Things are starting to pick up in the 64 bit market. New chipsets are being launched all the time, giving Christmas shoppers a multitude of motherboards to choose from this year. NVIDIA's nForce3 and VIA's K8T800, both compatible with the Athlon64 and the Athlon64 FX, have been the real trailblazers in this department. However, the competitors ALi and SiS, not about to let the grass grow under their feet, also sent two reference boards to our test lab.

Since the Athlon64 comes with a built-in memory controller, it should make less of a difference which chipset you use, or so the theory goes. However, we discovered that the theory doesn't quite pan out.

The crux of the problem is that there are two ways to build a platform for the Athlon64. NVIDIA has put all its eggs in a single-chip basket, while ALi, SiS and VIA have gone with the classic Northbridge Southbridge combo.

Making things even more complicated is that there are several different interconnects between the two chipsets: ALi's HyperTransport, SiS's HyperStreaming and VIA's V-Link. Unsurprisingly, NVIDIA, whose first nForce chipset broke new ground in HyperTransport implementations for desktop systems, has developed a single-chip solution that is also based on HyperTransport. Each of these designs has its own technical approach and theoretical bandwidth, the latter of which didn't always tally with our test results.

In addition to the differences in I/O architectures, there are other arguments for and against both one-chip and two-chip solutions. For instance, the two-chip version allows vendors to integrate Southbridges or to use one Southbridge in several chipsets.

That's not necessary a benefit, though: two chips are almost always more expensive than one component. Plus, one-chip solutions are generally not plagued by problems whenever clock speeds are high and signal delays long. That's the theory, at least.

In every actual motherboard we've tested so far, for example, the nForce3 150 has sent data through the HyperTransport channel at 600 MHz and not 800 MHz.

The candidates also offer widely varying arrays of features. Critical features include a Gigabit Ethernet interface, a Serial ATA controller, RAID support and the driver models. Now let's take a closer look at the individual chipsets.

Please note that this article was updated in January, as the latest NVIDIA driver versions increase nForce3's performance quite a bit.