Multi GPU Index
The Hardware Asylum Multi-GPU index is a portable set of data we can use to determine the multi-GPU potential of any motherboard. A higher index number indicates a favorable condition for multiple graphics cards while a lower number indicates a hindrance in one of our leading indicators. Since the Index is not dependent on system architecture it can be applied to any motherboard regardless of processor or chipset generations.
Max Support: 3x
As indicated by the PCI Express layout chart there are a total of four 16x PCI Express slots on this motherboard with three of them using bandwidth earmarked for video cards. Slot one is your primary video card slot and will run at a full 16x when only a single card is installed.
The Classified K has an interesting PCI Express layout and to accomplish it EVGA has borrowed some PCI Express lanes from the Z170 chipset and assigned them to slots four, six and seven. These also get disabled when using the nearby M.2 Slots.
For best video performance you will want to populate slots one and three with video cards. If you want to run a triple card configuration, using SLI + dedicated PhysX or AMD Crossfire, you'll populate slots one, three and five. This configuration will give you ample room for dual slot coolers and still remain within the confines of the standard ATX form factor.
In most situations dual card configurations will render the best multi GPU performance and in the case of the Classified K will also maximize the PCI Express bandwidth coming from the CPU.