There are 3 standard parallel ports - 3BC, 378 and 278, as defined by the original IBM PC in 1971. (How time flies!)
Other addresses can be used, but then you will have to tell the OS about them.
On a DOS / Windows PC do a debug with d 40:0. You will see all the PAR and SER ports listed in the top line, in backwards format: 78 02 BC 03, etc.
You can do this on a LINUX box by booting up a DOS or WINDOWS floppy disk, with debug on it. Also, the CMOS startup screen after power up will usually show the ports - press PAUSE to view.
In the DOS/WIN world, if you have only one PAR port, that will be LPT1, regardless of it's address.
If you two ports, ie 378 and 278, then 378 will be LPT1 and 278 will be LPT2
If then add 3BC, it becomes 3BC=LPT1, 378=LPT2 and 278=LPT3. Note that usually ALL three ports may be set to use IRQ7.
It does not matter whether the ports are on the main board, or on seperate boards -the addresses are all that counts. Preferably use PAR cards that allow you to use jumpers to set up the ports, then no software loading will be necessary.
Charlie - if you read this, does Linux really start at the LOWER addresses, ie: 278=LPT1, 378=LPT2 and 3BC=LPT3? Just curious.
I am impressed that you gus can produce such a good product and still have time to help on these forums - thanks !
John Sadie