Our recent analysis of three-card CrossFireX on P55-based motherboards demonstrated that the bandwidth restrictions of the third slot’s first-gen PCI Express (PCIe) x4 interface was the most likely cause of dramatic performance drops in some games, compared to an otherwise-identical dual-GPU configuration. The LGA 1156 interface’s native support for 16 PCIe 2.0 lanes (running at 5 Gb/s) across a maximum of two devices leaves the P55 chipset’s slow 2.5Gb pathways as the only means for hosting additional devices. Many of our forum members would label the attempts made by several manufacturers to add a third x16-length slot to LGA 1156 platforms as failures of epic proportions.
But what if the third slot didn’t have to rely on the platform controller hub to facilitate lackluster throughput? Certainly some other type of data hub could be devised to allow the processor’s 16 lanes to be divided three ways, with the equivalent bandwidth of five 5.0Gb lanes feeding each card, right? Alright, so the cards can't really operate in x5 mode. But surely an add-in device, if smart enough, could spread that bandwidth across eight lanes. Because the Lynnfield-based Core i7/i5's PCIe controller is only able to host two devices, the add-in part would have to present itself to the CPU as a single component, negotiating data traffic to any connected graphics cards using its own logic.
Fortunately these types of devices, called PCIe bridges, already exist. Nvidia has long used its nForce 200 bridge to “transform” the PCIe 1.1-equipped 680i SLI chipset into the PCIe 2.0-equipped 780i. While many of the 780i’s critics pointed to the northbridge as a bottleneck, the NF200 proved itself extremely capable of managing the bandwidth disparity.

And yet our previous CrossFire examination began with a PCIe performance analysis that showed a 4% slow-down between x16 and x8 PCIe 2.0 slots. Wouldn’t dropping to the equivalent of five lanes of bandwidth per card result in an even more dramatic performance decrease? Two motherboards that arrived for our recent Extreme Motherboard Shootout gave us the opportunity to find out.
- When Does 16/2=32?
- Test Settings And Boards
- Benchmark Results: Crysis
- Benchmark Results: Far Cry 2
- Benchmark Results: Tom Clancy’s H.A.W.X.
- Benchmark Results: S.T.A.L.K.E.R. Clear Sky
- Benchmark Results: World In Conflict
- Benchmark Results: 3DMark Vantage
- Performance Summary
- But Can NF200 Help X58, Too?
- P55 Triple-GPU CrossFireX, Fixed?
Nice gains with three way though.
Pretty sure if you have $1200 to dump on GPU's you would have gotten the proper platform in the first place...
Nice gains with three way though.
Pretty sure if you have $1200 to dump on GPU's you would have gotten the proper platform in the first place...
Exactly my point +1000
It DOES however prove that the chip gives a reasonable gain if games are going to demand more then they do now. The only games available that can really max out anything are crysis, WIC, total commander and that's pretty much all.
For the rest pretty good article though
I wish this review had come a week earlier, I would have gone 1156 over 1366 but at least it finally showed up. The last vestiges of X58's hold over P55 have been erased in my mind.
Now you can move on to figuring out SATA 6Gb/s for us. I know, I know I'm never pleased. Great work.
Don't be so quick with judgement. This may hold true for a single monitor, but many of us are already running 3x monitors in Eyefinity and even more will be in the near future. With 3x 1680x1050's a single 5870 is pushed well beyond it's capability to run many games even on medium settings.
I would have gladly bought an MSI Trinergy had I believed the NF200 would do what it claimed. I just didn't believe P55's x16 ondie pcie could pull it off.
Considering the performance difference, anyone could. There's no benefit in buying a X58 for gaming; just read the benchmarks.
If these motherboards where cheaper, buying a X58 for gaming would be a waste of money. But right now its price $100,00 over a cheap P6T X58, still give the big brother a fighting chance.
Also with other benifits - 6 core processors shortly, and you can pack in 50% more ram in a 1366 socket system thanks to an extra memory channel
hence overall its the same rule:
Performance = 1366
Mainstream = 1156
...but sadly, irrelevant to anyone (minus the .002% of PROFESSIONAL gamers) who has any sense of value and realizes that 3x high-end GPUS and the substation to run them are not a good use of money.
But yeah, hard to accept that when you have money for 3 video cards, you'll spend on a cheaper MoBo/Chipset for them.
Is the RAM/CPU/MoBo combo way cheaper on those platforms with the NF200 than on a X58 chipset? I think there's where the question should be headed, anyway. A Core i5 750 OCed, 8 Gigs with low timings and 3-way vids should do the trick for most of us, right? Even, a 3-way is kinda a lot under 1900x1200 =/
Cheers!
So now we're down to justifying 1366 over 1156 to only a 1k future cpu, or 1k in ram that only a handful of enteprise users would ever need? If you're thinking that you'll wait till Gulftown becomes affordable then you're looking at 18 months at which point you'll buy a new mobo to go along with it anyways.
If you haven't noticed, i7-750 edges the 920 in gaming, and the 860 edges the 920 in everything else. The last vestige the 1366 could claim performance in was tri/quad gpu solutions. That's now been erased as well.
Probably tongue in cheek, but relevant; can the traces of these mobos handle three cards that don't use PCIE power connectors?
Reminds me of the ATI 4770 which was originally introduced as a very good general purpose video card. In Crossfire mode it just happened to work reasonably well during gaming. It was by no means a stellar performer but the price made it attractive.