ALR dual Pentium Pro motherboard….HELP

I recently acquired an ALR 10175-b dual Pent Pro motherboard. Can anyone help with specs on this. I also am in need of a power supply. It has the std. ATX power plug but beside it is one that is a six pin plug (2 rows of 3 pins), what is this plug? I cannot seem to get a std ATX power supply to come on to power this board. All connections except for the power switch are clearly marked. There is only one plug left which looks like the right connector (and I thought it was) does nothing. Any helpwould be greatly appriciated.