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
This motherboard will support up to four graphics cards and is optimized for dual card operation.
For best video performance you will want to populate the top most PCI Express slot with your video card and try to avoid using the secondary slot or the ones directly below the 16x as they are hardwired for 8x PCI Express lanes.
The 3000 series Threadripper comes with 48 lanes of PCI Express out of the CPU and supports the new PCI Express Gen4 speed spec. Basically this means that 8x PCI Express lanes would transfer the same amount of data as a 16x slot using Gen3. For the Multi GPU Index the inclusion of more PCI Express lanes this will give the system a boost due to there being more bandwidth available along with only 4 of the 7 slots being installed.
All four slots are using bandwidth from the CPU with the first slot, Slot 2 being the defacto standard for your primary video card.