Today ECS has revealed its new Scalable Dual Graphics Engine technology, or SDGE. It is their attempt to bring to market a lower cost more mainstream SLI solution.
EDGE will support up to 4 displays, and will allow for a mix of graphics interfaces. You could mix PCI Express 16X and AGP, or AGP and integrated graphics, or PCI Express and integrated graphics. You can also mix various PCI Express speeds like 16X and 4X. We are working on getting more information on this technology and will update as we have it. Below is a slide of an implementation of the technology for Intel. More details can be read at AMDZone.