Less FPS when SLI enabled

[alexbz 1]

Hi,

 

 

I just upgraded my PC with a GTX 980 TI SLI  (I had 780 TI SLI before)

 

With my 780 Ti the FPS where clearly more important when SLI enabled.

 

Now with 980 TI my FPS are less with SLI.

 

 

WIthout SLI

 

 

With SLI

 

 

I see that the GPU load are only 30% for each card with SLI! Why the card is so less exploited?

 

Of course without SLI the card is better exploited 50%

 

 

Do I need to do something?

 

I deleted the shaders and the CFG to be sure ...

 

Thanks

 

Dorian

[jabloomf1230 2,445]

All this shows is that something else other than the GPU is limiting frame rates. You should try increasing all the GPU-sensitive settings and sliders to the max. See if GPU utilization goes up.

[alexbz 1]

All this shows is that something else other than the GPU is limiting frame rates. You should try increasing all the GPU-sensitive settings and sliders to the max. See if GPU utilization goes up.

 

Do you mean settings in the p3d app? All is at max, FPS unlimited

[Michael Moe 494]

I see the same with medium to high settings on my SLI GTX970SC. Only pushing them with nax settings makes a gain in fps with SLI.

 

Michael Moe

[jabloomf1230 2,445]

Do you mean settings in the p3d app? All is at max, FPS unlimited

Try using nVidia Inspector and forcing higher levels of AA. 

 

I assume that you are using P3d 3.1. 4K resolution, dynamic reflections are both killers, as is using ASN with dense clouds. Also, try using as many 4096 textures as possible (clouds, gauges, buildings, runways, etc.). 

 

Anyway, what you are experiencing was predicted a year or so ago when people were clamoring for for an official SLI profile in P3d. Even though P3d makes far better use of the GPU, there are still a lot of threads bound to the CPU and this often "pins" CPU0 at 100% use.

 

Maybe Rob A. has some additional ideas on how to further stress the GPU.

[Michael Moe 494]

But you have to take smooth sim into the account. SLI  (or a TITAN X) is a must for eyecandy.

 

Right now i am at gorgeous KSQL with ORBX FTXNCA and Flightbeam KSFO and ORBX KMRY with max settings (water high and DR=low) and the SLI usage goes up to 70-85% on each card and it is so eyecandy and smooth.

 

Still doing 25-35fps in the A2A Comanche 250 and almost the same in the PMDG777  (22-30fps)

 

Will record a video later

 

Michael Moe

[Guest]

In V3.x SLI only seems to help when using NI SGSS AA ... I've brought this to LM's attention in V3.0 betas but unfortunately no response.  So I recommend not using SLI unless you're using SGSS AA or have some other need/benefit from it.

 

Cheers, Rob.

[garrett_frank 150]

SLI also requires some CPU overhead. So if you're in a scenario where you're normally CPU-limited, expected slightly lower performance.

[alexbz 1]

Try using nVidia Inspector and forcing higher levels of AA. 

 

I assume that you are using P3d 3.1. 4K resolution, dynamic reflections are both killers, as is using ASN with dense clouds. Also, try using as many 4096 textures as possible (clouds, gauges, buildings, runways, etc.). 

 

Anyway, what you are experiencing was predicted a year or so ago when people were clamoring for for an official SLI profile in P3d. Even though P3d makes far better use of the GPU, there are still a lot of threads bound to the CPU and this often "pins" CPU0 at 100% use.

 

Maybe Rob A. has some additional ideas on how to further stress the GPU.

 

 

Hi,

 

Indeed I obtain now about 43-40% GPU usage! 

 

It's much better i'm at 35 FPS now

 So the GPU is much more stressed, it compute more but the FPS are not increasing.

 

Here my NVI settings :

 

 

Is it enough?

 

In p3d setting i set the 8 MSAA, 16x anisotropic

[Guest]

 

 

Indeed I obtain now about 43-40% GPU usage! 

 

Try flying thru some Dense clouds/weather or run some high particle density FX in a complex scenery KSEA or KSFO or EGLL at 4K ... watch those GPUs gasp for air

 

Cheers, Rob.

[Raven9000 272]

Sorry, but something is not clear for me...

 

I thought FSX/P3D did not even support SLi/Crossfire to begin with. How exactly would you force(?) using it?

 

Particularly interested since I have a pair of R9 290s in crossfire.

[warbirds 555]

Yes, smog, clouds, rain will do it and peg my three 980's up to 90 percent at times. 

 

 

Rob I really love what LM has done with SLI,,,it works and really hauls (insert your favorite term).

[alexbz 1]

Try flying thru some Dense clouds/weather or run some high particle density FX in a complex scenery KSEA or KSFO or EGLL at 4K ... watch those GPUs gasp for air

 

Cheers, Rob.

 

You're right I reach the 99% with 4k but 15 fps in EGLL and heavy ASN clouds

 

With my native resolution 2560 x 1080 I'm at 25 fps with the PMDG 777  and 33 with another random plane and about 50% GPU charge.

 

 

So i'm able to increase the charge but at the expense of FPS

 

Why the GPU doen't work more to increase FPS?

 

Instead of 50% charge 25fps --->  80¨%   35fps

 

Is it due to my CPU?

 

It's a I7 4930K  OC at 4.4ghz

[jabloomf1230 2,445]

Sorry, but something is not clear for me...

 

I thought FSX/P3D did not even support SLi/Crossfire to begin with. How exactly would you force(?) using it?

 

Particularly interested since I have a pair of R9 290s in crossfire.

It doesn't support Crossfire, but it has supported SLI officially for some time now. I'm not sure, but I believe it was nVidia driver 352.86 from last May.

Is it due to my CPU?

 

It's a I7 4930K  OC at 4.4ghz

 

 

 

It's probably everyone's CPU. Take a look at the single thread performance of various CPUs here:

 

https://www.cpubenchmark.net/singleThread.html

 

Sure, one can OC them a little more, but basically they are all going to be in same general range of single thread performance. P3d does use as many cores as are available to load scenery, but one core usually limits performance. GPUs are making much greater performance strides than Intel CPUs are, as Intel previously assumed that adding more physical cores was a general panacea. But it is very challenging to write a multithreaded x86 app that doesn't use one thread to keep track of everything else. This "main" thread tends to be the bottleneck. Further, LM is still fudging around with ACES's old ESP code base, which really wasn't efficiently multithreaded in the first place. 

[alexbz 1]

It doesn't support Crossfire, but it has supported SLI officially for some time now. I'm not sure, but I believe it was nVidia driver 352.86 from last May.

 

 

It's probably everyone's CPU. Take a look at the single thread performance of various CPUs here:

 

https://www.cpubenchmark.net/singleThread.html

 

Sure, one can OC them a little more, but basically they are all going to be in same general range of single thread performance. P3d does use as many cores as are available to load scenery, but one core usually limits performance. GPUs are making much greater performance strides than Intel CPUs are, as Intel previously assumed that adding more physical cores was a general panacea. But it is very challenging to write a multithreaded x86 app that doesn't use one thread to keep track of everything else. This "main" thread tends to be the bottleneck. Further, LM is still fudging around with ACES's old ESP code base, which really wasn't efficiently multithreaded in the first place. 

 

 

yes you're right.

Autogen, taffic, even the cars on road belong to the CPU

 

CPU is the limiting factor in my case in high autogen, traffic

 

I have to deal with it

 

 

Thanks everybody