Problem with SLI GTX 680

[jim1976]

So I took another GTX 680 (Gigabyte OC ) and I'm trying to enable SLI w/o success.
My other GTX 680 is Palit and is reference and I don't know if that plays any role.
My problem is that the system never sees both cards in Windows.
It sees each one of them in both the first and second slot but not together when bridged for SLI. I tried uninstalling and reinstalling the Nvidia drivers w/o any luck, even refreshed my Windows 8 pro copy to see if that would happen but nothing..
My system is

Etasis 850W PSU
Asus P8Z68 V-pro Gen3
i7 2600k @ 4.2
Windows 8 pro x64

Two questions come in mind.
Is there anyway that the Gigabyte OC model is not compatible with the reference GTX80?
And second are there any BIOS settings that I should be aware of?
Please help me here with other suggestions ,I'm lost and I don't know what to do. Thanks in advance.

 

[nforce4max]

Could be power related (doubtful but look at all those 18amp rails) but I think you may have to force sli with a registry hack if nothing else works. Are you using the physical bridge or just software only? Without the bridge enabling sli on some boards for some cards doesn't work at all and other times with reduced performance.

 

[jim1976]

I'm using the bridge and I put it in both ways and places with no luck.
The problem is that I cannot see both cards under device manager in the first place so a registry hack could work? And if yes where can I find this?

 

[nforce4max]

Just search around on google for sli hack but it doesn't always work. All it does is fool the nvidia drivers into thinking your board is something else and allows sli to be enabled. Done it my self on a AMD board. Also try a different bridge as that sometimes is to blame.

 

[jim1976]

Thanks bridge could be the issue but my mobo is SLI capable. So why doesn't it work?
Can someone verify that my cards are compatible for SLI?
Any more ideas?

 

[nforce4max]

They are of the same model name and have the same physical core so yes they are sli compatible. Sli is funny when one figures how it really works and how it can be hacked to allow things that were not normally possible. Before the Fermi and Kepler era one had to rely on rom hacks but now days there is another sort of hack. It is similar but it is only good for experimenting but one could force asymmetric sli between two cards of the same core but of different models such as a 460 and a 560ti. It takes time to understand how all that works but your cards are compatible so the problem is unusual.

 

[DooKey]

Check to make sure you are using the most current BIOS for your motherboard. If you don't connect the bridge does windows see both cards?

 

[jim1976]

Well I think I have made a mistake in the beginning. I said both gpus play in the second pci-e slot but none of them does. I think the second port is defective and is causing me this problem.
I have RMA the mobo.. :/
Any other ideas that I might check as a last resort solution?

 

[aigomorla]

check to see if you have an option in motherboard that allows u to set multi on each pci-e.

like for example.. u might see a 16x / 8x and a 8x / 8x

sometimes if the pci-e lanes arent at the same speed, sli wont work.

 

[jim1976]

Thanks but it was a defective mobo. I swapped it for an Asus P8Z68 Deluxe Gen3 and it recognized SLI immediately.Case closed thanks everyone for your input.