Conclusion: "N" The Winner Is
After a look at our overclocking results it becomes pretty clear that both chipsets offer more than enough headroom for truly ballistic performance. 300+ MHz system clock speed equates to a 50% overclocking margin, and this will allow enthusiasts to tap the full potential of their components. It is not surprising that the A8N32 SLI has more headroom than the A8R-MVP, since it is the highest-end enthusiast product, while Asus decided to fit the ATI Crossfire solution into the upper mainstream. As a consequence, the board itself cannot keep up with the overclocking pace of the NVIDIA solution, even though we're pretty sure that the chipset itself could.
Then there is VIA's new K8T900 chipset, basically an offspring of the 8T890, which was the first PCI Express chipset from the chip maker. Although it splits the 16 PCI Express lanes into two x16 slots and would be able to support both ATI Crossfire and NVIDIA SLI, neither works today. Performance-wise it's up to date, and the south bridge features are comprehensive. Our assessment is that the K8T900 is an expedient alternative for those looking for a moderately priced Socket 939 platform.
From the storage interface point of view, there are two major findings. First, ULi's Serial ATA implementation offered the highest throughput of all Socket 939 solutions compared. NVIDIA was slightly behind, while ATI's SB450 brought up the rear, but an updated version is on the way for early 2006.
Our investigation into RAID 5 performance of NVIDIA's and VIA's offerings clearly disqualified the VT8251 by VIA, because the nForce4's south bridge delivers double the I/O performance, even with a degraded RAID array.
Overall, the best dual graphics chipset for AMD's Socket 939 Athlon processor family is NVIDIA's nForce4 SLI X16 - and let me underline that we did not come to that conclusion by favoring SLI over MVP. The technologies are very similar, and likely will keep leapfrogging one another with every graphics card generation, so the decision had to be made after reviewing all the other factors.
Although the nForce4 does not offer more performance than its competitors, it comes with the best feature set and software (nTune, NVRAID), large overclocking marginsm and the most powerful storage subsystem.
At the end of the day we would really like ATI and NVIDIA to agree on a common standard for multi-GPU graphics solutions. This would enable everybody to participate in this business and let the customer decide as to what he or she favors. Widely-accepted industry standards will help bring dual and multi graphics card solutions from their current place in the enthusiast market, into the upper mainstream.