SLI can reduce fps

I have tested several nvidia-systemsettings with 2 GTX 680, and I noticed that running them on SLI can have lower fps than using only one for rendering.

This seems to occur in missions where the CPU (i7 3770K @ 4,6 in my case) is heavy on stress because of lots of AI going on on Altis and I only had around 30fps, enabling SLI in this case reduced fps to around 25. In simple missions (like the BI presentations) where the CPU is not bottlenecking, SLI increases fps by around 25-30%.

I guess running 2 cards on SLI on 2 PCIe slots produces some overhead that means a little more stress for the CPU compared to just handling one card.

But as Arma3 is very often limited by CPU power, I'd say that it's better to have one top graphic card than 2 in SLI.

Using one exclusivly for phyxs didnt give me any fps gains, at least when running around as infantrist.

Did anybody experience the same?

Yes as you said, one good gpu is much better than 2 lower ones especially for arma.

SLI used to give me much better fps on arma 2 with a profile thing I DLed, but one gpu burned out more than a year ago, I never got to test that for arma 3.

I have a gta 560ti 2gb, 800mhz load

Used to have 2 in sli, only one now

SLI is kind of shitty sometimes, it gives performance boost but it's better to get just one good card, who wants to get rid of 2 cards when you want to upgrade, it's too much investment lol

Anyway overall arma 3 I have heard has bad/no/limited etc sli support (heard 30 different things)

Well not only that one good GPU is better than 2 lower ones... even 2 TOP GPUs will be worse than only 1 of those top GPUs!

SLI can be really counterproductive if the CPU is bottlenecking (which it is most of the time as ARMA3 is bad multithreaded and Core-0 is limiting)

For me, not playing altis helps.

Altis is pretty much not optimized at all, I get much better fps on mod maps

For me, not playing altis helps.

Altis is pretty much not optimized at all, I get much better fps on mod maps

Well Altis is huge... I dont think any Mod-Map is that big!?

Yeah they have maps that big.

Some are kinda empty, but many arma 2 maps are big and have much better,fps.

Also the size of map doesn't matter that much dude, altis is mostly big repeated stuff anyway,it could be half the size and pretty much the same.

For arma2 maps to use in arma 3 (with a3mp mod or aia terrain pack) I personally like torabora

All in arma terrain pack is a standalone mod, let's you play any arma 2 or arma 1 maps, it comes with some excellent maps from those old games.

It's like 6.something gb tho

I have tested several nvidia-systemsettings with 2 GTX 680, and I noticed that running them on SLI can have lower fps than using only one for rendering.

This seems to occur in missions where the CPU (i7 3770K @ 4,6 in my case) is heavy on stress because of lots of AI going on on Altis and I only had around 30fps, enabling SLI in this case reduced fps to around 25. In simple missions (like the BI presentations) where the CPU is not bottlenecking, SLI increases fps by around 25-30%.

I guess running 2 cards on SLI on 2 PCIe slots produces some overhead that means a little more stress for the CPU compared to just handling one card.

But as Arma3 is very often limited by CPU power, I'd say that it's better to have one top graphic card than 2 in SLI.

Using one exclusivly for phyxs didnt give me any fps gains, at least when running around as infantrist.

Did anybody experience the same?

Try and leave object detail to standard and object view distance not more than 1,5k or so for infantry. You can max out the other details, including resolution scale, FSAA, etc., but keep and eye so you don't go beyond that 2GB vRAM per card that you have (of there are 4GB versions of gtx680, should be much of a problem).

If the game sends two draw calls for each card although it renders the same image, instead of one draw call, then in the current API could appear a bottleneck - or the AI and the rendering part are bottlenecking themselves asking for CPU time on a not so much multithreaded code.

Also, nvidia used to have a setting called render ahead in the driver, try to play with it, because it can give some boost in FPS at the expense of frametimes consistency. In theory at least.