Technically, what is "SLI Ready"?

[Bigrustydad]

I'm trying to neck down the specifics as to what a MoBo manufacturer needs to do in order to design an SLI Ready motherboard. Why, for instance, Can't I use an SLI bridge across a pair of GTX 770s on a supermicro X9DRG-QF motherboard (LGA 2011, E5-2600 V1 or V2, C602 chipset - plenty of space between PCIex16 sockets, plenty of power, plenty of cooling - but NOT "SLI Ready" - why not? What's missing?)

By way of example, the ASUS Z9PE-D8 WS also contains the LGA-2011 socket and C602 chipset - and supports SLI and Crossfire. So, really, what is the secret ingredient that makes 1 MoBo SLI ready, and another, not?

 

[kanewolf]

On an E5-2xxx motherboard, I wonder if the PCIe lanes coming from different CPU sockets has anything to do with it?

 

[cyberkeeper1]

Scalable Link Interface. SLi is only for nvidia, and AMD / ATI has crossfire. Same idea, but it is in fact different technology, and the connection type is different.

 

[JUICEhunter]

Does the mobo have two 16x pci-e lanes? I know they won't allow any boards that don't have that spec, which is why there are a lot of crossfire mobos that aren't SLI certified.