Your motherboard choice determines the RAM and CPU types you can use, so you must look at these three critical components together. You can spend as little as $180 total on the trio and get by, but at that amount you're practically buying obsolescence. Plan to spend between $400 and $700 for a midrange or high-end system. You can either narrow your choices according to your preference for AMD or Intel processors, or just look for the best value in your price range. The real story is in the key features each motherboard offers.

Key Features

Chip set: A motherboard's chip set performs such vital functions as routing data from hard drive to memory to CPU, and making sure all your peripherals and expansion cards can talk to the CPU and one another. Manufacturers base motherboards around the chip sets, adding features like RAID controllers and FireWire ports to differentiate their boards.

The chip set also limits the types and speeds of CPUs the board can take, the type of RAM you can install, and (to a degree) whether extras like integrated graphics, sound, and USB 2.0 ports will be included with the board. Motherboards designed around the same chip set often share common features inherited from the chip set, and may exhibit similar performance. That's why knowing the vital stats (CPU and memory support, IDE controller speed, whether sound and graphics are integrated) of the chip set you're considering can help you pinpoint the differences in otherwise very similar motherboards.

CPU: Intel's Pentium 4 and AMD's Athlon XP are the two main choices. A tip: Motherboard vendors sometimes list their boards by the type of socket that accommodates the CPU--Socket 478 for the P4, and Socket A for the Athlon. In most business applications, you won't notice a big difference between systems using the fastest Athlon and P4 chips, though you will notice a big price difference. At press time the fastest P4 chip, clocked at 2.53 GHz, was going for around $650, while the speediest Athlon XP chip cost $200. Intel's Celeron and AMD's Duron chips are still available as lower-price alternatives to P4 and Athlon XP chips, respectively, but usually the small cost savings are accompanied by a large performance drop.

RAM: Most boards use DDR (double data rate) SDRAM, though a few P4 chip sets still require Rambus memory (RDRAM). DDR memory is available in a variety of speeds, and you should generally buy the fastest your motherboard allows. Motherboard manufacturers list DDR memory types according to their clock speed or bandwidth, along with other notations. From slowest to fastest, the types are: DDR200 (aka PC1600), DDR266 (PC2100), DDR333 (PC2700), and the upcoming DDR400 (PC3200).

The RDRAM picture is relatively simple because it's available only on boards using Intel's 850 or 850E chip sets. RDRAM must be installed in pairs for best performance, and any free memory slots must be filled with "continuity modules," or CRIMMs. RDRAM can be useful in high-bandwidth applications like video editing or texture-heavy 3D gaming, but it commands a hefty price premium--RDRAM costs about twice as much as DDR memory. RDRAM is currently available in two speeds, PC800 and PC1066. Spring for the latter, faster speed (and a motherboard with a chip set supporting it) if you're purchasing a P4 that runs on the 533-MHz bus. Whatever your memory choice, be sure to consider how many DIMM or RIMM sockets are on the board, and the maximum amount of RAM you can install.

Sound and graphics: Motherboards with integrated sound have become so common it's hard to find one without it. The latest models sport six-channel digital sound chips that are more than adequate for casual gaming and MP3 playback. If you want to add a sound card for better sound quality and 3D audio support, you can always disable the integrated sound with a jumper or a BIOS setting. If you plan to run the latest 3D games, you should either avoid integrated video or make sure your motherboard includes an AGP slot so you can add or upgrade a graphics card.

Storage: Most motherboards ship with an IDE controller that supports ATA/100 or ATA/133 drives. Our tests have shown that the performance difference between the two standards is negligible, so your selection here isn't a huge issue.

Boards with IDE RAID support present a more interesting choice. A typical desktop RAID system uses a pair of identical hard disks to increase performance (by "striping" data across both drives) or to provide redundancy in case a drive fails (one drive "mirrors," or keeps an exact real-time copy of the other's contents). These days, an IDE RAID controller is an inexpensive extra, with RAID-equipped boards costing as little as $8 more than their RAID-free counterparts.

Connections: Many motherboards offer ethernet, USB 2.0, and FireWire ports, and even flash-memory readers that fit in an external drive bay. So-called legacy-free motherboards ship without PS/2, serial, and parallel ports--a welcome simplification (unless you still need to connect an older keyboard, mouse, parallel printer or other legacy device).