I'm testing my new SLI setup, got me a second GTX480 to play with SLI taking advantage of the ridiculously low prices at which they've been selling here lately.Ok, Phil Taylor said in his blog a long time ago that the only reason why FSX cannot take advantage of SLI is because it's so CPU limited, and that it would at high resolutions and high AA levels forcing it to a GPU bound scenario.Sure enough, I can clearly see he was right. With DX10 enabled, in the VC of the PMDG 747 and in the middle of nowhere (to make sure there's not much to do in the CPU) and major thunderstorm, flying at 5000ft through thick clouds and Water maxed out at Max 2.x and AA as high as DX10 allows, CLOUD_COVERAGE_DENSITY=12, both GPU's work at 80 - 90% and I get an impressive 60% FPS gain (30 to 50 more or less)Problem is that DX10 is buggy as hell, and many AA modes don't work, like SGSS, 16xS... so what if I try something like 4xSGSS in the same scenario but DX9 intead of DX10? in spot view, same results, massive improvement 90% GPU usage on both cards... but in the virtual cockpit there is no gain at all. Both cards stay at 50% and perform exactly the same as a single card.That's a shame, but maybe I'm doing something wrong? maybe I'm missing something?I think I've tried every possible setting available, AFR1, AFR2, SFR, defaults, Single display performance mode, full screen, windowed, Vsync on and off,... Can someone please confirm if you've had any success at high AA levels or other GPU bound config, in DX9 an flying in the VC with SLI setups? meaning that you have more than 50% GPU usage and of course a performance boost compared to a single GPU setup Thanks

It looks like some default planes work. With the default Cessna, Trike and 747, in the virtual cockpit, the GPU's usage is much higher, and so are the FPS

Dfferent driver = different result on different hardware. The only driver I can use without shimmerings is the 270.61, other drivers are givings me shimmerings, I don't have SLI but I assume the same principals will apply. Here is some test I did in DX10.

Dfferent driver = different result on different hardware. The only driver I can use without shimmerings is the 270.61, other drivers are givings me shimmerings, I don't have SLI but I assume the same principals will apply. Here is some test I did in DX10.

Thanks for your input Alain. Gonna try that driver now. How do you set AA in DX10? Most modes in Inspector don't seem to work no matter what driver I use. At least I've had no success with that.I'd prefer to avoid DX10 since it's so buggy, and some addons don't even work

Yea! DX10 is buggy, the only problems I have so far are flickering runways (beside the usual stutters here and there), AA checked in FSX and here is my Nvidia Inspector settings. Some have reported good result and some did not so you may have to play with the settings, good luck.

I think I've narrowed it down to 3D gauges. I commented all of the DU gauges out of the PMDG 744's panel.vc\panel.cfg and frames went through the roof, and so did GPU usage Alain, thanks for that. It doesn't seem to work here, I still can't get SGSS to work with DX10 on, and the AG shimmer is very apparent until I switch to DX9 + 8xS + 4xSGSSSo far my conclusion is that SLI is completely usesless (barring multi-screen setups) in DX9 and the VC of any plane with 3D gauges, which is 99% of my flying time

I think SLI will be in good use for very high resolution only.

I think SLI will be in good use for very high resolution only.

I should be able to test that shortly. A friend of mine has two 23'' monitors that will be bringing to my place one of these days.Anyway, I would be very greatful if someone with 2 cards could try some huge AA settings (32xS + 8x Sparse Grid Transparency AA) in clouds and away of big airports and let me know if your cards work at more than 50% at some point or not in the virtual cockpit of a complex A/C, just to know if it's just me or not

HI Dario I can test for you. What do use use for GPU monitoring?

Thanks so much Howard!Personally, I use MSI Afterburner GPU1 & GPU2 usage % is where I check if SLI is working (apart of performance of course) at more than 50%

Dario, It looks like you have been absolutely on pint about SLI and the effects on FSX. I've always thought that even a slight improvement was beneficial. But, after seeing the results for myself, load does not exceed 40% in VC mode, I've decided to just use one of my gtx 480s and save one as a backup. It looks like SB at 5ghz and a solid card (like the GTX 480 or 580) are the keys to success with FSX. It's time to enjoy FSX!

Thank you Jose

Hi Dario Sorry for the delay - been a bit busy. Is this of any use: Let me know if you want more.

Thanks to you too Howard, that's a nice 60 something % of GPU usage! was that in DX9 mode please?

Thanks to you too Howard, that's a nice 60 something % of GPU usage! was that in DX9 mode please?

Yes DX9, windowed mode, 32xS + 8x Sparse Grid Transparency AA. PMDG 747. 5760x1200