Guided Tour Of A Motherboard

Guided Tour of a Motherboard A motherboard is the most critical part of a computer system. It consists of three major components: the Basic Input/Output System (BIOS) chip, the Central Processing Unit (CPU), and the system buses. The initial settings for operating the system at power up are stored on the BIOS chip. These settings are backed up by a small battery. This battery is usually round and approximately the size of a quarter. The BIOS contains settings for the size and location of the boot device, the I/O specifications for peripherals connected to the Peripheral Component Interface (PCI) bus, and other settings that must be maintained when the computer is powered down. The CPU is the brain of the computer. It does all the processing for all the programs in the system. The CPU also acts as a traffic cop by relaying information to and between individual system components. Every component in the computer must be able to communicate with the CPU through the motherboard. This is done via a collection of copper or gold tracings attached to the motherboard. These tiny wires are called buses. These buses are explained in more detail below.

All functions of the motherboard are controlled by a chipset. The chipset determines resource allocation on the motherboard. The BIOS chip is a part of the chipset. Many modern motherboards contain network, sound card, and video chips intended to replace plug in PCI devices. These are all considered a part of the chipset.

System Buses A motherboard has the following buses connected to it:      

The power bus The front side bus The back side bus The Peripheral Component Interface (PCI) bus The Universal Serial Bus (USB) Firewire bus

The Power Bus Power for the system is distributed by the motherboard. This is done via a power bus that is connected to the power supply. The power supply is mounted in the case separately from the motherboard to allow better heat dissipation, thus preventing critical components on the motherboard from overheating. Some components (especially disk drives) are designed to draw their power directly from the power supply instead of through the power bus. Other components, like PCI cards and USB devices, draw power directly from the power bus. The Front Side Bus

The front side bus is a special high speed bus designed especially to connect the CPU to components with which it must communicate very frequently. Examples are the Random Access Memory (RAM) and the system’s video card. The Back Side Bus The back side bus is a special bus that allows communication between the CPU and the layer-2 cache, which is a device that offloads some specialized computing tasks to make the CPU operate more quickly. Nothing besides the cache and CPU are connected to the back side bus. The PCI Bus The PCI bus is a slightly slower bus that connects many optional cards to the motherboard. Examples of these include sound cards, network cards, and custom manufactured external peripheral cards. There is a newer PCI standard, called PCI Express, which is designed to handle inter-card communication at multi-gigabit speeds. The USB Many external peripherals are connected to the system via the USB. The list of these items include printers, scanners, cameras, network cards, mp3 players, external hard disk drives, and many more items. A lot of people prefer USB devices because they are easier to connect to the computer, they can be "hot-swapped," and you don't have to have separate power supplies for each external device. There are two USB standards: USB 1.0 and 2.0. USB 1.0 is not used on newer computers because USB 2.0 is backwards compatible. Firewire Firewire is a special bus designed to operate very efficiently with cameras and other peripherals that require an extremely high speed, wired interface. USB 2.0 is minimally faster than USB 2.0 (firewire operates at 400Mbps and USB 2.0 is 480Mbps). There is a newer firewire standard that allows for component operation at 800Mbps. Special Features of a Motherboard The following pictures depict special features of a motherboard that you should be able to recognize: This is the CPU socket or the location where the CPU is connected to the motherboard. The CPU frequently has a fan mounted on top of it when installed, so this socket may be difficult to recognize if the CPU is already installed. These are PCI Express slots. This is a newer version of the PCI standard that allows for insertion of peripheral boards that communicate at extremely high data rates. These are standard PCI slots.

These are Random Access Memory (RAM) connectors. RAM is used by the processor to temporarily store data while the CPU is working on a computation.

The grey connector in this picture is where an ATX power supply connects to the motherboard. The black connector is for a floppy disk drive. These are IDE connectors. IDE connectors are mainly used for connecting hard disk drives to the system. Each IDE connector can accommodate up to two IDE drives. Sometimes CD-ROM and DVD drives are IDE devices. These are Serial ATA (SATA) connectors. SATA devices are beginning to replace IDE devices in systems. These are USB 2.0 connectors. These are firewire connectors. Peripheral Connectors Many newer motherboards have multiple connectors attached to their side for connecting peripheral or input/output devices. Examples of these ports are shown below:

From left to right these connectors are: PS/2 Mouse

Parallel Port

RJ-45 RJ-45 Line In Ethernet Ethernet

PS/2 Serial S/PDI Firewire Keyboard Port F Out USB

USB

Rear left/right speaker

Microphone S/PDIF Out

Summary A motherboard is a fairly complex device, but is easily understandable if you break it down into component pieces. Everything in a computer must connect through or to the motherboard. All of these connections are made via a series of wire traces referred to as buses.