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PCI Express 3.0 Has Zero Performance Incentive for Radeon HD 7970: Tests

Discussion in 'News' started by btarunr, Dec 22, 2011.

  1. btarunr

    btarunr Editor & Senior Moderator Staff Member

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    Over the last few months, motherboard manufacturers have been raising a big hoopla over how it's important to pick their products that feature PCI Express 3.0 (Gen 3.0) slots. There was even some drama between competing motherboard manufacturers over who was first to the market with this technology, even when consumers couldn't really make use of the technology. To begin with, you needed a next-generation Ivy Bridge CPU, then you needed a compliant graphics card. Sandy Bridge-E, fortunately, formally introduced the technology, complete with motherboards and processors that support it.

    GPU maker AMD wanted to be the first to be out there with a GPU that's compliant with this interface, and so one thing led to another, and VR-Zone got to set up a test-bed using Core i7 "Sandy Bridge-E", ASUS Rampage IV Extreme (which allows users to change PCI-Express standard mode in the BIOS setup program, by forcing Gen 2 or Gen 1 mode), and an HD 7970, to see if running the GPU on PCIe 2.0 and PCIe 3.0 modes made any worthwhile difference. The results are in: zero, nada, zilch, sunna (zero in my language).

    [​IMG]

    In its comparison, VR-Zone put the GPU through 3DMark 11 (a DirectX 11 graphics benchmark) and ComputeMark (a GPU compute shader benchmark that heavily loads system bus). The performance figures between the two were agonizingly insignificant. 3DMark 11 and ComputeMark are tell-tale tests of whether the GPU (and with it, its system interface) is at least getting loaded enough. You would much rather spend the money you saved to upgrade your current, perfectly-functional LGA1155 motherboard to an "ooh-Gen3" one, on a memory upgrade, before DRAM prices rebound.

    [​IMG] [​IMG]

    One area, however, where Gen 3.0 could have a performance incentive, could be with future Ivy Bridge LGA1155 platforms, where to run 2-way CrossFire, the single x16 link from the CPU is split into two PCI Express 3.0 x8 links. Those numbers could be interesting.

    Source: VR-Zone
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  2. loleafidas New Member

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    The current GFX can't use maximum bandwidth of PCIE 2.0, so how can they make a difference on PCIE 3.0?
  3. laszlo

    laszlo

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    they can in your pocket....e-peen had sometimes a major buying decision :laugh:
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  4. SteelSix

    SteelSix

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    Yeah this one was an e-peen festival from the manufacturer standpoint; they were lining up to compare peen's while we were like WTF, another same model board? What's the difference?
  5. Hayder_Master

    Hayder_Master

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    I think nvidia will be work on that, other thing i see 7990 will use pci-e 3.0
  6. Live OR Die

    Live OR Die

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    There probably using a old bios 1005 which isn't released on the asus website has

    update microcode, pcie gen 3.0 codes

    Which are probably needed.
  7. Over_Lord

    Over_Lord News Editor

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    yet again if HD7970 wouldn't have supported PCIe 3.0, it would have definitely gone into the negatives of many reviews.
  8. R_1

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    Don't know if it is fair comparison, because SandyBridge CPU has only 16 PCIe lines for external GPU, where SB-E got 40 PCIe lines. So ASUS probably hardwired them as 1x16 + 3x8 in Z79. That configuration benefits old PCIe 2.0, because 1x16 graphics slot has always 16 PCIe lines connected to it, where SandyBridge mobo will implement for primary graphics only 8 PCIe wired lines + another 8, by switching IC, if another external GPU is nod conected. If that switching IC is Gen2, then it cann't operate in PCIe 3.0 CPU environment and no additional 8 PCIe can be added.
  9. mum1989

    mum1989 New Member

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  10. Grings

    Grings New Member

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    This is the only situation i was expecting any improvement in anyway
  11. punani

    punani

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    um.. anandtech says otherwise:
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  12. repman244

    repman244

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    However that is only the case with GPU computing and not with gaming AFAIK.
  13. Aleksander

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    I dont really think this is true
    See the facts:
    PCI-express 2 has at max 80GT/s
    The card itself has 137GT/s
    It can be an asus program failure too or bad programming
    Look at pci-express and make a difference with 7970 in gpu-z
    http://en.wikipedia.org/wiki/PCI_Express
  14. von kain New Member

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    wait for a crossfire bench.
  15. DanTheBanjoman Señor Moderator

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    And all that data has to go over the bus? I don't think so.

    It's no surprise, new standards never get utilized right away. They simply have to be there for companies to adopt and later on they will have added value. Same was true for PCI to AGP (banshee PCI or AGP, which is faster?), then to various AGP standards and then AGP vs PCIe, then PCIe 2.0 and now 3.0. All I can say is "doh".
  16. Aleksander

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    So you mean that the card is not giving its full potential?
    Because of the bus?
  17. sneekypeet

    sneekypeet Unpaid Babysitter Staff Member

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    I bet MSI would argue these findings....there had to be some reason to slam Gigabyte as hard as they did when they called them out for not having it, like it was the end of PCI-e tech as we knew it without 3.0 on a board:roll:
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  18. DanTheBanjoman Señor Moderator

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    No, I'm saying it's not sending the amount of data you list over the bus. Thus it is not relevant.
  19. claylomax

    claylomax

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  20. R_1

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    People are reporting 24% difference in Mediashow Expresso between PCIe 2 and 3 mode on Z79, so here it is. :laugh:
  21. red-die New Member

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    PCI-E a AGP?

    dudes...guys... bro...

    pci-e is not for GC only
    so the development are not for GC exclusive

    GC has been always have the best performance when the standard become common
    not as a pioneer in pushing it

    so the 1st pci-e 3.0 gc?
    its like moving from a cramped apartment to a big mansion,
    so much space now but it will get filled later on'
  22. Legacy-ZA

    Legacy-ZA New Member

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    This will be very handy when you start running 4x GFX Cards in SLi / Crossfire.
  23. theeldest

    theeldest

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    Also, most users have "mainstream" systems (sandybridge). I'd imagine the difference between 2.0 and 3.0 has more of an impact when your 16 lanes are cut to 8 per card in dual-GPU setups.

    And as a couple people already mentioned, makes a significant difference in compute.
  24. INSTG8R

    INSTG8R

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    Pretty much my comment on it. Pure marketing nothing more...
  25. cadaveca

    cadaveca My name is Dave

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    No CPU out there actually supports PCIe 3.0, so why is this discussion even taking place? I can set my SB-E CPU to PCIe 3.0, sure...but does it work? NO!!!

    So, the tech is not enabled fully, and you got no performance increase. Well, blow me over, I cannot imagine why. :rolleyes:


    Where can PCIe 3.0 be used, currently? INTER-GPU COMMUNICATION. Crossfire, with multiple cards. Higher bandwidth for inter-GPU communication is needed, period.


    :shadedshu
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