interface order with multiple cards of same type

[Aaron Martinez]

apologies if this has been covered in the past, I searched on this and 
couldn't find anything, although i'm sure it's the wording i'm using.

My question is.  I have OBSD 4.0 running on an Asus p3b-F with 6 pci 
slots that i'm wanting to use as a router/firewall.  I have 5 fxp 
interfaces in the machine inserted starting from the bottom pci slot 
up.  When the machine boots up it finds them just fine, but I never know 
what order the cards are in.  (i.e. fxp0 was in the third  slot as 
opposed to the first or last slot populated with a card, as i would have 
expected).  Is there a way to hard code this into the hostname.fxpN 
file, as to assign the number of the interface based on the hardware 
address as opposed to the ordering of the cards in the machine?  I 
looked in the man page for hostname.if but saw no way mentioned.

A second related question, in the above example, how exactly does OBSD 
choose the interface number?  I was under the impression it used the 
slot to assign the interface number which is why i was so surprised to 
see that fxp0 the third slot, fxp2 was in the top (occupied) slot and 
fxp4 was in the bottom.   I have all of the pci slots set to auto in the 
bios if that makes any difference.

Thanks in advance.

Aaron