GeForce And Radeon On Intel's P67: PCIe Scaling Explored

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Intel’s Sandy Bridge-based processors dramatically advance gaming value by increasing performance at lower prices than LGA 1366-based configurations. But is the platform it sits on worthy of that CPU? We test three slot configurations to find out.

Conclusion

We found that Nvidia’s high-flying GeForce GTX 570 suffers around 2% performance loss when using an x8 slot, while the Radeon HD 6950 gives up around 4%. While noteworthy in respect to the negative impact on system value, those losses probably wouldn’t be noticeable in actual game play.

More significant are the losses when using a x4 slot, as expected. The GeForce GTX 570’s relatively significant 9% performance loss is far exceeded by the Radeon HD 6970’s 18% loss. And this is where some builders will hit an advice snag, otherwise known as self-proclaimed experts analyzing an effect and incorrectly deducing the cause.

3DTested readers often rely on each other to provide the best technical advice, and the advisor offering the most technically-detailed description often gets the nod (hey, if it sounds fancy, it's more likely to be right, right?). Unfortunately, we often see well-meaning enthusiasts leading less-experienced readers astray. Case in point: we have one pervasive poster who offers exceptionally-detailed explanations of why Nvidia graphics cards need no more than four lanes of PCIe 2.0 bandwidth, citing something about internal PCIe to PCI-X conversion. We've also seen presumed experts tell curious gamers that AMD relies so heavily on its CrossFire bridge that a four-lane slot is ideal for hosting a second card. Today’s test results prove both suggestions completely wrong. We’re hoping that today’s article will be the impetus other advice-givers need to chime-in when the community calls for suggestions on how to best configure multi-card configurations.

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Putting aside our concern for the honest knowledge-seekers, we can conclude that minimal performance losses in x8 mode set us up for the perfect logical next-step in our three-part series, where we compare X58 and NF200 solutions to today’s board. Will that 2% to 4% difference remain in SLI? Does the NF200 really hurt graphics performance by adding latency? Will the smaller performance gains of three-way CrossFireX mitigate the performance deficits of its x4 slot? Stay tuned to find out!

71 Comments Comment from the forums
  • geofelt
    These tests were done with a single card, on X16/X8/X4 slots. Fine.
    But... Who would use anything other than a X16 slot if they had one?
    The only real use for a X8 slot would be for sli/crossfire where the addition of a second card should result in an Increase of performance, not a decrease.
    Reply
  • carlhenry
    it would be nice if you included the GTX 570 in the x8/x8 and x16/x4 test. The 570 flies over the 6950 on the single card config but i was curious how it would do since i think the AMD's scale better than nvidia's. Would the 570 still lead because of its advantage? Or would AMD even it out because of its scaling (if any) "advantage"
    Reply
  • classicaxe
    ^They already did an article on that man
    Reply
  • joytech22
    Can you guy's do an article on how performance is affected if you SLI/Xfire using PCI-E 16x slots running @ 4x?

    3 way would be preferable because if performance is still adequately faster I'll consider it.
    Reply
  • dalauder
    Good comments. Can we please see 8x/8x and 16x/4x since that comparison is relevant? I get the impression that somehow SLI/crossfire reduces the performance hit of x4 lanes but I'd like to see numbers.
    Reply
  • Crashman
    joytech22Can you guy's do an article on how performance is affected if you SLI/Xfire using PCI-E 16x slots running @ 4x?I think you missed a page then!
    Http://www.tomshardware.com/reviews/pci-express-scaling-p67-chipset-gaming-performance,2887-10.html
    The numbers were there all along!

    Carlhenryit would be nice if you included the GTX 570 in the x8/x8 and x16/x4 test.Well, you should probably read the linked page too then. There's no point in artifically creating a configuration (by taping lanes or whatever) that doesn't exist in real life, is there?

    "While Nvidia prevents SLI from functioning on PCH-hosted lanes, x16/x4 configurations are completely possible in CrossFire. But should they be? We tested our motherboard in both x8/x8 and x16/x4 configurations to find out."
    Reply
  • dalauder
    Yeah...my bad.
    Reply
  • Crashman
    dalauderYeah...my bad.I didn't mean to call you out to that extent, here's a link to the forum part of this thread:
    http://www.tomshardware.com/forum/2887-56-geforce-radeon-intel-pcie-scaling-explored
    I'm going there to delete your quote from my response.
    Reply
  • rolli59
    Looking forward to see the third article!
    Reply
  • cats_Paw
    Im guessing that 8x lanes are mostly enought. I do belive that it would depend on how fast an actual gpu is, as well as how much ram it has, and how big is its bandwidth.
    I means, its logical, but mayb not true:D. Would be nice to see this test on a GTX560 Ti, since it has a lot of headroom for OC, then compare oced version vs non oced. Also this might be interesting in GPUs that have diffrent versions with more and less RAM.
    Just my 2 cents:D.
    Reply