I remember buying a bunch of delta fans to add fans to our S7-LN machines and to get them to read we had to swap the two data wires so the s7 could read them
Ah ha! That explains the Delta datasheet I just looked at for their newest fans. Their wiring diagram showed yellow as the PWM command and blue as feedback which is the reverse of most fan wire colors....
Thought they may have screwed up the diag or I was going nuts...
The other possible 'gotcha' is that there are 2 styles of PWM control and of course they are also the reverse of each other: 1 uses zero or very low pulse duty-cycle = full speed and as duty-cycle increases the fan slows down. This is safest because if the command wire is cut or shorts the fan runs a full speed. The other control method is 100% duty-cycle = 100% speed. Anyone ever check to see which Bitmain uses?