Confused: How PCIe 2.0 and 3.0 works?

iamnottom

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If I have a motherboard that has both PCIe 2.0 and 3.0 and I plug something into a PCIe 2.0 slot but not the 3.0 slot, will the motherboard just use the PCIe lanes associated with a motherboard's chipset?

From what I understand, a CPU can have lanes for PCIe and a motherboard's chipset also has lanes for PCIe. Does this mean you can use one without it affecting the other?

Here's an example to clarify my question: Let's say I have a motherboard with a Z97 chipset. If I plug a GTX 970 into the motherboard's PCIe 3.0 x16 slot and an older R6 265 into the PCIe 2.0 x16 slot, will these both run utilizing the 16 3.0 lanes from the CPU and 8 2.0 lanes from the motherboard's chipset?

Also, just for clarification: when referring to PCIe 3.0 x16, does the "x16" just refer to the length of the slot and the number of lanes is implied based on the specs?

Thanks for any answers I receive in advance.
 

iamnottom

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Aug 27, 2015
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Thanks for the reply. I came across that article before and it didn't quite answer my exact question.

I should clarify. I am aware that there will not be much of a difference between 2.0 and 3.0 with most GPUs currently available on the market. I am not worried about the performance being degraded between 3.0 x16 and 2.0 x 8. And I don't think I'll ever be enough of an enthusiast to look into SLI/Crossfire. This question is for me to figure out how PCIe lanes are decided used based on certain configurations.

To the best of my knowledge, it's not possible to SLI/Crossfire two cards if you have one plugged into a 3.0 and another to a 2.0, much less two different model cards. But if I plugged in two cards (one each to 2.0 and 3.0), would the x16 slot turn into an x8 slot because the motherboard detects two cards? I am specifically curious about that 3.0 slot.