How does pci-e 2.0 and 3.0 work?

Just a few questions on pci-e 2.0 and 3.0 as it's nearing the awesome release of some beastly (but possibly expensive -.-'') new 79xx series cards.

1. Let's say I have a board with two pci-e 2.0 x16 slots (x8 if crossfire, correct?), and I end up getting something like a 7950. Would there be enough bandwidth? I keep hearing people say that pci-e 3.0 is highly unneeded. If the one pci-e 2.0 x16 is borderline enough for the 7950, would I not be able to crossfire it without bottlenecking a ton?

2. Now let's say I have a board with two pci-e 3.0 x16 slots (isn't 3.0 supposed to be x32? or is the "pci-e 3.0 X16" irrelevant with bandwidth?), I can use cards like a gtx 580 or 6970 in crossfire on them still and it would just be an unnecessary amount of extra bandwidth?

Thanks in advance for your help.
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  1. In order to use PCIe 3.0, you will need a 3.0 graphic card, a mainboard that supports PCIe 3.0, and a 22nm CPU. If any of those components are missing, you won't get PCIe 3.0 speeds. PCIe3.0 is supposed to reach 32GB/s in x16 mode while PCIe2.0 only reaches 16GB/s in x16 mode and it is backwards compatible with PCIe 2.0 and 1.0 devices. Basically, you are just future proofing, if you are buying a PCIe 3.0 ready mainboard now. As far as crossfire and sli go, I read someone here in the forum that it will function the same. Just like a PCIe2.0 sli or crossfire, you will see increased performance(depending on your system set up) as opposed to a single card. Supposedly, it will be x8 in crossfire/sli just like the 2.0 devices just with faster speeds, because of the improved architecture.
  2. jik771971 said:
    In order to use PCIe 3.0, you will need a 3.0 graphic card, a mainboard that supports PCIe 3.0, and a 22nm CPU. If any of those components are missing, you won't get PCIe 3.0 speeds. PCIe3.0 is supposed to reach 32GB/s in x16 mode while PCIe2.0 only reaches 16GB/s in x16 mode and it is backwards compatible with PCIe 2.0 and 1.0 devices. Basically, you are just future proofing, if you are buying a PCIe 3.0 ready mainboard now.

    z68 gen3 mobos has pci-e 3.0 but are 32nm with sandy bridge then how you say with 22nm pci-e 3.0 are fine for 32nmn also :kaola:
  3. pro-gamer said:
    z68 gen3 mobos has pci-e 3.0 but are 32nm with sandy bridge then how you say with 22nm pci-e 3.0 are fine for 32nmn also :kaola:


    I think he misspelled the word.
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