PCI 3.0 x8 vs x16?

[Five.Stars]

Hi there, have recently moved my GPU down to slot 4 on my Asus ROG Hero VI so that the tubing on my 1080 Hybrid is tidier due to length of it and the orientation of rad requiring inlet and outlet be at bottom. The documentation for my mobo wasn't particularly clear as to whether or not it would operate at x16 or x8 speeds. The schematic and the description seemed to contradict itself. Anyway on testing it out via GPU-Z it would appear to only be operating at x8 in the lower slot. How much, if any performance difference would I likely see?

It wouldn't be a huge hassle to move the 1080 back up to slot number 2 (which is defo x16) but might look a bit untidier with tubing etc. Reason I moved it down in first place is that I realised I had rad orientated upside down with in/ out ports at top, which obviously would potentially cause issues with air being drawn in to pump.

Ideally would like to keep it in the lower slot, but not if I am going to see a large performance drop. Cheers for any advice.

 

[HoneyBadger]

Realistically, you won't notice a difference unless your benching. That said, my OCD wouldn't allow it!

 

[james_2k]

it ended up being a couple of hundred 3dmark points when i checked with my 690.

 

[OpenToSuggestions]

One of the main tech websites did a review a few years ago, so at least 2 generations ago.
They showed that 1x PCIE made <10% less performance that at full speed.
I realise I have given a crap description, so I shall try and find the link.

 

[Aretak]

http://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus

tl;dr: A 1% performance difference at most.

 

[Five.Stars]

Cool, will give that a watch and will see how I get on with it as is (need to move my pc from top shelf to do any work to it).

 

[pastymuncher]

Same board as me. Top red slot (primary) is PCI-e 3.0 16x when single card is used, 8x when running SLI, bottom red slot is PCI-e 3.0 16x physical but hardwired to 8x and the black one at the bottom is PCI-e 2.0 4x unless any of the PCI-e 2.0 1x slots are in use when it will also drop to 1x.

 

[Five.Stars]

Yeah mate, I knew that the slots would run at x8 when used in SLI, but thought perhaps either slot could be used in single card config at x16. As I say the manual isn't all that clear. On schematic it does indeed say PCIE_X8_2 which would indicate that it would run at x8. However in the box underneath with slot descriptions both slot 2 and slot 4 are listed with identical configurations.

As I say, will see how I get on. Ran a Heaven bench and got around 50 points less, so I make that around 1.6% lower. Probably not worth getting all that concerned over.

 

[Brazo]

X8 might be higher or lower than x16.

It's so irrelevant that testing error and what day of the week it is make far more difference!

 

[AdamScott85]

When you run a single card on that setup it will be x16, dual cards will be x8 x8, there is minimal difference between x8 and x16 anyway, less than 1 percent.