If you're just looking to upgrade for more performance every now and then, you can easily achieve this with mainboards from any of the three big manufacturers. NVIDIA's nForce3 is a chipset for AGP, while the nForce4 addresses the substantially growing PCI Express market. VIA offers the K8T800 Pro for AGP graphics and the K8T890 for PCI Express. Both manufacturers also address the market for high-end graphics created by NVIDIA via two graphics cards of the GeForce 6600 or 6800 families: nForce4 SLI and K8T890 Pro are the product designations for these.
NVIDIA's vision of consumers buying a graphics card of this type today, then going on to add on a second card of the same type later makes sense in principle. We anticipate, however, that within a period of 9 to 18 months it will make more sense to go with one of the newer graphics cards of the next generation. When it comes to graphics cards, 3D functionality is to a large extent what matters - not just overall performance. Therefore, if you're going to go with SLI, then it better be right now, or at least soon. Otherwise the good old 6000 series will be due for the scrap yard before SLI has had a chance to make good on all of its promises.
If you really want to play it safe, you're a regular gamer, and you expect a lot from a computer system, you should definitely latch onto an SLI chipset. Especially since the price premium over a single graphics version is usually acceptable.
Without a doubt, the nForce chipsets enjoy the best reputation in the Athlon market, since they usually leave the competition behind in terms of functionality offered. In particular, this includes the integrated network firewall called Active Armor, and the flexible RAID memory subsystem encompassing four SATA ports and two UltraATA channels. NVIDIA uses a chipset design that integrates all functions into a single chip. It claims to be excellent for overclocking, which for the most part we are able to confirm based on our own experience.
VIA, on the other hand, is still struggling with the PCI Express chipset, as the whole thing only works if NVIDIA has offered its benediction - no SLI support for VIA chipsets, no SLI. The simple K8T800 Pro and K8T890 chipsets are mature by comparison and just as fast in practice as NVIDIA products. True, operation of the components is usually a bit less convenient, and the function set is not the most extensive. On the other hand, VIA offers so-called Companion chips for common extra functions that are relatively affordable to motherboard makers as a package. This means that VIA-based motherboards have thus been less expensive.
The difficulty now facing SiS is to position itself effectively in the market given its Johnny-come-lately status. The company will scarcely be able to stand up against NVIDIA due to a lack of prestige-garnering functions. Thus the real objective will be to take market share away from VIA in the mid-range market segment by offering better value for the money.