Performance Analysis And Conclusion
Calculating average performance per game will help us to see which titles most heavily favor high-bandwidth slots.
Left 4 Dead appears to be the most significantly bandwidth-limited game, but we had previously noticed an oddity that almost disqualifies the game from further analysis. A combination of lower-bandwidth (P6T) and added PCIe latency (Eclipse Plus) could be what threw our expectations out-the-window for that title, but there’s no way of knowing the exact cause. World In Conflict appears more appropriate for analyzing the performance penalty of the P6T’s x4-width third slot, while also showing that two slots sharing sixteen pathways (Eclipse Plus) have the same performance as two x8 slots.
If bandwidth limitations to the second and third graphics card are the biggest part of today’s story, we’d expect the problem to increase with higher resolutions and details. Is this the case?
A performance difference of around 10% between the fastest and slowest PCIe configurations climbs to nearly 16% at the highest tested settings.
Tom’s Hardware doesn’t do many single-motherboard reviews, simply because it’s impossible to give every company that level of attention when faced with dozens of samples per year. Yet MSI provided an opportunity we couldn’t pass up: to access the gaming performance advantage of two shared x16 slots compared to two dedicated x8 slots. Unfortunately, we found no substantial advantage, though the Eclipse Plus remains a great motherboard in many ways that would only be completely revealed in a full review.
The real revelation of today’s article is the level of handicap an x4 slot places on the third graphics card in a 3-way SLI configuration, even with PCIe 2.0 doubling its bandwidth. We knew it would be bad, but not this bad, and the results force us to cross the Asus P6T, the DFI X58-T3eH6, MSI’s previous Eclipse SLI, and several as-yet-untested products off our 3-way SLI list. If MSI’s intent was to show how much better the Eclipse Plus is for 3-way SLI than its x16-x16-x4 predecessor, we can give the company credit for that.
What we didn’t see today, however, was whether or not three true x16 slots would provide any advantage at all over an x16-x8-x8 configuration. The reason, of course, is that the only Core i7 chipset doesn’t have the required 48 PCIe lanes, and adding a hub to “make” an x16-x16-x16 configuration leaves us with only as much bandwidth as the 32-lanes serving those three slots.
We can imagine some “Home Supercomputer” applications where Nvidia’s CUDA technology might need to access various graphics processors at different times, where the flexibility of sixteen shared pathways might be advantageous compared to two sets of eight pathways especially if three GTX 295s are used. After all, a GTX 295 on a x8 slot would only have four lanes of bandwidth per GPU. But MSI doesn’t target high-end-workstations and above with this particular motherboard, leaving that market to the competing and yet-unexamined Asus P6T6 WS Revolution. Instead it follows the path of the also-yet-unexamined EVGA X58 Classified, marketing to gamers a board that has yet to reveal any gaming advantage.
Perhaps a shootout of nForce 200-equipped X58 motherboards should be arranged, but until then, we’ll stick with the chipset-supported x16-x8-x8 configuration for our own 3-way SLI tests.