Slot settings on a ROM 3

[Pim Blokland <nipp@nipp.nl>]

There has been much discussion in this newsgroup about the slot settings 
on IIgsses. Like that on a ROM 3, you can set slot 4 to "Your card" and 
still be able to use the mouse, while on a ROM 01, you can't.

But I'm still a bit in the dark about how this all works. Not to say 
flabbergasted.
For instance, I noticed the other day that after I set slot 3 to "Your 
card" instead of "Built in text", I can execute the APPLESOFT command 
PR#3, and the machine switches to 80 columns. But I cannot execute the 
PRODOS command PR#3; this results in a "No device connected" error.
Why?
And then all the comm software being able to use the serial port, even 
is the slot is set to "Your card". For this software it does not matter 
if the computer is a ROM 01 or a ROM 3? So, what is the difference 
between a ROM 01 and a ROM 3 then?

Can anybody tell me about this? Or direct me to a source which explains 
it all this? And explains what the difference is between a ROM 01 and a 
ROM 3?
For instance, under what circumstances should a program check if it runs 
on a 01 and what measures should it take if it finds that it does? Or on 
a 3?
Or, what use is having a switchable "modem port/your card" setting if 
the software can work with the modem port even if the setting is "your 
card"? Wouldn't it be simpler to the user if the switch simply wasn't 
there, and the machine was always set to "your card".

Just a few questions.
One warning however: I AM NOT NEW TO THE APPLE IIGS.
-- 
Groetjes, Pim

Oh, just one bit of advice you might be able to use: seventeen.
I'll be downstairs if you need me.
I'll still be downstairs if you think you don't need me.