7300 expansion questions

[Patrick Barron]

I opened up my 7300 a few days ago to look around inside, and now I have
a few questions:

1)  I may not have looked hard enough, but I didn't see any slots or
    empty sockets, or anything resembling anyplace to plug board-level
    expansion in.  Where do such boards go, and how do they talk to
    the main board?

2)  In this newsgroup last week, I saw some instructions on how to expand
    the memory on a 7300 to 2mb on the main board, and thought that this
    would be a good thing to do.  Of course, when I opened the machine up,
    I saw all the 64K DRAMs soldered in.  Now, I'm not at all un-handy with
    a soldering iron, but desoldering 72 chips, putting 72 new chips in
    their places, and expecting the whole thing to work later, is not my
    idea of fun.  It would probably be much easier to build my own expansion
    memory board.  So, can anyone tell me (or point me to a reference) what
    the interface specs are for 7300 expansion boards?

3)  The diagnostics floppy can tell the difference between on-board RAM
    and expansion RAM - I assume it can do this because expansion RAM is
    in a different place in physical address space.  Where does expansion
    RAM live in physical address space, and how much expansion RAM can you
    have?

--Pat.