Xircom realport in 8.1-RELEASE - how do I determine proper cbb.start_memory ?

[George Sanders]

It appears that many PCMCIA network cards no longer work in FreeBSD - this is 
documented here:  http://www.freebsd.org/cgi/query-pr.cgi?pr=115623  However 
there appears to be a workaround, wherein one sets their  hw.cbb.start_memory 
value manually.  Suggested values for xircom cards are:  sysctl 
hw.cbb.start_memory=0xf4800000 sysctl hw.cbb.start_memory=0x30000000  However, 
neither of these values work for me, and I continue to get this kind of   error:  
dc1: No station address in CIS!  etc.  I am happy to use this workaround, I just 
wonder how do I determine the proper  value for this sysctl ?  My xl0 network 
interface works, and I see that its settings are:  port 0xec80-0xecff mem 
0xf8fffc00-0xf8fffc7f  How do I compute the proper sysctl setting for my xircom 
realport cards ?  (I  have two of them to insert simultaneously)  Thanks.