>Its address was 0x3bc-0x3be. The BIOS would build the LPT
>address table in RAM by first looking here for an LPT, and,
>if it found one, would call it LPT1. If not, the port at
>0x378 would be LPT1.

In actual fact the BIOS code was a bit cleverer than that. For both the
parallel and serial ports there are tables of standard addresses for the
ports. Each table had space for 4 addresses, the parallel port table
contained 3 addresses, and the serial port table 2 addresses.

The BIOS code would check the addresses in each table, and discard the
addresses where no hardware was found. The parallel port table contained
378, 278, and 3BC in that order. Any of these could be LPT1 if no hardware
was found for a prior address in the table. Hence it is also possible for
address 278 to appear as LPT1.

The second address for which hardware was found would then be labelled as
LPT2. The serial port selection did the same trick. This could create
confusion if the ports were on different cards, and the card for a lower
port number was removed, and the machine rebooted without it replaced.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.