Simple question about PCIe lane speeds.

Hello all, long time reader first time poster.

I'm finally building my first pc from scratch, and have basically everything figured out and most of the components already bought. There is one last thing I'm unsure about, and my searching has not yielded an answer, so I figured I would ask the most tech savvy community out there.

I'm going to be getting either an ASUS P8Z68-V PRO or Deluxe which have basically the same layout. Both boards have three x16 size pcie lanes. The top two can either be run at x16/x0 or x8/x8 and the third bottom one at max x4 or x1.

Massive photo of it here.


My question: If I put my GPU in the middle (white) x16 pci-e slot, and nothing in the top slot. Will it run at full x16 speed?

The reason I ask, is I am going to have my GTX 580, along with two Blackmagic Intensity Pro video capture cards slotted in. The capture cards use PCIe x1 slots. Ideally, if you look at the way the slots are laid out: I would like to have the Blackmagic cards in the two x1 slots, and the GPU in the x16 slot just below them.

Will everything run at full speed in this configuration? I apologize if this is a really silly question. I have learned a fair bit about mobos and pci lanes and widths and limitations and whatnots but this is the last thing that I am truly unsure about.

I sincerely appreciate your time and advice.

It should be OK, the x16 and x8/x8 issue is with multiple graphics cards and I wouldn't think with just a capture card.

With that said, you would only lose 1-3% of total performance from the 580 if it was forced to run in x8 mode, so it isn't like you are dropping completely in half.

Put the GPU in the top spot. It is the only slot on the board AFAIK that will run 16. and even if you DO run 2 cards at 8 8 the performance loss is almost zero.

V and V pro of that line as well as V deluxe are VERY GOOD choices for a mobo.

If concerned get a Gigabyte UD7 board as it will give you 16/16 but through an NF200 chip. It's sort of a trick. It DOES augment the lanes but not as much as a true 16 16 link. HTH.

Others with NF200- ASUS Maximus IV Z and Extreme, ASUS WS.

1-2% performance loss from a 5870... I have been begging TPU to do this with a more modern card. If my table ever clears, Im testing and writing it up myself...

But yeah, non issue really.

Theocnoob said:

Put the GPU in the top spot. It is the only slot on the board AFAIK that will run 16. and even if you DO run 2 cards at 8 8 the performance loss is almost zero.

V and V pro of that line as well as V deluxe are VERY GOOD choices for a mobo.

If concerned get a Gigabyte UD7 board as it will give you 16/16 but through an NF200 chip. It's sort of a trick. It DOES augment the lanes but not as much as a true 16 16 link. HTH.

Others with NF200- ASUS Maximus IV Z and Extreme, ASUS WS.

Click to expand...

Ok. So as far as we know it will only run at full speed in the top slot. I'm guessing some sort of hardware switch that changes from x16/x0 to x8/x8 when anything is inserted into the second slot.

I guess I'll find out for myself in a week. Just pulled the trigger on V Deluxe this afternoon.

Thanks for the responses guys! I'll be spending much more time here learning to OC my new beast.