MSI X99A Tomahawk 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: 5
Optimized: 2x
Max Support: 3x

Index: 3.75
Optimized: 2x
Max Supported: 3x

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 all three 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 three 16x slots all use bandwidth directly from the CPU.  This configuration changes if you are using a 28-Lane processor where slot #5 is only allocated 8x lanes. Slot #2 is the typical primary graphics card slot and will use 16x lanes of bandwidth provided you don’t populate slot #7.  Slot #5 is the second primary slot and will always have 16x lanes of bandwidth when matched with a 40-lane processor.  Overall I found the layout to be very well laid out giving you the best support for 2-way multi gpu configurations using air or watercoolers.

For best video performance you will want to populate slots #2 and #5 with video cards.  For proper triple card configurations you'll populate slots #2, #5 and #5 and is something you can do with both 40-lane and 28-lane processors.