Discussion in 'Videocards - NVIDIA GeForce Drivers Section' started by Hayden202, Apr 4, 2011.
thanks sir7 for the info
You said pretty much the same thing I did ... and included some interesting stuff I did not know before ... so thank you is in order.
However you are still inaccurate. Its true that interframe dependencies are the common cause. However the problem isnt that data gets transfered between GPUs ... when cards operate in SLi their memory contents are perfectly synced all the time (as far as i know).
The true problem is that at any given point each GPU must work on DIFFERENT frame (after all its AFR) ... that is the reason why interframe dependencies are a problem.
To explain this further let me ilustrate: when GPU1 finishes rendering frame 1, GPU2 must be already in the process of rendering frame 2, GPU1 therefore starts rendering frame 3, then when GPU2 finishes rendering of frame 2, GPU1 must be already in the process of rendering frame 3, GPU2 therefore starts with frame 4 ... and so on and so forth.
Interframe dependencies break this because GPU1 cannot start rendering frame 3 because some operation that GPU2 does while rendering the rest of frame 2 might affect rendering of frame 3.
Also there is no cat in your picture and thats why you fail ... kidding of course
Try using the following value for compatibility bits: 0x42100105. Found it on different forums and it appears to work. There are however reports of occasional flickering textures and such ...
This works ... Thanks :0) :banana:
Thank you Fallen! Ive got some flickers on certain textures but SLI is fully working now for me
Registered to report that this did NOT fix SLI for me.
Running Forceware 270.51 with my two 460's, forcing AFR2 in Shift 2 Unleashed and entering in 0x42100105 into the SLI compatibility bits using NVIDIA Inspector yields absolutely NO performance improvement over forcing a single card. Measured using FRAPS in-game.
I can see the texture flickering that's mentioned, but the frames per second are literally identical to when running a single card.
No offense, but I think it's possible those reporting that this works are imagining things. I hope I'm wrong, though.
Some other trick they're trying that maybe I'm missing out on?
EDIT: Just want to point out that you cannot rely solely on the SLI indicators in the game to report that SLI is truly working. You must rely upon that AND an in-game fps reporting tool such as FRAPS. Otherwise you are, indeed, merely imagining a performance improvement.
"0x02100005" This Scaling with SLI (with Flickers)
Sorry, I've tried that one, too. Those are basically of the list of all the SLI compatibility bits for the various NFS games over the years, and were the most obvious area to look. There's 10 total variations, none of which work (for me, anyway).
It's still the exact same problem: SLI indicator shows SLI is active, get some flickering, but exactly the same performance as with a single card.
My FPS jumping from 20 (with 1xGTX480) to over 50 with my 3xGTX480 Setup, unfortunately it Flickers.
Why even try when they have said that both SLI/CFX is bugged in the gamecode. We need a patch for SLI/Xfire to work 100% proper.
Yes but its not solution. Youre achieving 60fps with three gtx480?
You should have like 400fps lol.
Even a single gtx480 should get smooth 60fps. Im getting 80fps average without vsync on my 570, maxing out every detail.
Sorry, that's just not true. What I said before was exactly correct.
GPUs in SLI or Crossfire do NOT have the same exact data between them... SOME of the data is the same (textures, index buffers, vertex buffers are all likely to be the same between any small number of neighboring frames, unless of course you are updating the index buffer because of some CPU-side physics altering the geometry), but the rest of the data (rendertargets, depthbuffers, intermediary surfaces) have to vary between frames by definition. If the rendertargets were the same you'd get the exact same image for every frame!
These things which vary frame to frame are what are transferring between the GPUs, causing massive stalls in what should be overlapped rendering between the GPUs. In some cases the stalls can be larger than the time it would've taken a single GPU to finish the current frame and start on the next one.. in this case you get "negative scaling" where multi-GPU actually hurts your performance relative to single GPU. AMD and NVIDIA try hard to avoid this, and this is exactly why AFR is not enabled by default for all games... they have to validate it and enable it via a profile to ensure a good experience. This means they have to make sure that the things that are causing the serialization of the GPU rendering for consecutive frames (the interframe dependencies) can be eliminated via profile without introducing corruption. If they can't, then application changes are required.
Thnx, This gave me a big improvement, despite the occasional flickering.
I had about 60fps with everything maxed (1920x1080@60), now i'm looking at +/- 90fps. :flip2:
Posted this in the Shift2 pc thread, and thought to post this here as well. Making a new profile for Shift2 and changing the following values in nVidia Inspector made sli finally work for me:
[/URL] Uploaded with ImageShack.us[/IMG]
There's still the occasional flickering, but it actually works now...
Still doesn't work
I appreciate everyone's work on this issue, but it still does not work. While using the settings in the screenshot above will utilize SLI, it is still limited, as has been mentioned, by the code.
I have tried the forced SLI settings with many different compatibility bits turned on and here is what you get:
Both GPU's working, but at 40-66% utilization (use inspector monitor)
Lower framerates (use FRAPS)
Visual oddities (e.g. flickering)
In case anyone asks: yes, I did check to see if it is a CPU throttling issue. It is not.
Thanks for all who tested/posted and for the technical posts explaining the issue
First of all, i want you to excuse me for not taking part of resolving the issue, but i just want to ask you guys some questions.
I was never about to understand those of you guys who is trying to do things that are not really necessary to do just because some program shows something. Ok i understand that most of you SLI fanatics spend some amound of money to have "maximum" gaming performance, and when something like this happens you feel kinda... screwed, but what i can't understand is why you fighting to get 100+/200+ or even more fps on a game that needs no more then constant 60 to run smooth... and even if you fix somehow this issue you will still get the exact same fps when you turn on the v-sync... so whats the point? fighting for extra... i don't know... 10-20 fps that you will never see or feel, whats the difference betwean 60 and 80 fps anyway?
You don't understand. If you'd like to enable 2X or 4X or higher antialiasing, while running at 1920x1200 or similar high resolutions, with all details or as many as possible turned on, all while maintaining a nice, smooth framerate (60 happens to work great with most monitors)... then you're going to require more GPU muscle.
The most cost effective way to do that is through SLI.
If you don't have enough GPU muscle available, then you're going to have to give up on some or all of the above. Frames, detail, FSAA, something. Your framerates will start to fall below 60 and that's undesirable, especially for a semi-realistic racing game.
Now, is it possible to still have too much GPU horsepower, overkilling your targeted goal? Sure. But then, you can either upgrade to a larger screen, or even one that supports better than 60Hz, like the awesome 120Hz ones. How does one achieve 120fps consistently? I dunno, quad GTX580's I guess?
And I wanted to confirm also that the settings provided by Joohan do not work for me, either. Same exact issue.
Yes, thanks! i got most of the things.
But if you want to run triple monitor 1080p+ resolution you still won't be able to set everything on max settings because of the the GPU Vram limitations... to me, SLI/Crossfire = waste of money (personal opinion)
I have 30" 2560x1600 display and 2x480 SLI config. Enabling SLI for Shift 2 has improved the frame rate dramatically (showing 80-90% load on both cards via nvidia inspector).
The same is of course true for the other games that support SLI, worth it when you want to play in really high resolution.