F Fuzzball New Member Feb 9, 2014 2 0 1 Mar 12, 2014 #41 Aluminum said: The rear slot extension is for a proprietary IPMI card. I doubt you can use the rear slot with any normal card, it is most likely meant to pass non-pci signals. Click to expand... Someone has had to give that slot a shot to see if it'd work. Just a bad tease from HP if it's got a proprietary pin out. I'd love to be able to fit a third card in there with a ribbon riser.