GTX 1080 SLI, low GPU usage, low FPS

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LeXxXoR

Commendable
Jul 27, 2016
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I recently bought my 2 GTX 1080 to be able to play absolutely every game on the absolutely maximum settings. Sadly the FPS is fluctuation very much and is not nearly as high as they should be.

System:
Intel Core i7 6700k OC 4,69GHz
MSI Gaming M7
16GB CORSAIR KIT Vengeance (2x8GB)
Samsung 950 Pro
Samsung 850 Evo
BeQuiet PowerZone 750W
MSI GTX 1080 Founders Edition x2

Monitor:
Asus ROG PG278Q 144Hz 1440p

2 ribbon SLI bridges used instead of HB

Also captured the in game Benchmark of GTA 5 which you can se here: [video="https://www.youtube.com/watch?v=CWTYRI0bcNA"]https://www.youtube.com/watch?v=CWTYRI0bcNA[/video]

Now the Question:
Why is the GPU usage so low?
Why do I get so little FPS?
 
Solution
B
It's quite simple. The problem is, for a lack of a better word, the CPU. Not that your CPU is a problem, but the game is very CPU demanding, and in some areas, you simply are going to be limited by it. This is a common problem with high FPS gaming. Many games simply put too much demand on the CPU to allow you to get crazy high FPS. Some even push the CPU hard enough to prevent higher than 40-50 FPS at times. GTA V is one of those games.
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Jayhawker32

Jayhawker32

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Mar 5, 2015
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I feel like it's too easy to say try it with their HB SLI Bridge. I know you probably don't want to because that's just more money you have to spend but that's just one variable that we could remove. If it still performs the same with the HB Bridge then we know it's something else. That's the best I can give you, sorry.

This may be the the best I can give you.

The first is an image that Nvidia posted.

http://images.nvidia.com/geforce-com/international/images/nvidia-geforce-gtx-1080/nvidia-geforce-gtx-1080-recommended-sli-bridge-configuration.png

The second is a Reddit thread.

https://www.reddit.com/r/nvidia/comments/4m534q/psa_you_can_use_two_ribbon_sli_bridges_instead_of/

tl;dr: The HB Bridge is recommended for gaming at 2560x1440p or higher @ 120hz+, also some users reported gains between 10 - 30 FPS by using the HB Bridge over others.
 
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L

LeXxXoR

Commendable
Jul 27, 2016
4
0
1,510
I have already ordered one, but this will take some more days

Just disable SLI and the benchmark results in GTA 5 were the same as, if SLI was enable

also tested is in the witcher 3 with SLI 40 FPS in on certain scene und with SLI disabled ~60 FPS

PS:
sorry for bad english
 
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LeXxXoR

Commendable
Jul 27, 2016
4
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1,510
It seems to be an issue with two ribbon bridges, also i read that MSI afterburner could also have an impact.

i only tested this in the witcher 3 but i will try it it some other games as well

two ribbon bridges:
1) afterburner closes non overclocked 67 FPS
2) afterburner open non overclocked 67 FPS
3) afterburner open overclocked 67 FPS

one ribbon bridges:
1) afterburner closes non overclocked 73 FPS
2) afterburner open non overclocked 73 FPS
3) afterburner open overclocked 77 FPS

also the CPU has very much impact on the fps.
i have started an background download (~+7% CPU load) and the fps dropped slightly
 
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LeXxXoR

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Jul 27, 2016
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1,510



I have tried DSR and indeed the usage increased but the frame rate dropped slightly and changing the graphic settings hat no impact on that , but I think that this may be because i am not using the HB bridge

i really want to play 1440p 100+ FPS max settings
 
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O

OhhLongJohnson

Commendable
Aug 8, 2016
4
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1,510
Hi, i have the same problem you have with GTA V and Witcher 3 among others.
It turns out that gtx 1080 in SLI have a problem with gsync.
I have the same monitor you have and if i turn of gsync i shoot up to 90+ gpu usage per card. It's most likely a driver problem with nvidia.
Also if you keep gsync on and DSR to 4K or turn up MSAA to 8X with gta V you get the same fps as 1440p but 99% gpu usage per card and 4K
I have a HB bridge and on 1440p my gpu is still only at 60% usage so thats not gonna work.

I found this thread on geforce forums about it
https://forums.geforce.com/default/topic/946818/geforce-1000-series/gtx-1080-sli-low-gpu-usage-while-g-sync-enabled/

Wait it out for driver updates i gues

Greetings Rick
 
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bystander

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Dec 9, 2009
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It's quite simple. The problem is, for a lack of a better word, the CPU. Not that your CPU is a problem, but the game is very CPU demanding, and in some areas, you simply are going to be limited by it. This is a common problem with high FPS gaming. Many games simply put too much demand on the CPU to allow you to get crazy high FPS. Some even push the CPU hard enough to prevent higher than 40-50 FPS at times. GTA V is one of those games.
 
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Solution
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OhhLongJohnson

Commendable
Aug 8, 2016
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1,510


His main complaint is not his low fps but his low GPU usage wich leads to a disapointing fps , that has nothing to do with his cpu.
Like i said in my post above yours its gsync combined with sli, i have the same problem in gta V and if i disable gsync my gpu usage shoots from 60 per card to 90+ per card with the fps boost to mach it. Same cpu same everything just gsync disabled.

just goole 'sli gsync low gpu usage' and youl find lots of threads about this problem, witcher 3 also has it bad.
 
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bystander

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Dec 9, 2009
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Sure it does. If the CPU is not able to feed the GPU fast enough, or held back finishing some physics calculations, the GPU sits idle until the CPU finishes its job. Low GPU usage is almost always due to the CPU holding things back (in part due to the game). Given that he gains almost no FPS with SLI turned off, just shows there is a bottleneck elsewhere, and given that we know GTA V is CPU bound, that's almost certainly the cause.

Now if Gsync has a bug, that could also cause issues. It's definitely worth testing it without G-sync too.

Note: This is only where tested. Dips will vary throughout the game.
2847596-8988251569-gtav_.jpg
 
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OhhLongJohnson

Commendable
Aug 8, 2016
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hmm interesting, i have the same setup he does only i have an i7 5820k, but same gpu's and monitor.
if i have the game on 1440p native max settings except MSAA on 2x and gsync on i have 60/65% gpu usage per card and if i disable gsync with the same settings i get 95% usage per card.
Weird thing is tho if i keep gsync turned on and put my MSAA to 8X or my resolution to DSR 4K i get 99% usage on both cards and a higher fps? Its almost as if the more i demand from the card the better it performs.

I've seen a youtube video though of a guy running sli 1080,s with 1440p 2x MSAA on eay 140fps and i cant trigger that effect but i dont know his cpu.

 
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bystander

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Dec 9, 2009
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It does sound like G-sync may be a possible problem. In your 2nd scenerio, that is a classic bottleneck, which might be something G-sync is causing, or the CPU. When you bottleneck on something other than the GPU, turning up the resolution or settings will cause the GPU to have to work harder for the same FPS. This won't raise your FPS, so the bottleneck doesn't change, but your GPU has to work harder, so the usage goes up.
 
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OhhLongJohnson

Commendable
Aug 8, 2016
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hmmm that makes sense cause in the gsync on/off 2x msaa scenario i get a huge usage boost and also a big fps boost, but in the gsync turned on 2x vs 8x msaa i get a huge usage boost but no fps boost so thats the cpu holding it back at 2x msaa?
 
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bystander

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Dec 9, 2009
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Something is holding it back, other than the GPU. It is usually the CPU, but you mentioned it goes away when Gsync is turned off, which means there may be some artificial bottleneck.
 
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