Although you can find out what the "burned-in" address is using the MacDFT
Config CDEV, there are times when you don't have this handy.
When holding the card, port to the right and the chip set facing you, look
for the ROM card (the card on the card). Now look for the serial number of
the card. It is printed on a label two chips to the left of the ROM card
on the second row from the top. It is proceeded with S/N.
Once you have found this decimal number, convert it to hex. Now add the
result (in hex) to 5000E0000000. This will be your address.
For example:
If your card's serial number is: 1969 (with a bunch of leading zeros)
1969 base 10 = 7B1 hex
5000E0000000 + 7B1 = 5000E00007B1 <= your address.