Cannot achieve x16/x16 SLI build

[Starstep]

Hello all,

So here is my build

Motherboard: Asrock x99 Extreme11
CPU: Intel Core i7-5930k
RAM: HyperX Fury DDR4 8gb (x4)
VGA: EVGA TitanX SC 12gb (x2)

So the issue that I am having is that after I installed the second VGA card, and using Nvidia Inspection tool, it turned out that the second card is running as x8 (not x16 as the MB supports, the first card is running x16 tho)

I followed the Motherboard instruction manual while installing the cards to achieve the dual x16 configuration; one VGA in PCIe1 & the other in PCIe4. I Used the SLI bridge that was provided with the motherboard, all drivers for the motherboard and the cards are up to date.

I have tried running both cards separately and both were performing well under benchmarking (with almost identical results)

I am satisfied with the performance of my computer right now, But I wouldn't mind juicing out every drop that I can get. So if someone out there can help me figure this issue, I would be thankful.

Have a good day

 

[Mr Kagouris]

There's absolutely no difference between x16 and x8. The only remotely noticeable difference in performance was observed while maxing out an R9 295X2 at !x4!.

 

[Leaps-from-Shadows]

...having said that, x16/x16 just feels better, even if there is no actual benefit. Placebo effect and all...

There is a new BIOS out yesterday for that board, stating improved PCIe compatibility. Recommend updating to it.

And there might be BIOS options for selecting lane width on the PCIe slots. My ASUS Z170 board has one for the PCIe x4 slot.

 

[Starstep]

...having said that, x16/x16 just feels better, even if there is no actual benefit. Placebo effect and all...

There is a new BIOS out yesterday for that board, stating improved PCIe compatibility. Recommend updating to it.

And there might be BIOS options for selecting lane width on the PCIe slots. My ASUS Z170 board has one for the PCIe x4 slot.

YES!!!!

It turns out you are correct, there has been a newer BIOS update. Downloading it caused some weird glitches in my system (which gave me a minor heart attack). But I re-installed my VGA driver again and now it's functioning normally with both cards in x16

As for the results, I am getting about 6% framerate increase in benchmarking/stress testing. not a lot, but I like gaining everything I could!

But it is strange, why did my motherboard needed an update to gain something that should be there in the stock build?

Thank you so much for your help!

 

[Leaps-from-Shadows]

Sometimes there are quirks that make some hardware not work with other hardware. Sometimes it doesn't work at all together, and sometimes they don't work at the best performance together. The latter was the case with your SLI setup. Most people wouldn't even have noticed that one card was working at x8.

Compatibility problems are fixed all the time with mainboard BIOS updates. They also do improve performance over time, as they learn over time what works best with their hardware. That's why I update to new BIOS versions as soon as they come out.