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Radeon HD7950 x PCI-Ex 1.1 Slot - Significant Bottleneck ?

  1. #1

    Radeon HD7950 x PCI-Ex 1.1 Slot - Significant Bottleneck ?

    Some time ago I bought an ATi Radeon HD7950 3GB 384-Bit for my quite old system. I did have a huge performance gain moving from HD6870 to HD7950, but I'm not sure how far the board interface may be bottlenecking my card. My mobo has 2 PCI-Ex x16 v1.1 slots, what means that each slot operates @ 4GB/s.

    I found an article telling that the performance loss using one PCI-Ex 3.0 high-end single GPU card in a PCI-Ex x8 v2.0 (4GB/s) interface is very small for most games; so I guess it's the same for a PCI-Ex v1.1 x16.

    Moving from PCIe 2 x16 (8GB/sec) to PCIe 2 x8 (4GB/sec) incur a generally very small penalty on the 7970. However like most tests this is entirely dependent on the game itself. With games like Metro 2033 the difference is non-existent, while Battlefield 3 and Crysis only lose 2-3%, and DiRT3 suffers the most, losing 14% of its performance. DiRT3s minimum framerates look even worse, dropping by 19%. As DiRT3 is one of our higher performing games in the first place the real world difference is not going to be that great its still well above 60fps at all times but its clear that in the wrong situation only having 4GB/sec of PCIe bandwidth can bottleneck a 7970.
    Source: AnandTech - The Radeon HD 7970 Reprise: PCIe Bandwidth, Overclocking, & The State Of Anti-Aliasing

    What are your thoughts? Am I burning money?
    Last edited by vrosa; 22 Feb 2013 at 15:12.

      My System SpecsSystem Spec

  2. #2

    A PCI-E 1.1 X16 slot would support the same data rate as PCI-E 2.0 X8, or PCI-E 3 X4.

    Short answer: negligible effect, most of the time. Small effect, the rest of the time.

    Maybe the QX9770 is limiting things on its own, interfaces aside. In the US, it's be practical to upgrade to an I7-3770k, good midrange Z77 motherboard, and 8GB of DDR3, for about twice the cost of the HD 7950. If you wanted an I7-3930k, plus 16GB of RAM (4x4GB), it's be more like 3X the cost of the 7950.
      My System SpecsSystem Spec

  3. #3

    Good to hear that ! I will keep that rig as it is. My interest now is to invest my budget in a 6-core i7 system.
      My System SpecsSystem Spec

  4. #4

    Quote Originally Posted by vrosa View Post
    Good to hear that ! I will keep that rig as it is. My interest now is to invest my budget in a 6-core i7 system.
    Seems like a good idea. (See my system specs.)

    NVidia has had some issues with PCI-E 3 on X79 boards, but AMD supports it.
      My System SpecsSystem Spec

Radeon HD7950 x PCI-Ex 1.1 Slot - Significant Bottleneck ?
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