Graphics Card Bus interface issues

[skaloth]

Would really appreciate help.

I am running a dual gtx 970 sli setup, and all though both cards are working, i noticed lower performance than i expected. after some investigating, i noticed only one difference between the two cards. all though they are both in x16 3.0 ports, only one of them is running at x16 3.0, while the other is at x8 3.0 as seen in the images below

http://gpuz.techpowerup.com/15/09/19/nwh.png

http://gpuz.techpowerup.com/15/09/19/37p.png

i have tried many things to get this to be the same and people are saying that the motherboard is not providing as much power to one card as the other.

Any Tips?

 

[techgeek]

First off depending on the motherboard / CPU you're running it's likely that you are running X8X8 for SLI.

If you notice in your screenshots the one showing X8 is actually in PCI-E version 1.1. To get it to display properly, click the little ? beside the Bus Interface and start the renderer and select Full Screen. It should display what each card is running at. It should show X8 3.0 for each.

 

[skaloth]

First off depending on the motherboard / CPU you're running it's likely that you are running X8X8 for SLI.

If you notice in your screenshots the one showing X8 is actually in PCI-E version 1.1. To get it to display properly, click the little ? beside the Bus Interface and start the renderer and select Full Screen. It should display what each card is running at. It should show X8 3.0 for each.

I ran the test by clicking the question mark, at the bottom right the text says

" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x16 3.0"
" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x 8 3.0"

thats what the render test says both my cards are running at.

 

[maxalge]

First off depending on the motherboard / CPU you're running it's likely that you are running X8X8 for SLI.

If you notice in your screenshots the one showing X8 is actually in PCI-E version 1.1. To get it to display properly, click the little ? beside the Bus Interface and start the renderer and select Full Screen. It should display what each card is running at. It should show X8 3.0 for each.

I ran the test by clicking the question mark, at the bottom right the text says

" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x16 3.0"
" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x 8 3.0"

thats what the render test says both my cards are running at.

first pcie 3.0 x8 is plenty for that card, thats not an issue




second make and model of your motherboard?
some are limited to dual 8x 8x, or 8x 4x and such

 

[techgeek]

First off depending on the motherboard / CPU you're running it's likely that you are running X8X8 for SLI.

If you notice in your screenshots the one showing X8 is actually in PCI-E version 1.1. To get it to display properly, click the little ? beside the Bus Interface and start the renderer and select Full Screen. It should display what each card is running at. It should show X8 3.0 for each.

I ran the test by clicking the question mark, at the bottom right the text says

" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x16 3.0"
" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x 8 3.0"

thats what the render test says both my cards are running at.

So that is more like it. X8 is more than enough to run in SLI. If you're experiencing performance problems, it's not likely related to bus speed.

So lets get some more information on your problem. First off, lets get your system specs. Next what games are you experiencing performance problems with and what settings and resolution are you using in said games?

Remember that you only have 3.5GB or VRAM to use. Even though you have two cards, the effective VRAM is still only 3.5GB since both cards have to cache the same data.

 

[skaloth]

First off depending on the motherboard / CPU you're running it's likely that you are running X8X8 for SLI.

If you notice in your screenshots the one showing X8 is actually in PCI-E version 1.1. To get it to display properly, click the little ? beside the Bus Interface and start the renderer and select Full Screen. It should display what each card is running at. It should show X8 3.0 for each.

I ran the test by clicking the question mark, at the bottom right the text says

" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x16 3.0"
" NVIDIA GeForce GTX 970 : PCI-E 3.0 x16 @ x 8 3.0"

thats what the render test says both my cards are running at.

first pcie 3.0 x8 is plenty for that card, thats not an issue




second make and model of your motherboard?
some are limited to dual 8x 8x, or 8x 4x and such

The motherboard is a Gigabyte ultra durable X99-UD3

So, the x8 3.0 would not reduce fps in games and such?

 

[techgeek]

No, I've seen many articles that have discussed (including here at Tom's) PCI-E scaling for multi-GPU setups. Have a look at this link:

PCI-E Scaling

This was a quick Google of it. I'm sure you could find more. General consensus is that PCI-E bandwidth only comes into play when you are at X4.

Here is another that has SLI shown. In essence you can equate PCI-E 2.0 X16 to PCI-E 3.0 X8 since they have the same bandwidth. Very small drops in performance.

PCI-E Scaling Including SLI

 

[maxalge]

The motherboard is a Gigabyte ultra durable X99-UD3

So, the x8 3.0 would not reduce fps in games and such?

no, 3.0 x8 is plenty



according to the manual however you must use pcie_1 and pcie_2 slots when running sli and both should be x16 speeds


you might have installed the second card in the wrong slot


see your motherboard's guide

 

[skaloth]

The motherboard is a Gigabyte ultra durable X99-UD3

So, the x8 3.0 would not reduce fps in games and such?

no, 3.0 x8 is plenty



according to the manual however you must use pcie_1 and pcie_2 slots when running sli and both should be x16 speeds


you might have installed the second card in the wrong slot


see your motherboard's guide

On the motherboard they are installed in 1 and 2, but the computer is labeling them 4 and 6, which is odd as i have only three Pcie slots, would this mislabeling be causing this?

 

[maxalge]

The motherboard is a Gigabyte ultra durable X99-UD3

So, the x8 3.0 would not reduce fps in games and such?

no, 3.0 x8 is plenty



according to the manual however you must use pcie_1 and pcie_2 slots when running sli and both should be x16 speeds


you might have installed the second card in the wrong slot


see your motherboard's guide

On the motherboard they are installed in 1 and 2, but the computer is labeling them 4 and 6, which is odd as i have only three Pcie slots, would this mislabeling be causing this?

do you have a i7-5820K?

manual says PCIE_2 only runs at 8x with that cpu

this your mobo right?

you need to be using the 2 pcie slots closest to the cpu

 

[skaloth]

The motherboard is a Gigabyte ultra durable X99-UD3

So, the x8 3.0 would not reduce fps in games and such?

no, 3.0 x8 is plenty



according to the manual however you must use pcie_1 and pcie_2 slots when running sli and both should be x16 speeds


you might have installed the second card in the wrong slot


see your motherboard's guide

On the motherboard they are installed in 1 and 2, but the computer is labeling them 4 and 6, which is odd as i have only three Pcie slots, would this mislabeling be causing this?

do you have a i7-5820K?

manual says PCIE_2 only runs at 8x with that cpu

this your mobo right?

you need to be using the 2 pcie slots closest to the cpu

Yes, thats the one, ill try to switch the gpus around one more time, but thanks for all the answers

 

[Reaper_7799]

I just answered one other one like this but max is right, the 5820k only has 28 pcie lanes so it will run 1 card 16x and the other 8x. The 5930k has 40 lanes and will run 2 way sli at 16x for each card, even though your motherboard supports it, your chip determines the amount of lanes you can use. You shouldn't be able to even tell the difference though.