We have learned that on the 12th when Nvidia launches Tri SLI, as it calls it these days, only two products will support it. You will either have to buy three 8800 Ultras or three 8800GTX cards, as anything cheaper than that simply won’t work. We were shocked to learn that even the upcoming Geforce 8800GT won't work in Tri SLI.
The answer is quite simple, you need two SLI connectors and only 8800 Ultra and GTX support that.
Nvidia probably figured out that you need two SLI connectors and you need to connect all three cards to synchronize the rendering. We wonder how you can do it with four cards but in this scenario you probably need to synchronize cards 1 and 3 and 2 and 4 or similar.
You can also forget Tri SLI on slower 8600GTS / GT or 8500 cards, as this is a high end feature only.