This is really frosting my noodle and tweaking my cookies.
I bought two EVGA 560 Ti cards with the intention of running them in SLI. The nVIDIA control panel does not give me the SLI option. This is a looooong post because I have been troubleshooting this for days, so please bear with me.
When I first got the cards, I installed one and played around with it. It worked fine. I installed the second one and it worked fine. I went to enable SLI, but the option was not listed in the nVidia control panel. After I futzed around with drivers and some other things I found on the EVGA forums, I got it working. I don't remember how I did it, but I certainly didn't get 37,000 3DMarks on a single 560 Ti.
http://3dmark.com/3dmv/3605632The performance was glorious to behold. Life was grand. Then, Windows being windows, I had to reboot for something. BAM. BSoD on boot from one of the nVidia drivers. I uninstalled the drivers and cleaned the registry. No SLI after boot. No SLI since.
The cards are identical. Their serial numbers are only 51 apart, so it is likely they came from the same batch (I am assuming). They run great individually. They benchmark well and the temps hover around 65-75 under full load, depending on the top/bottom placement. I can even OC them more, another 75 beyond the factory OC (Whooooo!), but doing so is usually overkill, so this is rare.
Below, I am going to post my support exchange with EVGA, but first ...
Hardware:
My system specs when overclocked and all other components.
http://www.modsrigs.com/detail.aspx?BuildID=27698Video card model:
http://www.evga.com/products/moreInfo.asp?pn=01G-P3-1563-AR&family=GeForce%20500%20Series%20Family&sw=PSU model:
http://www.antec.com/Believe_it/product.php?id=MjQ2MQ==OS: Windows 7 Ultimate 64 (1701 SP1)
Here is what EVGA had to say:
Q: I cannot enable SLI. The option does not show up in the nvidia control panel. I had this problem when first installing the cards, but fixed it with a clean driver reinstall. A few days ago, I rebooted and went straight to a BSoD with an error concerning nvlddmkm.sys. Reinstalling the drivers again fixed this, but now I cannot get SLI to work.
Things I have done.
1. complete uninstall/reinstall of the drivers.
2. Same as above but also cleaned the registry with drive sweeper in safe mode.
3. Tried older drivers (275, 266)
4. Used Coolbits.
5. Swapped the cards in the slots.
6. SLI bridge. No SLI bridge. Upside down SLI bridge.
7. Ran both cards through fluidmark and 3dmark 11.
8. Updated motherboard chipset drivers to ones on Gigabyte's site.
9. Flashed MB BIOS to F9 (latest)
10. Removed sound card and disabled network card.
11. Uninstalled drivers for both.
12. Disabled video cards and re-enabled them
13. Set MB BIOS to factory default settings.
14. Set them to fail-safe settings.
15. Changed "init display first" settings
16. Installed one card at a time.
17. Used afterburner/precision to futz with the voltage settings
18. Tried DVI only. Tried HDMI only. Tried one monitor only on each card. Tried one monitor only on any card.
Things I have not done.
1. Abandoned all hope
2. Tossed the PC out a window (yet). Help, please?
Answer Date: 11/07/2011
A: KickKat,
At this point it sounds like we may either have an issue with the northbridge on the motherboard or perhaps the power supply. Although each card works individually, what is the +12v reading when the cards are under load? You can get this reading using a program such as HW Monitor from CPUID, please let us know the min/max values and any fluctuation you observe.
Regards,
EVGA
Question Date: 11/07/2011
Q: I ran furmark on the first GPU and the +12v never changed from 12.21v under max load. I then loaded up folding@home and ran both cards and the CPU on full blast. Again, the voltage stayed at 12.21v and never fluctuated. I ran furmark for about 10 minutes and folded for about 30. +5v stayed at 5.11, Core stayed at 1.32 and +3.3 was stable at 3.4. There were no fluctuations.
The CPU is overclocked to 4.1G and the memory is using XMP to get to 1866 (manufacturer rated speed). GPU1 hovered around 66c and GPU2 averaged 70c. MB stayed at 25c and the CPU stabilized at 70c. Hard drives idled at 36c. Core voltage for the cards is 1.037 at factory clocks. Nothing seems too stressed.
I *can* OC the RAM to 2133 and OC the GPUs to 975,1950,2106 and the system remains completely stable, but I rarely do that except when benchmarking. OCing the cards when SLI is working is complete overkill anyway. Either way, I have the fan speed curve set to keep the cards at 75c or below. No sense in blowing them up to get 110 FPS in a game instead of 100 
Answer Date: 11/08/2011
A: Hi KickKat,
The voltages are good. Please try without the system overclocked as we have seen sometimes where the system overclock can affect the cards. Also, if possible try to SLI them in another system to rule out if it is a motherboard issue.
Regards,
EVGA
Question Date: 11/08/2011
Q: Something tells me it isn't the cards. I see this problem happening way too often on the forums. Like I said, I had trouble initially, but eventually got SLI working. Regretfully, I don't remember exactly what I did, but it involved the stickied uninstall guide on the forums and, perhaps, Coolbits. I only started having trouble again when I uninstalled and reinstalled the drivers.
The info on Coolbits is a little confusing. Merging the Coolbits reg file into the registry sets the Coolbits DWord to 0xffffffff. NVidia's SLI Zone says to change it to 0x00000018. Other places suggest 0x00000003. Coolbits is old anyway and I shouldn't need it, but it's the very last thing I changed in a group of 3 or 4 changes before SLI started working.
It seems like it has to be a driver conflict/issue. SLI was working. Windows booted into a blue screen complaining about a nvidia system driver (I had installed some things, but nothing video or audio related except I removed my SoundBlaster card drivers). I uninstalled and reinstalled the video drivers and the blue screen went away. Now both cards work, only I am back to no SLI.
Answer Date: 11/09/2011
A: Hi KickKat,
It is not necessary to run Coolbits as the cards are the same model numbers as listed under your products on your account. You can get the older drivers here to try. The SLI mode will only be in the Nvidia Control Panel if everything is working correctly and for SLI. To eliminate the motherboard and the windows load if possible try to SLI the card in a different system and see if there is any change.
Regards,
EVGA
Question Date: 11/09/2011
Q: I took out one of the cards and did a clean install of the 266.66 drivers. I then put the second card back in and installed the drivers a second time to get the second card working. Still no SLI. Unfortunately, I only have one SLI capable MB. I might try booting into Linux and see what that does for me.
Answer Date: 11/10/2011
A: KickKat,
Can you please try re-flashing the cards with the latest bios? - http://www.evga.com/forums/tm.aspx?m=1034790
Question Date: 11/12/2011
Q: I flashed both cards and had no problems during the process. I rebooted and nothing had changed. I saw where nvidia had beta drivers out, so I tried them. Still no SLI option.
Answer Date: 11/12/2011
A: KickKat,
SLI is mostly software related and partially hardware(motherboard,graphics cards). Have you tried contacting Gigabyte? This could possibly be a motherboard issue with the PCI express slot or with the board initializing SLI. Considering that all your testing has mostly focused on the graphics cards, I can see that it has passed most of that testing which would tell me that the graphics cards are good. Your power supply is more than sufficient to run your set up so we can rule that out. Try contacting Gigabyte about the issue and see if they can assist in troubleshooting as it appears the graphics cards are running sufficiently. Get back to us with your results so we can further assist you.
The nVidia support forums have yielded no results and Gigabyte tech support is ... sluggish.
Oh! Last thing I tried - I installed Windows 7 on a spare HDD and loaded the nVidia drivers. Still no SLI.
I just got Skyrim and want to crank it up
Help me, giga-byte.co.uk. You're my only hope.
