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SLI is decreasing performance?

Last response: in Graphics & Displays
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February 20, 2013 3:59:14 AM

I recently bought two PNY xlr8 performance edition 660 TI graphics cards, they both work well but when I SLI them I get less performance than if I was to only run one card... :( 

For example here is my Heaven score with 1 card: http://puu.sh/20LcY/adbed125f2, score of 2857, and here is my score with SLI: http://puu.sh/25sPC/5348bbaa18, score of 2339... Note at the bottom of each the first one actually lists my graphics card and the second picture says "Microsoft Basic Render..." Vsync is off, also.

Here is my setup

Asus M4N75TD SLI ready motherboard
AND Phenom II x6 1055T CPU
2x PNY 660 TI 2gb graphics cards in SLI...
8gb ram @ 1333mhz
750w Corsair CX750 SLI ready PSU

I believe I set it up right because when I rebooted my computer the nvidia software said that my system was SLI ready with a notification bubble and said to click it to enable it, I did here is http://puu.sh/25t9K/71e91bbc58 (this may be the problem if I have the DVI cables in the wrong spot). But I've read around saying that the monitor dvi's should be connected to the top card, which it is. I have dual monitors, so I don't know if that plays into anything...?

Please help me out, great thanks!
a c 173 U Graphics card
February 20, 2013 5:16:18 AM

for a start, you have a serious cpu bottleneck im not surprised you dont see a performance increase. But forget heaven benchmark, play a game. make sure you have the sli bridge properly installed and sli enabled in the driver, and download the latest driver.
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February 20, 2013 5:17:54 AM

No new updates are available for the nvidia software, and the SLI bridge could be a tricky question. My cards actually have two sets of gold fingers on each card, should I use the inner pair of gold fingers (the ones closer to the center of the card) or the outer pair (the ones closer to the VGA/DVI plugs? And I have played a game, my FPS is not increased at all.
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a c 173 U Graphics card
February 20, 2013 5:27:59 AM

just use one set of the "gold fingers" as you call them, doesnt matter which one, preferable the one closest to the back side of your case. If you dont use the bridge then that is why you are having problems. You also should update your motherboard bios to the latest.
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February 20, 2013 5:59:02 AM

I call them goldfingers because that's what my Asus MOBO manual refers to them as. The bridge is installed, and it's on the far fingers as it has been since the problem.

Indeed there was a BIOS update, I have done that and I do notice a slight increase in performance: http://puu.sh/25uVf/07a59700c0

But I am still at a slightly lower score than my single GPU...

Could you tell me if the problem lies here: http://puu.sh/25t9K/71e91bbc58. The image says that my monitors are hooked to GPU #2 when they're hooked to the top (upper) GPU in my case, shouldn't it be labled #1 in the nvidia software? My friend told me that it should be in #1? And why does the Heaven benchmark say that my GPU is a "Microsoft Basic Render Driver 9.18.13.597 11Mb". Shouldn't it say 660 TI or 2x 660 TI SLI? I don't know... :( 
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a c 173 U Graphics card
February 20, 2013 10:33:08 PM

i would do a full driver uninstall with Driversweeper utility, it needs to be used in windows safe mode to work properly, this will remove all traces of drivers and registry entries. also go into bios and make sure no onboard video is enabled. then reboot and reinstall the latest nvidia driver only (314.xx). It may also pay to remove the cards, and the sli bridge and re-seat them all in the slots to make sure there wasnt a bad connection somewhere.
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February 21, 2013 3:41:12 AM

I do not believe that my MOBO has any onboard video so I'll simply do the first thing you suggest right now!

Edit: Removed drivers in safe mode, and even the old ATI drivers that were left over from my previous 6850... Currently downloading all the new drivers from the nvidia website. Previously I used the CD that came with the card to install the nvidia drivers so perhaps that could have been the problem. My only issue right now is that I have to wait like 20 minutes for the 170mb download lol. I only have 3M connection speeds ;) . See you in about 20 minutes with an update!

Edit2: Swapped cards and still have no increase in performance, infact I got a bit slower performance: http://puu.sh/260Fo/3a0a44763c. Furthermore here is a graph of my card only using a max of 89% power (but like an average of 50% through the test) http://puu.sh/260DC/650d68c397.

Edit3: I OCed my CPU from stock 2.8 to 3.5 ghz and still scored lower than my original 2.8 ghz with one card, although my MAX fps was increased: http://puu.sh/262UT/e3aaf4f96d

This is frustrating... :( 
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