Msg: 5115 *Conference*

06-13-94 16:32:44

From: COMET _

To : ALL

Subj: MEMORY EXPANSION

I have received a copy of the catalog of the club. There are a few
(incompatible) ways to expand memory. I understand bank-switching <my 1977
Atari Video Computer System (VCS) has several
 game program cartridges which use bank-switching> and am hoping you all would
give me some advice.
 
I want to know which system would allow the most RAM total.
 
Also, I am interested in some details of implementation: it would be nice to be
able to write programs that use more than 29638 bytes of memory.  I think that
the bank-switching is accomplished by writing values to some output port, but 
if my program gets switched out, the program counter register in the CPU will
still want to go to the next address...  how do I get the program to continue
on the next bank?  How much (if any) global area is there?  Is the only
read/write locations that are saved when banks are switched the port address
space and the registers?  How about display memory?  Is that banked, too? And
how about memory controlled by other chips, like DATE/TIME/DAY?
 
Since I am interested in programming, myself, far more than in using already
written programs, these details matter to me more than knowing what programs
are available that actually make use of these features.
 
I enjoy my Model 100, and enjoy learning about ROM routines and  machine
language programming.
 
I have a bookshelf full of books on recreational/scientific computing. I wrote
my own disassembler (of course), but hand-assemble my programs, to save space.
(I write my programs on paper, first, flowcharts and all.)
 
I look forward to hearing a technical overview comparing and contrasting the
various devices available here to expand memory.  I *will* buy!  :)