8800GT SLI not working?

Hey, I'm new to the forums and I need some help.

I've got an older Socket 939 system that I'm trying pump a little more life in, because I'm too poor to get a real system. :( Anywho, I bought 2 x EVGA 8800GT KO's, because I thought I'd get more overall performance than a single 8800GTX, but I haven't really noticed any performance increase when it's in SLI. So, I ran 3DMark06 and found it was only faster in the Canyon Flight test; the rest of the speeds are about the same. Here's the scores that came up in Single and SLI modes in Windows Vista:

Main Test Results:
3DMark Score 8676 3DMarks in Single, 9209 3DMarks in SLI
SM 2.0 Score 3842 Marks in Single, 3846 Marks in SLI
SM 3.0 Score 4575 Marks in Single, 5334 Marks in SLI
CPU Score 1740 in Single, 1739 Marks in SLI (ZOMG! My CPU is 0.05% faster in Single Mode! LOL!)

Detailed Test Results:
Graphic Tests
1 - Return to Proxycon 31.608 in Single, 31.571 FPS in SLI
2 - Firefly Forest 32.427 in Single, 32.525 FPS in SLI

CPU Tests
CPU1 - Red Valley 0.549 in Single, 0.553 FPS in SLI
CPU2 - Red Valley 0.883 in Single, 0.875 FPS in SLI

HDR Tests
1 - Canyon Flight (SM 3.0) 50.592 in Single, 66.023 FPS in SLI
2 - Deep Freeze (SM 3.0) 40.904 in Single, 40.648 FPS in SLI

My specs are:

CPU: AMD Athlon 64 X2 4800+ Socket 939
Motherboard: Gigabyte K8N-SLI w/ nForce4 SLI MCP chipset
RAM: 4 GB of DDR400 RAM in Dual Channel Mode (1 GB Kingston, 1 GB Corsair, 2 GB Transcend)
Hard Drives: 1 x Samsung 160GB IDE (with XP on it) and 2 x Seagate 500GB SATA2 in striped RAID (with Vista on it)
DVD: LG 16x DVD Burner
Video Cards: 2 x EVGA GeForce 8800GT 512 MB in SLI mode
TV Tuner: Asus MyCinema P7131
Sound Card: Creative Sound Blaster Audigy 2 ZS Gamer
OS: Windows XP Professional 32-bit (on 160GB) and Windows Vista Ultimate 32-bit (on 2 x 500GB)
Power Supply: Enermax EG495P-VE SFMA 485Watt

Also, just to note, I couldn't find the SLI connector that came with my motherboard, so I used one from an Asus motherboard that my brother's not using; would that make a difference? Other than that, any ideas why I don't really have any performance boost in SLI?

EDIT: I should add that the test results are about the same in XP and no matter which video card I use for single mode and no matter which order of cards I use for SLI mode. When in SLI, I do have SLI enabled in the Nvidia Control Panel and I do have SLI enabled on the motherboard itself. I've used Nvidia driver versions 169.02, 169.03, and 169.09 all with the same results and I also got all the Vista hotfixes under:

I think that covers all the obvious stuff. :/ Anything else I missed?
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  1. My guess would be PSU. My old 939 system with 2ea 7800gtx in sli scored about the same.
  2. I have seen a lot of articles, including some on Tom's that say you only really get a performance gain on higher resolutions. Ill see if i can tell any difference with my dual 7900gt's on my 1920x1200 screen.
  3. Your powersupply is going to pop.
  4. just ran a quick check on 3dmark 05, settings at 1920x1200 AA at 4 samples, filtering at anisotropic, i got 5610 marks with sli and 3282 with out.
  5. itotallybelieveyou said:
    Your powersupply is going to pop.

    How? From EVGA's site, http://www.evga.com/products/moreinfo.asp?pn=512-P3-N805-A1&family=19 It specifically says, "Minimum 450 Watt for SLI mode system. (Minimum recommended power supply with +12 Volt current rating of 24 Amp.)" My power supply easily covers that. Besides, I've tried a different power supply and even plugging the video cards power connectors into a seperate power supply from the rest of the computer and still no difference.

    Anonymous said:
    I have seen a lot of articles, including some on Tom's that say you only really get a performance gain on higher resolutions. Ill see if i can tell any difference with my dual 7900gt's on my 1920x1200 screen.

    Unfortunately, I've only got the free version of 3DMark06, so I can't try higher resolutions. It's stuck at 1280x1024. :( But I was going by the VGA charts for 3DMark06 at 1280x1024 for single mode, http://www23.tomshardware.com/graphics_2007.html?modelx=33&model1=859&model2=722&chart=310 and SLI mode, http://www23.tomshardware.com/graphics_sli2007.html?modelx=33&model1=867&model2=819&chart=370 They don't have the 8800GT on the lists yet, but if you follow the closest ones (GTS or GTX, take your pick), I should be seeing at least a 50% speed increase. Besides, I've tried COD4 and Oblivion at 2048x1536 with max settings and I don't see any difference myself. I don't know about COD4, but Oblivion benchmarks are supposed to show an increase with SLI.

    The fact that I'm using an SLI connector from a different motherboard is still bugging me, though. Does anybody know if these things are all the same, or could that be my problem?
  6. Go into 3dMark06 and see if it says if you have Cooperative Display Adapters... (I think that is how they put it not sure and I just reformatted so I don't have 3dmark back on my system) it should say true or false. And just to make 100% sure you flipped the SLI switch card on the MB correct? And well it looks like an SLI bridge is not just an SLI bridge lol... Looking at the picture on this page and from what they say it looks like the bridge for this MB has printed on it which way to install such as SLI1, SLI2. Hmm that could be your problem....


    that link shows a close up of the bridge for that MB. That is weird because I have seen tons of people use different SLI bridges and be fine but then again it could be something just for your MB. Not completely sure about that. Also do you have the latest BIOS for that board? Also do you get the same results running the bench in XP as you do Vista?
  7. Yes, yes, and yes. LOL! The answer to all your questions is yes, fate0n3, but I can't seem to find where it says I have "Cooperative Display Adapters." Remember I only have the free version of 3DMark06, so it might not be in there. I dunno. Right now, I'm trying to reproduce a problem that just came up. I had some weird problem in a game of Warcraft 3 that said something like, "Machine Check Exception" in a blue screen. I never saw that before on my old card, so hopefully I don't have an SLI lemon. And I really hope I don't need the right SLI connector; I still don't know where the heck it could be!
  8. Well, that was short-lived. Thanks for your help, guys, but it looks like my second PCI-Express slot just died. I was starting to get a whole bunch of weird, random, intermittent crashes, and then suddenly, everything was working perfectly again, except "SLI mode" was gone. Windows now only detects one of the 8800GT's.

    So, I opened up the computer, took out the first video card and tried to boot off only the second video card slot. A bunch of beeps and nothing coming up on the screen. It makes the same beeps when there's no cards plugged in at all. I tried the other card and even my old 7900GT in that second PCI-E slot and nothing works. I can try all of them in the first slot; they all work fine and no more crashes either.

    I'm guessing I just found my problem: that my motherboard was probably too old and probably had a bad second PCI-E slot to begin with. Oh well. When I've got the money, I'll probably upgrade this thing to whatever new AMD quad-core and motherboard with PCI Express 2.0 in SLI that they're supposed to come out with soon. The nForce 780a chipset, I guess? And I'm not going Gigabyte, this time. I think I'll go EVGA, since they've got lifetime warranties on their boards.
  9. would u think it could be that its running SLI in 8x8x mode instead of 16x16?
  10. I don't think so. I'm not really sure, but even when they first came out with SLI back in the GeForce 6800 days, they saw some incredible performance and that was 8x8 mode back then. 16x16 mode is a rather recent concept, a year old I think, and it's still exclusive to higher-priced motherboards ($180-$250 at least), so not everyone's running SLI in 8x8 mode today, so they must be getting some performance increase.

    It could be that my motherboard is too old. The 8800GT was made for PCI-Express 2.0 and my motherboard is only 1.0a. But I still think it was my second PCI-Express slot. I almost wish it was still working so I could try some benchmarks on it to see how slow it must have been going to have my SLI to make no difference. On the other hand, I'm kind of glad it happened, because now I know exactly what's wrong with it, which is a lot more than what most other people get with these sort of problems.
  11. I am having the same problem with SLI and 8800 Gt cards. I have a MSI P6N Plat Motherboard and when i installed my second video card and connected the bridge i got the "SLI is available" message and went into the NVIDIA control panel and turned it on. However when i run the 3DMark 5 & 6 is shows false for linked adapters.

    so far i made sure the chip was flipped on MBD for SLI enabled 8X8, made sure drivers were installed properly for both cards.

    Even went so far as to remove the drivers from add/remove, go to safe mode, run driver cleaner pro, reboot reinstall.

    Also removed drivers like above and reinstalled the cards 1 at a time. The second card never requires a driver install and i never get a found new hardware message, it just auto places it in the device manager.

    Nothing in the bios for this MBD to enable SLI, only the big chip between the ports.

    The marks are the same for 3dmark and also when i load fps games, no increase.

    Any ideas?

    I am running XP pro and both video cards are BFG 8800GT cards.

    I also have a 850 power supply.

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