I picked up a few boards for the HP server PSUs.  I have two different versions, a Rev1 and a Rev2.  The Rev2 only has 9 x 6 pci-e and a 4 pin.  I put a voltmeter on the 4-pin and there's no voltage output, I'm sure it is mostly for sync'ng up PSUs at large mining operations.  Does anyone know how to work that 4-pin or point me to a tutorial somewhere?

http://i.imgur.com/h150mvN.jpg