ASUS ROG Maximus X Formula Motherboard Review

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.

Index: 3
Optimized: 2x
Max Support: 2x

NVidia SLI
AMD Crossfire

As indicated by the PCI Express layout chart there are a total of three 16x PCI Express slots on this motherboard with two of them using bandwidth earmarked for video cards.  Slot two will be the primary video card slot and will run at a full 16x when only a single card is installed. 

For best video performance you will want to populate slots two and five with video cards.  Despite slot seven supporting full sized video cards it is only wired for one lane of PCI Express bandwidth AND it is coming from the PCH (Southbridge) which is not ideal for anything graphics related. 

In theory you could run a triple card configuration, using SLI + dedicated PhysX or 3-way Crossfire by populating slots two, five and seven. In most situations dual card configurations will render the best multi GPU performance maximize the PCI Express bandwidth coming from the CPU.