[Coco] any interest in an 8MB ram card for COCO3?

[John W. Linville]

On Fri, Apr 16, 2010 at 04:43:32PM -0400, Aaron Wolfe wrote:
> On Fri, Apr 16, 2010 at 4:10 PM, John W. Linville
> <linville at tuxdriver.com> wrote:
> > On Fri, Apr 16, 2010 at 02:47:28PM -0400, Stephen Adolph wrote:
> >> If Nitros-9 won't be extended to address more memory then there is no
> >> point I suppose.  The scope of what I am thinking of is a RAM card
> >> only - no software, no application...just a RAM subsystem...Steve
> >
> > There is, of course, the Disto(?) 1- and 2-meg designs that NitrOS-9
> > should support.  And there was Paul Barton's NoCan3(?) that went to
> > 8-meg as well -- I'm not sure how much support there is for that one.
> >
> > An SRAM-based card would have a different hardware design, but
> > it certainly could have a programming architecture similar (or
> > identical) to the designs mentioned above.  If you are only doing a
> > windowed-memory (a la DOS EMS memory) or RAMdisk device then I would
> > be much less intersted.
> 
> 
> Given that the 6809 has only 16 address bits, doesn't all access to
> more than 64k use a scheme much like DOS EMS memory, even in a 128k
> coco 3?

I guess that depends on your point of view. :-)  What I mean to say
is if the hardware provides 8k pages using a scheme more-or-less
compatible with the existing "MMU" (i.e. bank-switching) hardware in
the cc3 (e.g. the Disto design) that is one thing, but if for example
it provided a selectable window at a fixed address or was accessed via
a FIFO or somesuch then that is something different.  Somewhere around
here I have an expansion cartridge that uses a design more like the
latter and is therefore really only useful as a RAM disk.

Hth!

John

P.S.  The Banker design (from J&M?) is another variation, swapping
32k segments in a fashion similar to the SAM mappings.  I dunno if
NitrOS-9 can do anything more useful than a RAM disk with that either,
and in any case I would not recommend that sort of design.
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.