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Possible bottleneck on SLI Performance

Last response: in Graphics & Displays
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March 24, 2014 1:16:40 PM

I have two GTX 770 graphics cards (Zotac and MSI, clocked the same) an SLI bridge, latest drivers and all that good stuff. I also have an Intel i5 4670k 16gb Ballistix Sports RAM, MSI z87-g45 gaming Mobo and 750w PSU. But, I get less frames with this SLI configuration than with only one card. Is the PSU a possible issue or the fact that the cards are different brands? Any response is appreciated, thanks
March 24, 2014 1:18:37 PM

brand doesn't create problem . . PSU brand ?
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March 24, 2014 1:19:08 PM

PSU = Corsair CX750w
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March 24, 2014 1:20:16 PM

I know different brands don't matter in Crossfire as long as they are the same GPU, but I'm unsure about nVidia--I have a Visiontek 270X and an XFX 270X running in Crossfire with no problems.

Your PSU is enough to handle two 770s, unless it's going bad.

It's either the different brand thing or some sort of driver conflict, your i5 is plenty powerful to pump frames to two 770s. Did you completely uninstall the first 770 before you installed the second?
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March 24, 2014 1:22:17 PM

things are looking good as your PSU suggests but i think some configuration mistake . . perform a clean install of drivers adn settings then try and also monitor TEMPS
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March 24, 2014 1:24:29 PM

I uninstalled the driver and reinstalled the driver on both cards, but not before putting the second one in. I did it simontanusely
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March 24, 2014 1:29:59 PM

I read about my mobo, and even though it's expensive it says "Single PCIe x16 3.0, dual 8x 3.0 8x 3.0 and 8x 4x 4x 3.0"
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March 24, 2014 1:33:10 PM

DireMe said:
I read about my mobo, and even though it's expensive it says "Single PCIe x16 3.0, dual 8x 3.0 8x 3.0 and 8x 4x 4x 3.0"


Well it still shouldn't do worse with SLI on. Does this happen with a single game or all of your games?
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March 24, 2014 1:36:53 PM

Dual x8 on PCIe 3.0 is equivalent to dual x16 on PCIe 2.0 and video cards don't even fully saturate all 16 lanes of PCIe 2.0 so I wouldn't worry about that.

If you had one 770 installed before you added another you should uninstall the drivers, run display driver uninstaller to clean everything out, shut down and install the second card. Boot up and install the latest drivers.
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March 24, 2014 1:38:32 PM

What resolution are you gaming at? I had this exact same issue with two 2GB 770's. I game at 1440p. SLI has a little more memory overhead and trying to push that many pixels with only 2GB video memory caused problems in memory intensive games (most notably modded skyrim). I was getting far worse performance with sli turned on in these scenarios... Overall I got better performance out of them (in less video memory hungry games), but sometimes I just had to turn it off and run a single card. I upgraded to 4GB 770's and the problem was resolved entirely.

edit: I was using a galaxy card and a gigabyte card iirc. Never had any issues running different brands in sli.
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Best solution

March 24, 2014 2:02:00 PM

DireMe said:
I uninstalled the driver and reinstalled the driver on both cards, but not before putting the second one in. I did it simontanusely


This is likely the issue--you needed to uninstall all drivers BEFORE installing the second card and then reinstall the drivers once both cards are installed.

It may sound silly, but I'd uninstall all nvidia drivers, remove the second card, reinstall drivers for the one card, reboot, uninstall those drivers you just installed, run Display Driver Uninstaller and shutdown, install the second card and boot up, install the latest nvidia drivers.

There's probably an easier way, but that would be the most thorough.
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March 24, 2014 2:07:37 PM

I will look more into that and if it works ill give you the best answer. Thanks for the replies
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March 24, 2014 2:12:12 PM

If the driver reinstall doesn't work, have you tried running the system on each card individually? Might be a good idea, to try to eliminate the possibility of a bad card.
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March 24, 2014 2:14:00 PM

Both cards work fine, will fix all the drivers later
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March 24, 2014 2:36:30 PM

post result when done . . .
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March 24, 2014 2:52:35 PM

Yes I'm eager to know what happens
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March 26, 2014 7:59:39 AM

Okay, I have re-installed everything, taken out cards and put them in, installed again and all that stuff you wrote earlier. It is better now, but sometimes it is the same results. Like in Battlefield 4. I got 60-70 frames with one card, now sometimes 110 frames, but it varies. It is different from game to game. Thanks for all the replies though! Appreciate it
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