PCIe 3.0 x8 card in PCIe 2.0 x16 slot: will it run in PCIe 2.0 x8 or x16 mode?

Andrew17857

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I've seen a number of questions asking similar questions to the above, but I couldn't see that anyone had asked my specific question yet, so here goes.

I'm about to buy a Gigabyte GV-R725O5-2GI PCIe 3.0 x8 video card.

My motherboard has PCIe 2.0 x16 slots.

My question is whether the card will run in PCIe 2.0 x16 or PCIe 2.0 x8.

Obviously, the number of lanes on the card is a physical issue (i.e. how many wires it has). So presumably, if it is PCIe 3.0 x8 it only has 8 lines, so will run PCIe 2.0 x8 on my motherboard. Is that right?

If so, will it make any practical difference on performance?

Thanks.
 

ubercake

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In almost all cases, the PCIe x16 slot closest to your CPU is the x16 slot. If you put the video card into that slot, you'll have the bandwidth of 16 PCIe 2.0 lanes to work with.

From a bandwidth standpoint:
1xPCIe 3.0=2xPCIe 2.0
8xPCIe 3.0=16xPCIe 2.0
 

Andrew17857

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Thanks for all your answers. I think the jury's still out as some have said x8, some have said x16 and some have said it's capable of running in either! My gut reaction was the same as endeavour37a's.

Looking here, as between PCIe 2.0 x8 and PCIe 2.0 x16, it doesn't appear to make any difference anyway, even for cards which are very significantly faster than the one I've bought:

http://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/

I've ordered it anyway now, so I'll see when I put it in the motherboard.

Thanks again.
 

brarboy

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enjoy for the best!!!
Post the results of cards as soon as you get it started. :D
 

Andrew17857

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I've received the card now, and confirm that it works in PCIe 2.0 x8 mode.

Also, if anyones interested I can also confirm that it works in CrossFire mode with my other card, an Asus R7240-2GD3-L, on my Dell Precision T5400 (Intel 5400 chipset on the motherboard).

Andrew

 

brarboy

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thanks for the update buddy. Enjoy!!!