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P3D v3.4 HF3 performance issue with SLI

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Hi everyone,

 

Before making a big mistake, I would like to have your opinion about an issue on Prepar3D.

I changed my nVidia 780 GTX few months ago for a 1070. After the release of the latest P3D hotfix (v3.4.22.19868), I decided to invest in a second graphic card. I didn't expect a huge FPS increase, but, at least, few more fps, in particular with complex sceneries and AS16 clouds. And well ... the results are not what I expected ... It's even worse ...

I run a homecockpit based on a main P3D computer (and with 3 more computers for hardware and Prosim737 software) : 3 x 1920x1080 monitors with a i7 4770K @4.4Ghz, 16GB RAM, 2 x 1070 GTX (MSI and KFA², driver v378.78), 1 SSD for the OS (Win8.1, up to date) and 3 HDD for P3D and sceneries. I performed all my tests in France at Nantes airport with all FranceVFR Photo sceneries activated and FranceVFR LFRS. Cloud textures are from REX4 and ASCA + ENVTEX (I don't know if their textures stay in P3D folder when ASCA is not running ...). Weather is the default P3D engine (I didn't run AS16 for my tests). In term of other addons : FSUIPC, GSX, accu-feel v2 and that's all. I only run P3D on my main computer, all Prosim Modules and AS16/ASCA run on secondary computers.

On all 3 monitors, with SLI and Surround (no bezel correction) enabled, I have between 45 and 55 FPS. If I disabled Surround and SLI, FPS increase to 60-70. In therm of smoothness, it's more or less the same.
With only one monitor, it's even more obvious. No SLI : 100-110 FPS. With SLI : 60-70 fps. Something is wrong here ... I searched for the culprint, but I couldn't find it ...

To check if SLI was well activated with no issue, I tested SLI with the Unigine Heaven Benchmark on one monitor. It confirmed that SLI is working correctly on my system (a mean of 110 FPS without SLI and a mean of 180 FPS with SLI). I will test with all 3 monitors tonight.

So before I decide to sell the second 1070, do you have an idea ? I can add that P3D and OS are one month old (installed on formated SSD and HDD), all drivers are up to date, Windows updates are regularly installed ... and ... and I don't know what to do now ...

Thanks for your help, everyone !

 

Olivier

 

Original post : http://prosim-ar.com/forum/viewtopic.php?f=72&t=11592

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Olivier,

SLI does not improve anything in FSX or P3d. SLI improves other games like BF, etc. Anyone that tells you otherwise is fooling themselves and trying to justify wasting their money on another graphics card purchase.

On the other hand, If you use your PC for other games then only you can decide if the expense of an additional graphics card is worth it. Flightims need CPU power. I was so disappointed when I went SLI for flightsim based on users here touting it the holy grail for SGSS with many clouds in the scenery, what a joke. Like you, I found out the hard way. Non SLI brought greater FPS and a more smoother experience.

Fly safe.

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If you are expecting major FPS improvement using SLI, it's not going to happen. On my system however, I get increased smoothness and much less usages and heat on my GPU's. I run a 4K monitor so I have SGSS off and most sliders at or near max.

Whether the improvement on YOUR system would be worth the extra $$ - only you can make that call.

On my system I went for smoother performance and less drain on the GPU's.

Vic

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51 minutes ago, mokeiko said:

SLI does not improve anything in FSX or P3d. SLI improves other games like BF, etc. Anyone that tells you otherwise is fooling themselves and trying to justify wasting their money on another graphics card purchase.

Says you.  Pretty arrogant to suggest that anyone that disagrees with you or who has been able to make SLI work where you have not is "fooling themselves."

In my experience, SLI does not improve frame rates, but it enables me to fly smoothly at 4K res in areas with a heavy hit due to AA without stutters.  With a single GPU I start to see stutters in heavy cloud cover as the GPU load nears 100%...with two GPUs (I use a pair of overclocked GTX980Ti cards) I can get through the same scenario with little or no impact to smoothness.  The improvement is real and is worth it to me, and anyone that suggests that I am fooling myself doesn't know what they're talking about...I've experimented with both single and dual SLI configs, and the results were convincing enough that I choose to continue to deal with the other challenges of SLI (driver support issues, mostly) to get the observable benefits.  I could have deconfigured my sim machine to a single GPU and moved the other 980Ti to my gaming box when I built it, but I did not because there is a clear difference in performance on my system during ground ops in heavy scenery and when in clouds with a heavy add-on load.

Honestly, fps is a flawed measure of performance in many scenarios.  I use a 30Hz 4K display, locked with vsync.  The sim is far, far smoother at steady locked 30Hz than fluctuating between 30-45 Hz on a 60Hz monitor.  I shoot for headroom--as big as possible a gap between CPU load and max CPU load, so that occasional spikes in workload don't cause long frames/stutters.

Regards

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1 hour ago, mokeiko said:

Olivier,

SLI does not improve anything in FSX or P3d. SLI improves other games like BF, etc. Anyone that tells you otherwise is fooling themselves and trying to justify wasting their money on another graphics card purchase.

On the other hand, If you use your PC for other games then only you can decide if the expense of an additional graphics card is worth it. Flightims need CPU power. I was so disappointed when I went SLI for flightsim based on users here touting it the holy grail for SGSS with many clouds in the scenery, what a joke. Like you, I found out the hard way. Non SLI brought greater FPS and a more smoother experience.

Fly safe.

 

It all depends on your resolution, yes you could run in a single card @ 1080p  but when you get @ 8000 x 1600 triple monitors you can use all the horsepower available.

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"Whether the improvement on YOUR system would be worth the extra $$ - only you can make that call"

I totally agree with this. For the $700 more (at the time) that it cost me to get an extra 980ti, it wasn't worth it.

"Says you.  Pretty arrogant to suggest that anyone that disagrees with you or who has been able to make SLI work where you have not is "fooling themselves."

Not being arrogant at all. OP was the first person I responded to, don't know where you got that "Anyone that disagrees with you" statement. I have SLI "working". Says you, Pretty arrogant of you to make that conclusion as well. OP found out the hard way as me, just reinforcing what he now already knows. Let's see you convince him that keeping that $400 plus card is worth it. Just trying to help him salvage some money back.

"Honestly, fps is a flawed measure of performance in many scenarios.  I use a 30Hz 4K display, locked with vsync"

Nobody cares what you use it for, that is not what the OP uses so your point is moot. My response was based on what he needs SLI for. Not really difficult to understand.

Another user used to use 2 Titans in SLI and went back to one, hmmm I wonder why?

Fly safe

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18 minutes ago, mokeiko said:

Not being arrogant at all. OP was the first person I responded to, don't know where you got that "Anyone that disagrees with you" statement. I have SLI "working". Says you, Pretty arrogant of you to make that conclusion as well. OP found out the hard way as me, just reinforcing what he now already knows. Let's see you convince him that keeping that $400 plus card is worth it. Just trying to help him salvage some money back.

"Honestly, fps is a flawed measure of performance in many scenarios.  I use a 30Hz 4K display, locked with vsync"

Nobody cares what you use it for, that is not what the OP uses so your point is moot. My response was based on what he needs SLI for. Not really difficult to understand.

Fly safe

What you "found out the hard way" is your own experience.  In the hands of a competent system designer, it can and does work...your original statement that "anyone that tells you otherwise is fooling themselves and trying to justify wasting their money on another graphics card purchase" is absolutely not true.  It's a rude blanket statement that anyone who says differently than you is somehow dishonest and pursuing a self-serving agenda.  I am telling you otherwise, because it does work here, and I know it works elsewhere for others.

I've already gotten an e-mail asking about my configuration, so apparently somebody does care what I use it for.

 

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