I have 2x geForce 8800 GTS 512mb GPUs on a nForce 780i SLI mobo. However, I have 4gb of Corsair 6400C5DHX memory. In the BIOS is tells me that this memory isn’t SLI ready. So, I have two questions:
 
First, how can you tell if SLI is running properly?  
 
Second, I’ve heard that the memory doesn’t need to be SLI ready to run it, but how do I get it to work, and is there any performance degradation by not having SLI ready memory?
 
Thanks.
Gary K.

http://www.tomshardware.co.uk/foru [...] sfire-faqs
 
WARNING: Some RAMs have SLI or CrossFire logo on them. Many people ask if they are the only RAMs which support SLI or Crossfire.  
Well thats wrong , there are many RAMs which dont have SLI or CrossFire logo but you can use SLI or CrossFire with them without any problem.

 
 And I will be happy give a second opinion suporting what Maziar is saying, I have never heard of it, there may be a performance reason similar to having matched modules or something but Im guessing its just a marketing thing.  
 If anyone knows differant please share the knowledge  
    Mactronix  

Marketing gimmick in my opinion...
Same with SLi-certified PSUs....    
I have 2 8800GTXs in SLi and 4x1Gb Corsair PC6400 C4 DHX which isn't SLi certified, and nothing has exploded yet!    

In the Nvidia control panel choose 'advanced view' at the top you should have 'file' 'edit'  'view' & '3d settings', click on 3d settings and then click 'show SLI visual indicators' this will bring up green bars on the left of the screen whenever Sli is used.