SLI Compatibility Requirements

[sgtmeehaw]

I feel like this is a fairly simple question, but I just want to be sure. I want to purchase a second gtx 660ti and use sli with the one I already have. I was wondering what needed to be the same between the two cards in order for SLI to work. Is it just the chipset, or does the amount and type of RAM need to be the same two. Or the clock speed, or CUDA cores, or anything else. I just need to know to make sure the next card I will get will be compatible. The one I currently have is this,
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127696
but I can't find it being sold on the internet for a reasonable price, so any help pointing me in the right direction would be much appreciated. Thanks.

 

[battler624]

Two of the same card, same RAM, different factory overclock doesn't matter.
ASUS 670 2GB with EVGA FTW 2GB for example.

 

[rvilkman]

If they are running the same clocks and memory speeds that usually helps the combo work better and if it is the same model that usually makes it easy. But it's more about the chip than anything else.

 

[sgtmeehaw]

Thanks for the help. Both answers help just fine.