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GTX670 SLI - am I doing something wrong?

Whitestar127

Senior member
Dec 2, 2011
397
24
81
I finally bought another 4GB Asus GTX670 card and set it up in SLI. I inserted it in the second PCI-e slot in my P8P67 Deluxe, connected power cables and connected the SLI bridge.

Booted up and all looks good. Enabled SLI in drivers (314.22). Note! I did a fresh Windows-install after bying and inserting the first 670. I did not re-install drivers after inserting the second card.

But when I started testing things were not so good. It seems there is no scaling at all, or just slightly.

Anyway, here are the test results (sorry for slow ImageShack). Unless specified, all test were run at 1920x1080 with AA off and AF @ 16x

Just Cause 2:
This is single-GPU with AA 4x. All settings are max, but SSAO, HDshadows and Water emu are off. The usage is almost at 100% and the fps 132.


This is SLI (Alternate Frame Rendering 2) with AA 4x. Almost identical performance here. No wonder, since both GPUs are used only 50%. 0.5 + 0.5 = 1 isn't it? :) I used AFR2 here, because the "nVidia recommended" setting actually produced even lower fps in SLI. AFR1 was abysmal.



Far Cry 3:
Settings are mostly at medium or high, geometry at ultra. I only have an image of SLI here, but single-GPU yields almost identical performance in this spot. At the base of the nearby antenna, when overlooking the village, I get 83 in single and 93 in SLI. So a slight increase in that one spot, but far from what I expected.


Skyrim: Yeah I know this game sometimes has negative SLI scaling, but I'm giving an image here anyway, since it follows the trend from other games. Even in one of the most demanding spots (on top of stairs at Dragonsreach) it has exacly the same fps with or without SLI. Image is of SLI. At most demanding spot in Markarth I also get about the same fps with or without SLI, around 46-50.



Crysis benchmark:
I set all settings to Gamer and ran the standard GPU benchmark of the vanilla game. Here are the results:
SLI:
Play Time: 21.79s, Average FPS: 91.76
Min FPS: 57.58 at frame 197, Max FPS: 120.45 at frame 148
Single-GPU:
Play Time: 22.29s, Average FPS: 89.73
Min FPS: 51.47 at frame 178, Max FPS: 114.76 at frame 1651

In every game I made sure that "Prefer maximum performance" was enabled and of course Single-GPU, nVidia Recommended (SLI) or AFR2, depending on what I was testing.

So does anyone have a clue what is happening here? One should almost thing that my CPU is limiting the cards, but that seems a bit strange since it's running at 4.4GHz (well maybe except Skyrim, I suppose that one is CPU limited). I have seen reviews and youtube videos where they get decent scaling with setup and settings not too far from my own.

Is it a driver issue? Should I reinstall the driver or perhaps try the new 320 driver? Or, given that I'm new to the driver control panel, are there some settings that I have missed?

Need some input here. Sorry for long post. :)

Edit: I'll have a run-through with Rivatuner or something tonight, just to check that the CPU is in fact running at 4.4GHz.

Edit2: Here is a review of 670 SLI where they even use a 2500 at stock speed it seems. So I guess any CPU limiting theory goes out the Window, at least in this game.
http://hexus.net/tech/reviews/graphics/39605-nvidia-geforce-gtx-670-sli-vs-the-beasttm/?page=6
 
Last edited:

BrightCandle

Diamond Member
Mar 15, 2007
4,763
0
76
Something isn't right, I get linear scaling with Crysis 3, it utilises SLI very well. You are using lower settings than technically you need to, there is a chance that is causing a problem and pushing it to be a CPU limitation but its too widespread so I think SLI isn't working.

Just to be clear you have gone into the NVidia control panel, you have set the SLI configuration to Maximise Performance and its come back showing you SLI is enabled. IE it looks like the below:



Which assumes both cards have all power connections, SLI bridges and such in place.

If so and that all appears well run 3D Mark and get a comparison that way, games when tested at various settings can produce differing results to those presented on review sites so start with something that has known performance points and scaling to confirm it is actually working as its meant to.
 

boxleitnerb

Platinum Member
Nov 1, 2011
2,597
1
81
Far Cry 3 can be CPU bottlenecked from about 70-80fps onwards in many places. Skyrim is also CPU bottlenecked in larger settlements as the one you tested. Just Cause 2 should work fine, though. Test the default settings for SLI.

Generally if you're unsure if SLI works properly or not, increase GPU load by using SGSSAA or higher resolutions via downsampling. If that doesn't bring GPU usage up, something is definitely wrong.
 

bystander36

Diamond Member
Apr 1, 2013
5,154
132
106
All those are showing you a CPU bottleneck. I assume you are playing on a 1080p 120hz monitor, otherwise you wouldn't be turning settings down to try and get higher FPS. Since those games are being held back by the CPU, feel free to up the settings until your FPS start to drop. Then compare.
 

guskline

Diamond Member
Apr 17, 2006
5,340
474
126
Re-install the video drivers. Nvidia is pretty good about recognizing the second card but I would do a "custom" reinstall. First disable sli. Second, be sure that you have downloaded the 314.22 drivers (hold off on the beta more later). Then uninstall ALL of the nvidia drivers. Then reinstall using the custom option. There is a check to do a clean install. Be sure to check that. Then reinstall. Then enable sli. Then reboot and run your system.

As to the beta drivers, they are not supported by some benchmarks.

After the reinstall run 3d Mark or 3D mark 11, Heaven 4.0 etc to assure you are getting the performance of sli.

Note that I have 2 EVGA GTX670 FTWs in SLI in rig 1 below running a 3770k @4.4 Ghz so our scores should be close for benchmarks. You have 4Gig vram cards and mine are only 2.
 

Whitestar127

Senior member
Dec 2, 2011
397
24
81
That's exactly what it looks like. I will try 3D Mark as you say. I will also try to reinstall the driver. If that fails then I'll install the new beta. Or in worst case an older driver.
Like I said; scaling in Heaven seems to be fine, but the performance in the other games are not.
 

Whitestar127

Senior member
Dec 2, 2011
397
24
81
All those are showing you a CPU bottleneck. I assume you are playing on a 1080p 120hz monitor, otherwise you wouldn't be turning settings down to try and get higher FPS. Since those games are being held back by the CPU, feel free to up the settings until your FPS start to drop. Then compare.
You are spot on with regards to why I turn settings a bit down. That's also really the only reason why I bought this second card; to get the minimum framerate up to 120, or at least over 100. If that's not possible then it's a huge bummer.
 

TakeNoPrisoners

Platinum Member
Jun 3, 2011
2,600
1
76
That's exactly what it looks like. I will try 3D Mark as you say. I will also try to reinstall the driver. If that fails then I'll install the new beta. Or in worst case an older driver.
Like I said; scaling in Heaven seems to be fine, but the performance in the other games are not.
Use lots of AA in your tests, the whole point of this is to make your tests as GPU intensive as possible.

My guess is you are CPU limited in your tests and the fact that heaven works fine confirms it.
 

Whitestar127

Senior member
Dec 2, 2011
397
24
81
Re-install the video drivers. Nvidia is pretty good about recognizing the second card but I would do a "custom" reinstall. First disable sli. Second, be sure that you have downloaded the 314.22 drivers (hold off on the beta more later). Then uninstall ALL of the nvidia drivers. Then reinstall using the custom option. There is a check to do a clean install. Be sure to check that. Then reinstall. Then enable sli. Then reboot and run your system.

As to the beta drivers, they are not supported by some benchmarks.

After the reinstall run 3d Mark or 3D mark 11, Heaven 4.0 etc to assure you are getting the performance of sli.

Note that I have 2 EVGA GTX670 FTWs in SLI in rig 1 below running a 3770k @4.4 Ghz so our scores should be close for benchmarks. You have 4Gig vram cards and mine are only 2.
Thanks, I will try that. One small thing: Should I or will I be asked to reboot after uninstalling the driver?

And if it's not to much hassle, could I ask for some benchmarks from your system in some of these games?

Thanks for helping out, everyone. :)
 

bystander36

Diamond Member
Apr 1, 2013
5,154
132
106
You are spot on with regards to why I turn settings a bit down. That's also really the only reason why I bought this second card; to get the minimum framerate up to 120, or at least over 100. If that's not possible then it's a huge bummer.
It'll be possible in some games, yet not possible in others. You could see about being more aggressive on your CPU overclock for better results.

Developers don't usually design around the idea of more than 60 FPS, so unfortunately, it is not always possible to get over 120 FPS.
 

guskline

Diamond Member
Apr 17, 2006
5,340
474
126
Thanks, I will try that. One small thing: Should I or will I be asked to reboot after uninstalling the driver?

And if it's not to much hassle, could I ask for some benchmarks from your system in some of these games?

Thanks for helping out, everyone. :)
I sent you a PM.
 

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