IBM PC printer adapter schematic

[Tony Duell]

> > Well, you can have as may printer adapters as yopu like if you can set
> > them all to different addresses and if you're writing your own software
> > to talk to them...
> 
> Naturally.  The problem I see is that only the older cards might let
> you set the printer port to respond to arbitrary addresses - the ones

That's an issue of the cards, not the system :-)

In my experience, most printer adapters only let you set 0x378 and 0x278. 
Some also allowed 0x3bc, but very few allowed other addresses.

If it's just a simple printer card (as opposed to a multi-I/O thing), or
if it's mostly discrete logic, you can use an inverter to change the state
of one of the address lines to shift it to some other address. But if 
it's a multi-I/O card with all the logic in one ASIC, doing that will 
move other I/O systems to other addresses which may well not be desirable.

I once saw an async card (I think it was Olivetti) were there was a whole 
bank of links to set the address. The instructions gave the settings for 
a few standard addresses. It was pretty obvious (confirmed by tracing out 
part of th eschematic) that the links actually defined the states of 
A3..A9, and you could set it to any address you liked

-tony