed and performance. The faster the processor, the faster the computer can think. In the early days of PC computers, all processors had the same set of pins that would connect the CPU to the motherboard, called the Pin Grid Array (PGA). These pins fit into a socket layout called Socket 7. This meant that any processor would fit into any motherboard.

Today, however, CPU manufacturers Intel and AMD use a variety of PGAs, none of which fit into Socket 7. As microprocessors advance, they need more and more pins, both to handle new features and to provide more and more power to the chip.

Current socket arrangements are often named for the number of pins in the PGA. Commonly used sockets are:

Socket 478 - for older Pentium and Celeron processors

Socket 754 - for AMD Sempron and some AMD Athlon processors

Socket 939 - for newer and faster AMD Athlon processors

Socket AM2 - for the newest AMD Athlon processors

Socket A - for older AMD Athlon processors

The newest Intel CPU does not have a PGA. It has an LGA, also known as Socket T. LGA stands for Land Grid Array. An LGA is different from a PGA in that the pins are actually part of the socket, not the CPU.

Anyone who already has a specific CPU in mind should select a motherboard based on that CPU. For example, if you want to use one of the new multi-core chips made by Intel or AMD, you will need to select a motherboard with the correct socket for those chips. CPUs simply will not fit into sockets that don't match their PGA.The CPU communicates with other elements of the motherboard through a chipset. We'll look at the chipset in more detail next.

Chipsets
The chipset is the "glue" that connects the microprocessor to the rest of the motherboard and therefore to the rest of the computer. On a PC, it consists of two basic parts -- the northbridge and the southbridge. All of the various components of the computer communicate with the CPU through the chipset.

The northbridge connects directly to the processor via the front side bus (FSB). A memory controller is located on the northbridge, which gives the CPU fast access to the memory. The northbridge also connects to the AGP or PCI Express bus and to the memory itself.

The southbridge is slower than the northbridge, and information from the CPU has to go through the northbridge before reaching the southbridge. Other busses connect the southbridge to the PCI bus, the USB ports and the IDE or SATA hard disk connections.

Chipset selection and CPU selection go hand in hand, because manufacturers optimize chipsets to work with specific CPUs. The chipset is an integrated part of the motherboard, so it cannot be removed or upgraded. This means that not only must the motherboard's socket fit the CPU, the motherboard's chipset must work optimally with the CPU.