How many pcie lanes needed per card?

[300c]

My mining boards are all x16 slots but they only have a single pcie lane to them. Early on I tried riser cards and various motherboards, it was an unpleasant experience. If you look up BTC-37 mining motherboard on ebay you can see what I am using. I am looking for a computer to test with. This will suck if each card will actually need a full x16.