No, Pin 20 on the 2 4pin connector should be “no connect” as stated in ATX and SSI specification. However, Supermicro power supply has taken advantage of that empty pin and use that as a fan speed control pin. Customers might have sensed 5V on the -5V pin. However, that pin is not supplying current and is just for voltage sensing purpose only.

We believe the -5V pin should not cause problems with any customer’s motherboard.