From: Jim Brain (brain_at_jbrain.com)
Date: 2007-12-17 22:49:24
David Wood wrote:
> Sounds interesting no doubt. If youre using more than 64k RAM, would you
> consider using a 65816 for linear access to the memory? I'm not trying to
> turn the project into a super-computer with 16M ram. Rather, I'm attempting
> to simplify buffering/ram access programming.
>
Wow, *WAY* ahead of me. I just pulled the parts onto a board, and made
sure they would all physically fit on there. No design as yet :-) Sorry
to burst the bubble.
> Re-reading your reply, it would seem that the 6522 could easily be used to
> control bank addressing with a 16k window if all of its lines are dedicated
> to the bank address. This eliminates lines for the IEC bus though. Quite
> the challenge.
>
Yeah, I pulled the '22 into the design simply for compatibility with SW
expecting to see a '22 there. There are far better parts for banking.
> Got a preview for the board's schematic someplace? :)
>
As noted, sorry, you're way ahead of me. If you'd like to fire up EAGLE
and start, I'm happy to work with you on it.
Thinking out loud:
* Check out the 134 with on-board IO and such. It's not much more
expensive that an 02.
* I like your idea of a 816 design, but I don't know if such a
design would hurt compatibility. I assume it would not any more
than using IDE, but it's a deviation.
* I was going to suggest the C265S as the be all solution, but not
at that price. I don't pay that much for an MPU, no matter how
good it is.
* Someone needs to consider the amount of RAM in a design like this
At some point, you need more more DOS buffers (16 or so is plenty,
I think), and some scratchpad area for IDE writes. That's a bout
5kB. What else would be needed?
* ROM needed. Should a drive contain a static large ROM/FLASH for
the DOS, or should it contain a small minimal one and load a bunch
of RAM with the real DOS and then protect the RAM? I tend to like
the latter, but dunno.
Jim
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