Asus made a crypto-mining motherboard that supports up to 20 GPUs - The Verge
Mining Machine Systems Btc IC847 8 Pcie Slot Mining Motherboard Slot-Slot Space 6.0cm &7.0cm - China 8 GPU Motherboard and 8 Pcie Slots price | Made-in-China.com
B85 8-GPU Mining Motherboard LGA 1150
Buy Wholesale China B250c Btc Pro Motherboard For Mining Support 12 Graphics Card For Btc Eth Zec Mining Intel B250c & Btc Eth Zec Mining B250 at USD 75 | Global Sources
The ASUS H370 Mining Master connects 20 GPUs to one motherboard with PCIe over USB - Edge Up