SLI Testing - Asus P5N32 vs. MSI P4N Diamond
From the low-quality gaming benchmarks, we're now going to move on to some more demanding tests using a pair of 7800GTs in SLI mode. For these tests, we will only be using the MSI P4N Diamond with the original n4Force-SLI chipset and the Asus P5N32-SLI using the updated n4Force-SLI X16. Basically, what we're looking for here is some evidence that upgrading from 16 to 32 PCI-e lanes improves performance. We will stick with two of the more demanding graphic engines; Doom3 and Far Cry.
Raising the resolution and enabling driver optimizations such as anti-aliasing places much more strain on the graphics cards than our earlier tests. As the games get much more advanced, using more powerful shaders and real-time physics, access to available CPU and Memory Bandwidth becomes much more vital. When the AGP bus became the bottleneck, manufacturers turned to PCI-e to help alleviate this issue. Using two GeForce cards in SLI mode further improves performance by having two cards tackle the job of one.
However, original nForce4-SLI boards didn't offer any increase in the number of PCI-e lanes over other Intel and AMD-based boards, splitting up the 16 lanes that were available. Asus' P5N32-SLI comes with 32 lanes thanks to the updated nForce4-SLI X16 chipset. In our testing of two popular games using two 7800GTs in SLI mode, we can see a small, yet favorable increase in frame rates with the P5N32-SLI. Typically, we were looking at about a 5-10 fps difference. It might not be enough for current nForce4-SLI owners to make the upgrade, but new system builders, especially those who bleed benchmark numbers, would probably find reason to start here.