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: 5x
Max Supported: 4x
As indicated by the PCI Express layout chart there are a total of five 16x PCI Express slots on this motherboard with all five using bandwidth earmarked for video cards. The configuration is rather unique because you are given a choice of bandwidth allocations depending on your system configuration.
The five 16x slots all use bandwidth directly from the CPU. This configuration changes if you are using a 28-Lane processor where slot #4 is disabled completely and slot #7 loses some bandwidth. I found the overall layout to be a little strange. Slot #1 is the typical primary graphics card slot and will use 16x lanes of bandwidth provided you don’t populate slot #3. Slot #5 (which is rather far away) is the second primary slot and shares bandwidth with the upstairs neighbor (slot #4). The strangeness starts when running 3-way and 4-way SLI where you have 8x slots all the way down except for slot #5 which remains at 16x. This is due to the Slot #4 and #5 bandwidth sharing and slot #4 not being used.
For best video performance you will want to populate slots #1 and #5 with video cards. For proper quad card configurations you'll populate slots #1, #3, #5 and #7.
While researching the Multi GPU Index I successfully loaded windows with five video cards installed. These included five HD 4850's which might be rather dated in the GPU world but remains as the only 4-way capable GPU with a single slot cooler. While I consider the X99 FTW K to be optimized for dual card configurations you do have the ability to construct a five card super computer provided you use single slot coolers.