SLI graphics

[Alpkant]

Hello I'm using SLI graphic cards and if i'm not wrong KSP not supporting SLI technology cause only 1 card working on KSP.Will KSP support the SLI?

[michaelsteele3]

What's SLI?

[KrazyKrl]

KSP is mostly bound to your CPU speed; as KSP isn't that graphically intensive. I believe that KSP will run with an SLI setup, but SLI will not increase your FPS. The biggest FPS gain in KSP would be a decent multi-core processor, with quick single cores (most of the FPS drop in KSP comes from the single-threaded physics calculations; and other game overhead that is difficult to multithread.)

SLI/Crossfire is a method to pair two video cards to increase your FPS.

[Patrick Kerbivan]

I can confirm that KSP doesn't use SLI; when I look at my video cards' load monitor while running KSP there's only load on one card. This is while using the optimized profile for KSP as applied by the NVIDIA GeForce Experience application. Someone with a bit more advanced knowledge might know of some trick for forcing SLI, but I agree with KrazyKrl that KSP's performance is generally going to be limited by your CPU performance rather than your video card.

[Morashtak]

Someone with a bit more advanced knowledge might know of some trick for forcing SLI...

The trick is to use FAFR2.

First start by using the "3D Settings" drop down menu and turn on "Show SLI Visual Indicator". Then fire up KSP and confirm that the indicator shows no hint of SLI usage (it shouldn't with typical settings).

Then in your NVIDIA Control panel go to "Manage 3D Settings", select KSP as the program to customize and try the following changes to force SLI;

• Feature....................................Settings
  
• Multi-display/mixed-GPU acceleration.......Multi display performance mode (choose this even if you only have one monitor)
  
• SLI rendering mode.........................Force alternate frame rendering 2
  
• Threaded optimization......................On

Fire up KSP and check that the SLI indicator is showing some SLI usage (it won't show much at all, sometimes virtually none which confirms it is advisable to upgrade your CPU vs your GPU for better performance). Turn off the SLI indicator and stop/start KSP to stop showing the indicator in game.

BTW, the FPS increase is just about negligible on my rig tho' your mileage may vary.

Hope this helps.

Edited August 9, 2015 by Morashtak
"It passed the spell check"

[pincushionman]

As others have said: FPS effect meager at best. Also, this would be a Unity feature, not KSP in particular.

[steve_v]

Better idea: use second GPU as dedicated PhysX processor.

Oh, wait, KSP can't use GPU accelerated PhysX. What a shame.

I guess we're stuck with lousy performance and that second GPU will just sit there twiddling its thumbs while your CPU melts.

KSP, please utilise available hardware properly. I am tired of awful performance on high-end machines.

[Canberra Gaming]

Hopefully when KSP moves to Unity 5 (1.1 I've been hearing? needs clarification) it will fix a lot of the hardware problems. I'm on a decently high end machine and I'm still hitting a lag wall at about 300ish parts. My Specs are AMD Athlon X4 860K, GTX 960 4GB, and 8GB of RAM but I feel the pain. Again hopefully Unity 5 fixes these lag walls.

[steve_v]

Meh. As I understand it, U5 implements PhysX 3.3... which supports GPU acceleration for Nvidia cards on Windows. But it's only used for cloth simulation, which is no good to us anyway.

Performance across the board should improve, but it looks like it's still unable to utilise more than one thread for a group of connected rigidbodies... which means one thread per craft. Which means performance will still suck, but maybe not quite so hard.

There are cross-platform GPU accelerated physics engines available (bullet springs to mind) but someone appears to be intent on using only stock Unity functionality.

Personally, I'm not expecting any huge performance boost. But we shall see.