48K banked memory

[robc638@startmail.ca (Robert C.)]

Answering Rob Jones' question, "A Solid-State Drive for the ][+" (see
question somewhere on this Board), I got thinking about a way of
bank-switching 48K blocks on the Apple 2 plus.

My idea is to make banks of memory that would duplicate the main
memory and switch it as necessary. Since the board could reside in
slot 0, I would need to write a short ML subroutine that would poke
the bank number into a slot specific address for slot 0. Logic would
then intercept the address for main memory and redirect it to the
selected 48K bank. This short program would need to be stored in a
small ROM on the Ram Card.

Looking closely at a 16K Microsoft RamCard that I have, I notice that
it has no Prom. Exactly, how does the Apple know when to switch
between the ROMs and the 12K+4K on the board?

I can handle the hardware portion fairly easily, but I would need some
help from advanced programmers to write the ML subroutine.

Thank-You
Robert.