npk@S.CC.PURDUE.EDU ("Jobe Wan") (12/14/86)
I am expanding the RAM on my Atari 800, I've got more-or-less
complete access to the system bus, and I can deactivate everything but the
GTIA and Antic chips. I am confident that I can add memory just about
anywhere I want to, but I don't know what the conventions are for calling
banks up on the various expansion schemes. The 800XL does one thing, the
800XE does another, and the Axlon Ramdisk boards do something completely
different. The best option seems to use many banks, and a hardware (or
software) switch to determine which machine to emulate, and where the
banks and triggers should be. But I can't find the specs. Where can I find
out EXACTLY what addresses are used and such forth for the 800XL, 800XE, 130XE,
65XE, 800 with RAMDISK, etc? I'm about to etch some memory cards, and I want
to do this right the first time.
Also, the Axlon specification is, I think, that banks are selected
by storing a value from 0 to 7 (for a 128K rambank) or 0-15 (for a 256K bank)
in the top portion of $CFxx. As far as I can tell, those lines are not
available outside of the OS card, except by soldering wires, (which I did).
How is everybody doing this? I'm not out to make a profit, I am a hobbyist,
and I am hoping to donate several bare boards to my high school.
Thank you for your help
Scott Mark
npk@s.cc.purdue.edu.UUCP
.ARPA
.BITNET
P.S. I am hoping to lay these out over Christmas break, so if you could
reply by Dec. 18th, I'd appreciate it.