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

PCIe Scaling Summary

Today’s benchmarks include a wide variety of data on different games and resolutions, making it hard to keep track of the score. We're bundling those titles to give you a better idea of the general performance profile for the most common enthusiast-level monitor resolutions.

Enthusiasts on lower budgets will find a general performance loss of 2% to 4% when switching from an x16 to an x8 slot. That's not altogether bad. Some of that difference will accumulate in SLI and CrossFire configurations, and we will address that topic in a later article.

PCIe x4 slots hurt performance by an even greater amount, and the loss is most significant when using an AMD graphics card. The real shame is that, even though the performance drop is less dramatic for GeForce graphics, the x4 slots of P55 and P67 motherboards don’t support SLI due to an artificial cap imposed by Nvidia, presumably to sell more NF200s.

Performance losses shrink marginally at 1920x1080, but one can still expect a 10% to 18% drop when using a x4 slot.

At 2560x1600, the performance loss of an x8 slot drops to 1-3% as the bottleneck shifts to the GPU, rather than the pipeline to which it's connected. The x4 slot is still a poor compromise, losing 7% to 14% compared to what most of us would probably consider the proper configuration.

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  • 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.
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  • 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"
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  • ^They already did an article on that man
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  • 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.
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  • 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.
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  • 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."
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  • Yeah...my bad.
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  • 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.
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  • Looking forward to see the third article!
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  • 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.
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  • cats_pawIm 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 . 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 .
    It's...different for sure. Just about anything that can "bottleneck" graphics performance will have a greater effect on AMD GPUs than on Nvidia GPUs. CPU too slow? DRAM? PCIe? It's going to hurt Radeons more than GeForces.

    Of course, Tom's Hardware has all the cool kit that helps editors overcome those bottlenecks.
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  • Finally the x16/x4 question answered!! It got me thinking tho, since ATI allows "mismatched" cards do it matter which slot the faster card is in......
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  • Great article!
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  • feeddagoatFinally the x16/x4 question answered!! It got me thinking tho, since ATI allows "mismatched" cards do it matter which slot the faster card is in......



    that's an interesting question, like a 6950 and a 6970, would it be faster with a 6970 in the first pcie slot or the second.
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  • I'd love to know what AMD cards are doing that requires so much more bandwidth... faster memory speeds, perhaps?

    It might be worth conducting at least two way Crossfire/SLi tests more often in future with new card reviews or, at least, follow-up reviews, though I can imagine it'll delay such articles a little. Perhaps using AMD cards on P67 is limiting their scaling, even if it's already very good (with the 6000 series)? Would using two mid-range cards have the same effect?
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  • AHHHH! Good info. Can't wait for the next part!!!
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  • One thing though... No BFBC2 performance charts?

    This is a mighty popular game. Does EA make reviewers pay them to mention their game in reviews?
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  • it depends on your chipset if you want awsome scaling get a motherboard with a better chipset
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  • One nitpick are some of the conclusions, like x16/x4 don't work well for AMD, or NVIDIA. It could be correct, but you haven't proven anything in this article. Although, one could now make that case for the LGA 1155/1156 platforms, and this certainly goes a long way in showing those deficiencies, you'd still have to prove this isn't platform related, or extenuated. Your assumption is being four lanes wide is the problem, but we'd have to prove that it's not related to where the lanes are attached to before we could fully prove it's the width.

    For example, would this be the case on LGA 1366, where all the PCIe lanes are on the chipset, and not some going through the chipset and some being part of the CPU package? In real world situations, it's not so important because you'd have less cause to use an x4 in LGA 1366, but for academic purposes, and a better understanding of what's really going on, it could be interesting.
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  • So, i currently have a 5770 on w/a i5-750, obviously w/1156 chipset, would it be a good idea to get another 5770. Reason i ask is i have 2 pci express slots but second one is at 4x lanes. I have a asus p7p55d le motherboard. Do i have to buy same card or could it be a different brand at different speeds. Or better to get the 6950 2gb i want to buy.
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