Last week AMD confirmed that in some applications, such as 3Dmark06, you can get more than a 300 percent performance boost over a single card with its HD3870 X2.
This won’t be the case in all applications all the time, but at least it is a nice show off number. In certain tests you will get a 320 percent performance increase with four cards; this looks quite promising.
The big problem is that in some games the performance boost can be as little as 20 to 30 percent. At least it would be cool to be able to boast that you have four graphics cards inside your rig.
We know it's crazy, but so is Bugatti's Veyron.