Well I've had the same problems with two Gigabyte 560 non-Ti running in SLI as described in [Bugfix] NVIDIA GTX 560 Ti OC: Probleme mit Blackscreen, “Switch to Desktop” oder Reboot | Media Addicted. This mainly happened to me in heavy lifters like Guild Wars 2 (which seems to put even more strain at least on the VRAM than Furmark does). Testing the issue is pretty easy: leave Guild Wars 2 in the background with borderless window mode and wait until the system freezes.

In summary: when SLI is enabled, games like Guild Wars 2 crash my two 560 in either one of those styles:

  • graphics driver resets
  • frozen screen with mouse moving possible, sound still playing
  • frozen screen without mouse moving possible, sound still playing
  • black screen full freeze

Both cards could be run in non-SLI mode with GW2 and Furmark completely stable.

The exact model of my cards is: GV-N56GOC-1GI.F1 (F1 BIOS, no update available).

After fiddling around with my basic overclocking of my CPU, underclocking the 560's GPU clock and overvolting, I came to the conclusion that that didn't work for me.

Yesterday I reapplied thermal paste to both the 560, which were drowned in paste btw, to no avail (but 10C less heat). I also noticed that the WindForce cooling system didn't have any direct contact to the VRAM chips (the non-retail NVIDIA reference design of the 560 does have a cooling solution with contact to the VRAM chips).

So I downclocked the VRAM by 100 MHz (200MHz QDR, 2004 > 1900) and the system ran butterly fine. Now I've ramped the VRAM up to 1980/3960QDR instead of the original 2004/4008 MHz and its still up and running.

Before I tried all that I returned both cards back to Amazon and got two brand-new ones - which have shown the same results in SLI setup.
This may well be a generic design flaw of those 560 cards by Gigabyte - or I am a very very unlucky person.

Though looking at the problems people have with the 560 Ti with WindForce cooling from Gigabyte I doubt that pretty much.

I hope this may help some people with problems with SLI and their Gigabyte 560's.