As a side note, everyone is recommending this to save power by limiting controllers. However, you still need to power the fans for each miner (which draw from the controller board and contribute to its power consumption), and each fan draws ~24W. BBB boards only consume 2-3W max, so the amount of power savings is really negligible.
I use this possibility for a simpler overview.
If I have purchased total of 32 antminer S7, then it only makes 16 controllers.
Now I have a double S7 only 7 pieces , because I put together only the best miners with very low HV error rate.
Five of them are at my house
After three hours in antpool
9,711.79
9,673.46
9,729.75
9,699.34
9,717.76