Tyan release the best motherboard on the market, definetly the fastest anyway.
The Tyan Thunder K8WE is the first motheboard to support SLI and it gives a dedicated 16 lanes to each slot.
The problem comes in that the SLI bridge card was not included with any of the motherboards, even to this day. It is easy to get a SLI card anywhere, but this motherboard has to have a custom one since the slots are farther apart than all other boards.
Tyan boasts SLI on this board (which I bought and greatly enjoy) but have not even (as far as I know) manufactured one or shipped one yet.