SLI troubles

After a huge cock up by aria.co.uk when returning my two 6600GTs I decided I'd use the credit they eventually gave me to buy something a little bit better and got myself two BFG 7600GT OCs to put in SLI. The problem is when I shove 'em in together with SLI enabled I get little green artifacts across the screen, however when the cards are in individually they run fine and I haven't noticed any problems with either of them.

Anyone have any idea what might be causing this? I reckon it's gotta be either the SLI bridge or the second PCIE slot, perhaps.

Also, anyone know where I can buy a replacement SLI bridge connector in the UK? They're quite tricky to find.

Thanks

How hot are the cards when in SLi configuration? Overheating can often cause artifacting. One other thing is graphics drivers. Its possible that this is a bug in the drivers. I'd consider upgrading to the latest driver version, or if you have the latest ones, rolling back.

IMHO its a power supply/current issue.

However, from the BFG-Tech Support FAQ:

Q. My display becomes distorted after installing my new BFG card, why?
A. A graphics card has a power connector, please make sure a power cable from you system power supply is plugged into it. A power supply not meeting the minimum requirements can also cause this. Please check the packaging or the product page at www.bfgtech.com <http://www.bfgtech.com/> for power supply requirements for your card.

Q. I am setting up my SLI system, should I put both BFG SLI ready cards in at once or one at a time?

A. You should check with the documentation that came with your motherboard to be certain. We suggest installing the top (closest to CPU) card first then the OS and drivers. Once the system is up and stable shut it down and switch the SLI/Single mode selector card (refer to system manual) to SLI or Dual. Insert the second card and the SLI connector across the top of the two cards. Boot the system and go into the bios to check for any SLI settings, make sure they are set to auto or SLI. After the systems boots the second card will be detected and the drivers installed and the system will need to be rebooted. Once windows loads you will see an “SLI capable system” message. Click on this message and select the “Enable SLI multi-GPU” checkbox, then “Apply” and “ok”. The system will reboot and you will see an “SLI has been enable” message. Enjoy!

Q. What is causing vertical lines and/or pixellation?

A. Please visit or check with your motherboard manufacturer for the latest BIOS and chipset drivers. If this does not fix the problem contact BFG Tech Support @ 1-866-234-3499

Hope this helps! :thumbup:

Thanks for all the help, I think I've found the problem.

I have a Turbine 550W PSU which has the following power specs:

+3.3V: 36A
+5V: 36A
+12V1: 20A
+12V2: 18A
-12V: 0.8A
+5Vsb: 2.5A
550W maximum output

After some searching I discovered on the BFG site that:
A 350W PCI Express compliant system power supply (with 12V current rating of 20A or more)
For two GeForce 7600 GT-based graphics cards running in NVIDIA SLIconfigurations, a minimum 450W system power supply (with 12V rating of 28A) is recommended.


I, foolishly, had not looked beyond simply the wattage of the power requirements, so I suppose it's not a simple case of buying a new SLI bridge, but spending another £80 on a decent PSU. :/

I suppose I'm gonna gonna have to beg my parents for another loan.

Edit: Or perhaps not... I'm confused, now. I have little experience with PSUs, so I dunno. Are 12v1 and 12v2 combined or something? I was looking at an OCZ PSU that can apparently run 7900GTX SLI, but has 4 (I believe they're called rails) of +12v all at 18A. So... I'm confused. My PSU should, then, in theory run the two cards as it would be 38A combined... If that's how it works.

Well you have two +12 volt rails, adding up to 38 amps in total. I would have thought that would have been more than enough. Those BFG 7600GTs don't even need additional power from the PSU.