I assume that these cards are on an SLI mainboard or something like that since I couldn't find any (old) pci versions of these cards. According to some googling I did it should be possible to enable SLI on Linux as well, because it's supported since 2005. To do that read the following manual page:http://us.download.nvidia.com/XFree86/Linux-x86/100.14.11/README/chapter-25.html
Since that probably explains it a lot better then I can (haven't got any experience with nvidia cards, nor there linux drivers).
Hope this works for you,