Why only 4 board work?
-----
Hash rate: 1TH/s = 1000GH/s (can overclock to over 1.3TH/s = 1300GH/s)
Processor Chips: 40 * A1 28nm ASIC Chips
Modules: 5 module boards (200GH/s per board) +/- 20% tolerance.
This is SCAM