Installed a second 780 in my system and set up SLI. All seems well - NVidia and msi afterburner see the SLI config.

 

In this test, I enabled SLI by using NVidia Inspector and forcing AFR Friendly mode there. I did NOT rename the p3d executable.

 

Everything appears to be fine but I have one question - maybe due to my not fully understanding how SLI operates.

 

Using the EVGA Precision X to monitor the cards:

 

In heavy overcast, rain and with cloud shadows enabled - it showed that one GPU was taking the full load of 99% and the second was "idling" at 40% usage.

 

I would have thought the load would have been distributed.

 

I have two monitors connected to the primary card.

 

Is this behavior expected?

 

Thanx,

 

Vic

The goal is to spread the load almost equally among the GPUs (the primary card always works harder), but unfortunately the drivers are not perfect and depending on the app, that usually doesn't happen. Things to try. First try running one of those GPU benchmark tests and see if you get the same disparity between the GPUs. Second, check the power setting in the driver profile for the app  and see that it is on "Prefer Maximum Performance".

Probably no real driver profile for P3d. Using Furmark benchmark it split almost 50/50. Power profile s correct also. IIRC Beau (LM) mentioned something about P3D not scaling properly until Nvdidia gets a driver profile set up.

 

Thanx,

 

Vic

I believe Lockheed has advised that you will see better multimonitor performance by plugging one monitor into each GPU.

 

From Beau at LM: If you have multiple monitors and multiple views, then you'll generally be better off driving a display from each video card than using SLI. If you have 2 cards and 1 monitor than it's worth giving SLI a shot.

 

http://www.prepar3d.com/forum-5/?mingleforumaction=viewtopic&t=6352

 

Also, to enable SLI for P3D you need to use the AFR-FriendlyD3D trick Beau posted in the same thread. Bear in mind, this causes some breakage of the sim because Lockheed haven't coded the sim to buffer resources that persist from frame to frame in the separate threads GPU yet (they have said this is coming). In my sim I notice this only in special effects like vapor on the wing tips of fast moving jets.

 

I can't remember if the GPU are really 50/50. At least, both seem working ;-)

 

Example of artifact on leisure boat wake :

 

 

Visible also on this video (@ 3:37) : 

The real question is what is the experience like.  Has it improved framerates and smoothness (less/no stutter)?

The experience was just fine! I cranked up the sliders and cloud shadows and even though 1 GPU was maxed, I did not get the degrading FPS. My big problem with the AFR friendly hack is that it breaks compat with ASN.

 

I've read several posts from users who have set up a profile in NI. Going to give that a go and see how it pans out.

 

Overall SLI looks promising.

 

Vic

What kind of FPS were you getting?  The video looks stutter free.  Are you multimonitored?

 My big problem with the AFR friendly hack is that it breaks compat with ASN.

 

 

What kind of problem do you encountered ? I personnally use every ASN Beta since the first one and skip to AFR-FriendlyD3D.exe like a charm.

 

 

What kind of FPS were you getting?  The video looks stutter free.  Are you multimonitored?

 

 

I don't benchmark FPS with and without SLI (AFR-FriendlyD3D tricks). I'm not an FPS chaser and don't care about having 60 or 58 fps. Around 25 WITHOUT stutter sounds great for me. My only purpose of getting a second GPU is to maximize as best as possible, image quality.

 

I have to 22" screen connecting the same first GPU. P3D is full screen on only one monitored. Activ Sky Next and IVAP/TeamSpeak runs on remote laptop.

 

I'm still experimenting the impact of moving every cursor from High to Ultra and evaluating the quality/greater reality it raises or not.

What kind of problem do you encountered ? I personnally use every ASN Beta since the first one and skip to AFR-FriendlyD3D.exe like a charm.

If ASN is on the same system and you run the AFR hack, it will abort with the "ambient message" error. If you network ASN, you do not have this issue.

 

Vic

Hi Vgbaron,

 I have a request from you. Can you kindly give me an example of settings for N.I. I have  GTX 690 (SLI  2 x 680 gtx) and i want to try

 

Tks 

I am not at my flight system so I can't take a screen shot but

 

Run NI and select Prepar3d profile

set it to default then

 

in SLI

 

Antialiasing-SLIAA     AA_MODE_SELECTOR_SLIAA_ENABLED

# of GPU's                 SLI_GPU_COUNT_TWO

SLI Rendering           SLI_RENDERING_MODE_FORCE_AFR2

 

be sure you have SLI enabled in the regular Vidia control panel.

 

 

Good luck,

Hello,

   Thanks for advice. I did many tests these days and in summary i can draw some conclusions :

- i have good results with Nvidia driver 335.23 instead of 335.50 beta

- i have good results with SLI setup setting from Nvidia Control panel - Manage 3D Settings  - Force alternate frame rendering 2 instead of setup in  N.I.

 

Good results for me - smoothness and  least 30 - 35 FPS in EGLL or LFPG with Majestic DashQ400 

 

Both GPU was taking the load between  30%  - 85 % and memory between 1.2 GB - 1.5 GB. What is curious is that both GPU have almost the same load (ex : GPU 1 - 35 % - GPU 2 - 36 %) 

 

The only changes that i made in prepar3.cfg was 4088 for AM and FFTF = 10

What is curious is that both GPU have almost the same load (ex : GPU 1 - 35 % - GPU 2 - 36 %) 

 

 

That's how SLI is supposed to work. But with certain apps, the nVidia drivers are not perfect. Do you have all the IQ settings maxed out in P3d? If not I would try to go higher and see if the GPUs are still balanced.

 

 

 

- i have good results with SLI setup setting from Nvidia Control panel - Manage 3D Settings  - Force alternate frame rendering 2 instead of setup in  N.I.

 

 

NI exposes some additional settings that hidden in the nVidia Control Panel. Else, NI and the nVidia Control panel are equivalent.