Solaris Utility DVD found a way to enable SLI on the CrossFire-only ASUS P7P55D motherboard, you can check it out over here.
The hack in itself is simple. As some of you may already know Nvidia charges a small fee per board to enable SLI on certain series of P55 and x58 motherboards. This means that when a manufacturer gets approval to enable SLI on a series Nvidia gives them a bios string to implement so that it can be enabled by the end user. Now not all motherboard series get the certification however. It coasts $30k upfront for the series and $3 per sold board. As you can see this can get quite expensive for the company's producing the boards. Which means that some boards will not support SLI.
The easy way around this says "SU" is instead of spending an extra $70 or so dollars to get a motherboard with SLI support why not just copy the string and modify the bios of the current board? I thought it was a good question too..