Do the cards have to be same model? I answer it with an example: You have a NVIDIA Geforce 7800GTX 256, and you want to add another card , the second card has to be 7800GTX exactly
^ ^what he said, and a good rule of thumb is that you can't mix cores(in your case G80 and G92). So your only option for SLI right now is to get another 8800GTS 640MB, though it doesn't need to be made by the same manufacturer.
I ordered two G92 8800GTSs from newegg and than cancelled. I got scared. A little less than 700$ with MIR. I saw on ebay that the old 8800GTS are selling at around 240$.
...500$ for SLI G92 ? Or should I go with 8800GT? Or should I wait for the new high end card to come in?
I never knew to cancel newegg orders. I would always just cover my eyes and pretend like I hit the "confirm order" button by accident and than say "oh well". 700$ is a lot of money though.
I would sell my old card on ebay. Sorry, not clear from the above post.
Also, if I were to buy two 8800GT should I get the 512MB or 256MB. 256 seems kinda small these days and I like to play at 1680 x 1050. It is 80$ for the difference times 2 for SLI. How can they charge 80$ for 256MB vram
Well really is your 8800GTS 640 weak ? do u have any problems in games? 8800GTS 640 is a great card still. i would change it
Remember upgrade when u really dont get the performance u need, dont just upgrade because of something new