B3 is listed as "RSVD" (Reserved), why does it need to be plugged into the +12v line?
"Pin B3 is defined as "reserved" in the PCIe specs I have access to. But my PCIe extenders have B3 wired to the other 12V lines, so I presume that more recent versions of the PCIe spec re-assigned B3 to carry the 12V voltage".
http://blog.zorinaq.com/?e=44(I am the person who introduced powered PCIe extenders to the community.)