The Motherboard

– Part One

When you open up a computer case you see a large printed circuit board underneath all the other components.  This circuit board is the motherboard.  The function of the motherboard is to provide power and connections to all the other components of the computer.

The motherboard (or mobo as it is sometimes called) has various sockets for inserting other cards such as video cards or audio cards.  It also has a socket for the Central Processor Unit (CPU), and this socket determines what kind of CPU can be used in the motherboard.

CPU Socket

Motherboards are usually classified by their CPU socket.  When shopping for a motherboard you will see Socket A, Socket 478, or Socket 775 for example.  The different types of sockets use different pin layouts for accepting the CPU.  You cannot fit a Socket A CPU into a Socket 478 motherboard.

When you see a name like Socket 478 or Socket 939, the number refers to the number of contacts that the CPU has.  Socket A (also called Socket 462) was the most popular type of layout for AMD processors until recently.  It is gradually being replaced by Socket 754 and Socket 939.

Socket 478 is a common layout for Intel processors such as the Pentium 4.  Intel is gradually introducing a new socket layout called Socket T (also called Socket 775 or LGA 775).

Chipsets

Chipsets are the intermediary between the CPU and the other components of the computer.  Chipsets are divided into two parts -- the Northbridge and the Southbridge.  The Northbridge is the faster of the two.  It connects directly to the CPU through the Front Side Bus (FSB).  The Northbridge also connects directly to the memory and the AGP graphics slot.

The Southbridge connects to the PCI cards, the USB ports and the hard drive.  Information from the CPU must first pass through the Northbridge to the Southbridge and finally to the external components.

Unlike CPUs, chipsets cannot be removed from the motherboard.  It is important to consider the chipset when buying a CPU/motherboard combination.  CPUs are optimized for certain chipsets, so you should choose a motherboard with a chipset that complements the CPU.

Buses

All aboard!  Computer data needs a way to travel from one component to another.  Like many people, data takes a bus.  Buses connect the various parts of the motherboard to the CPU through the chipset.  The speed of the bus determines how fast data can reach the CPU.

Bus speed is measured in megahertz (MHz) and is an important factor in computer performance.  The Front Side Bus (FSB) connects the CPU to the Northbridge so the speed of this bus is a very important specification of any motherboard.  There is a broad range of bus speeds on current motherboards -- from about 200 MHz all away up to 1600 MHz.

Memory Slots

Most motherboards will have two or three slots for memory chips, but some have up to seven memory slots.  The slots are designed to accept memory modules with a certain number of pins.  It is important to buy the correct type of memory module for your motherboard.
 
Modern motherboards are designed to accept Double Data Rate (DDR) memory, which is twice as fast as regular memory because it can be accessed on both the up and down cycles of the CPU.  DDR2 is even faster than DDR, and is quickly becoming the standard for computer memory.

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