The mining craze is doing crazy things, try fitting this one in a chassis :) Of course these mobos do not end up in one, but Colorful is releasing the C.B250A-BTC PLUS V20 motherboard, with eight PCIe x16 slots.
The LGA1151 motherboard has a unique PCB size at 485 × 195mm and was fitted wioth the Intel B250 chipset. It has one x16 connection and then 7 mechanical x16 ones running x1 (total eight PCI-Express). There is a lot of spacing for graphics cards, ergo you can use dual-slot graphics cards.
The main specifications:
Colorful releases motherboard that can hold eight dual-slot graphics cards