9 GPUs Asus Z270-A, Z270-AR
9 GPUs on a Z270-AR? How??
Just took this from their website
Expansion Slots
1 x PCIe 3.0/2.0 x16 (x16 or dual x8)
1 x PCIe 3.0/2.0 x16 (max at x4 mode)
4 x PCIe 3.0/2.0 x1
Storage
1 x M.2 Socket 3, , with M Key, type 2242/2260/2280/22110 storage devices support (SATA mode & X4 PCIE mode)*1
1 x M.2 Socket 3, , with M Key, type 2242/2260/2280 storage devices support (PCIE mode only)*2
The PRIME Z270-AR has 7 PCI-E slots. You need to add two M.2 to PCI-E expansion adapters to get 9 cards.
https://www.asus.com/us/Motherboards/PRIME-Z270-AR/specifications/
https://www.youtube.com/watch?v=DR-FkpU2KfI