8 cards is a major speedbump in multiple GPU systems.   Usually requires driver/bios mods.


They are giving good info.   I suggest you read others' threads on multiple GPU systems.   Theres LOTS of good info and things to learn just by going through what they did first.

Also,
They also make connectors that link the motherboard power cables so they power on at the same time.   Its smart to have identical power supplies so they turn on at the same time or problems arise.