Motherboard

A computer is made up of many different parts. The motherboard is the piece of hardware responsible for connecting all those parts together.

The critical piece of a computer is its processor (CPU). It fulfills the same need that our brains do: it does all the "thinking" for the computer. However, a brain by itself is pretty useless: it can think about a lot of things, but it doesn't have any means to communicate (mouth), manipulate (arms and legs), or even receive input (eyes, nose, ears, tongue, skin). This is why we have bodies, which are connected to the brain by our nervous system.

Similarly, if a processor is a computer's brain, then the motherboard is like its nervous system. However, instead of controlling arms and legs, it interfaces with:

• Your CD/DVD drive
• Your hard drives
• Your RAM
• Your video card/sound card, if you have one. If you don't, these will be physically integrated into the motherboard itself.
• Your ethernet card (for connecting to the network)
• Your mouse
• Your keyboard
• Any peripheral such as a USB flash drive, printer, or digital camera.

The specific layouts of motherboards very depending on the manufacturer, but they all look something like this:

1. This is where your processor lives. In an already built computer, this area will be obscured by a large metal heatsink and cooling fan. Pretty much anything that happens in your computer must pass in or out of this interface at some point.
2. DIMM slots. This is where your RAM (your computer's version of short-term memory) is connected to. Communication between the processor and RAM is very important, so they are usully very close to one another.
3. IDE slots. Your CD/DVD drives and older IDE-type hard drives connect here.
4. SATA ports. A newer interface for hard drives.
5. Expansion slots. Used for adding video, sound, and network cards (and more) to your computer.
6. I/O (Input/Output) ports. This is where your mouse, keyboard, and USB/Firewire devices plug in. If the motherboard has integrated sound, video, or networking, it will have ports for those as well. Older motherboards will still have serial ports.

Chipsets

Number 7 is very important to the motherboard. Let's move away from the biology analogy and instead imagine that there are railroad tracks leading to each one of the previously mentioned areas. Now, each of these needs to connect up to the processor somehow, but image that the processor only has one "track" going into it (the front side bus).

To fix this problem, your motherboard has a northbridge and a southbridge (7), which consolidate all the incoming data into one stream. Similarly, when the processor sends data back, the two bridges route it to whichever "part" it was supposed to go to.

The northbridge is much closer to the processor and is responsible for the "busiest" pieces of hardware: specifically your video (whether it be integrated or on a discrete "card") and RAM*. Other, slower items such as hard and optical drives (3 + 4), slow expansion slots (some of 5), and user interface (6) go through the southbridge, which is in turn connected to the northbridge. The combination of your motherboard's north- and southbridge is referred to as its chipset. Some chipsets, such as the nForce4 (pictured above), are single-chip designs, meaning that the northbridge and southbridge are integrated together into one chip. In other cases they are two discrete chips on the motherboard.

The image to the right is the chipset diagram for an older AMD Athlon processor which uses a discrete north- and southbridge (this southbridge does not support SATA). It may seem strange that 5 appears to be connected to both the north and south bridges: this is because there is a "special" expansion slot on motherboards, reserved for video, that connects directly to the northbridge since graphics applications tend to be extremely resource-intensive. All other expansion slots route through the southbridge.

A processor will be compatible with more than one kind of chipset. For example, the AMD Athlon64 works with nVidia nForce3 and nForce4, as well as the VIA K8T800PRO? and K8T890? .

*Note: New AMD64 processors have on-die memory controllers, so AMD northbridges are not responsible for RAM.