Aside from the processor, the main component on a motherboard is called the chipset. This usually is a set of one to five chips that contains the main motherboard circuits. These chipsets replace the 150 or more distinct components that were used in the original IBM AT systems and enable a motherboard designer to easily create a functional system from just a few parts.

The chipset contains all the motherboard circuitry except the processor and memory in most systems. Because the chipset really is the motherboard, the chipset used in a given motherboard has a profound effect on the performance of the board. It dictates all the performance parameters and limitations of the board, such as memory size and speed, processor types and speeds, supported buses and their speeds, and more.

If you plan to incorporate technologies such as the Accelerated Graphics Port (AGP) or the Universal Serial Bus (USB) into your system, you must ensure that your motherboard has a chipset that supports these features. Because chipsets are constantly being introduced and improved over time.

Several popular high-performance chipsets are on the market today. The best of these offer support for double data rate synchronous DRAM (DDR SDRAM) or Rambus DRAM (RDRAM) memory, PCI and AGP 4x or faster buses, Advanced Configuration and Power Interface (ACPI), and USB 2.0 and Ultra-DMA 100 ATA (IDE) support.

Clearly, the selection of a chipset must be based largely on the processor you choose and the additional components you intend to install in the computer. Most of the better chipsets on the market today should have many features. If you are intent on building the ultimate PC (at least by this week's standards), you also should consider the fastest processors available.

Be sure not to waste your investment on the most capable processor by using a chipset that doesn't fully exploit its capabilities. When you are designing your system, carefully consider the number and type of expansion cards you intend to install. Then, ensure that the motherboard you select has the correct number of slots and that they are of the correct bus type for your peripherals.

When you buy a motherboard, I highly recommend you contact the chipset manufacturer and obtain the documentation (usually called the data book) for your particular chipset. This explains how the memory and cache controllers, as well as many other devices in the system, operate.

This documentation should also describe the Advanced Chipset Setup functions in your system's Setup program. With this information, you might be able to fine-tune the motherboard configuration by altering the chipset features. Because chipsets are frequently discontinued and replaced with newer models, don't wait too long to get the chipset documentation because most manufacturers make it available only for chips currently in production.