Compared to the Northbridge, the chipset's Southbridge component provides support for a wide variety of devices with many differing bus speeds and designs. Control over secondary buses -- USB, IDE, PS/2, Ethernet -- is the Southbridge's domain; if a new interface technology like IEEE 1394 FireWire or Gigabit Ethernet is announced, chances are that it'll show up in a Southbridge.

It's certainly nice to have access to the newest technologies, but the performance of the Southbridge is not to be overlooked. Hard-disk transfer rates are one of the most common system bottlenecks, and if an enhanced Southbridge offers faster burst-mode transfers or better use of on-drive cache, then overall application response will improve. Intel chipsets use a relatively slow 266MB/sec interface between the Northbridge and Southbridge components, but at the same time are well-known for first-class IDE performance levels. This would seem to be a paradox, but really illustrates once again that efficient use of available resources is key to winning at the chipset game.

The process of integrating additional features into the chipset (usually meaning the Southbridge), as opposed to other motherboard chips or expansion cards, seems to be moving ever faster as system integrators try to hit ever-decreasing price points. By integrating peripheral functionality into the chipset, many times all that is required for a basic PC platform is a motherboard with memory slots.

Examples include standard Southbridge features such as LAN and USB adapters and audio, which replace dedicated hardware and allow motherboards to reach incredibly low per-unit prices. Some motherboard vendors such as ECS have made integration their bread and butter, making many of their designs a perfect fit for low-cost home or business desktops.

Alternatives to AGP Cards

Perhaps the most radical departure -- and one of the only integrated features affecting the Northbridge, since it requires direct access to system memory -- involves on-chip graphics. The biggest popularizer of this cost-cutter, Intel, recently updated its "Extreme Graphics" with the 845GE and 845GV, while both VIA and SiS are reportedly hard at work building chipsets that incorporate their latest Savage3D and Xabre graphics cores, respectively.

The mover and shaker in this category continues to be Nvidia, whose nForce and nForce2 are arguably the only graphics-built-in chipsets that deliver performance on par with at least entry-level dedicated graphics cards. The speed of integrated video depends on a great many factors, from graphics core specifications to memory bus design and (since some system memory is borrowed for the display) DDR speeds, as well as support for Microsoft's DirectX 8.1/9.0 and other 3D and multimedia APIs.

But again, with the nForce products as an exception, most integrated graphics to date have been more suitable for economy models than high-performance PCs, for office productivity applications rather than image or video editing or 3D gaming. The reason it'd be nice for home-PC shoppers to know whether their prospective purchase uses an Intel 845G or 845GL, for example, is that while neither will set Quake III Arena or Unreal Tournament on fire, the latter doesn't support an AGP slot while the former at least makes graphics upgrades possible.