I just spent a good 2 hours looking for the same thing. I have a spare motherboard I have acquired from a friend and I did not know the manufacturer. All I could find are some numbers on it but nothing really indicating the actual model number.
I eventually found that it was a motherboard from an HP-Compaq type computer.
More digging helped me find that ASUS manufactured the motherboards for HP.
More digging finally brought me to an actual model number that eventually brought me to a user manual. whew.
I do not have the same exact motherboard but the layout is almost identical to mine except in color and the fact that my motherboard does not have SATA.
but nonetheless, I found what we are all looking for!!!!
(click image for larger size)
I cant really see a reference too much in the picture and I still have not tried to find one yet.
I think the one across from the SMI lead might be the pin that is not on the motherboard.
I found this on page 38 of this manual
http://dlcdnet.asus.com/pub/ASUS/mb/sock478/p4p800-mx/e...