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Re: Are there any 65816 card schematics?

Tristan Mumford wrote:

Michael J. Mahon wrote:



Tristan Mumford wrote:


Michael J. Mahon wrote:




Tristan Mumford wrote:



Memory addressability is the main issue though. Like I said in another
post I could just make a banked memory card, but... well, I just don't
want to do it that way :)


Accessibility of additional memory is one reason for putting the '816
on an Auxiliary Memory card.  That could give the '816 a linear view of
the memory and the 65(C)02 the conventional banked view (though seeing
chunks of the memory as "stack" is probably not very handy ;-).



Once the 65816 is enabled does it actually matter what the original CPU
sees? especially if it is held in the disabled state. I think I'm
concerned about treading on the toes of the I/O in the system more than
anything else.


No, unless you'd like the 6502 to do something for you...



Well, if I felt like being pointlessly tricky I guess the card could release
its DMA nerve pinch on the 6502 and let it do things while the 65816 plays
with its memory above 64k. I can't see a real reason to do that though.
Although if I implemented that circuitry, I might as well have something
like a x8 PLL being toggled or something instead. That would be nice for
later though.


You will need to release the "nerve pinch" quite frequently to allow
the 6502 to keep its dynamic state.  In the early years, the 6502s
would only hold their state for a few cycles, and that tended to
decrease as they aged (according to Woz).

Modern 6502s and 65C02s may be different.


-brutal hack-


Seriously, why not run your large-memory apps on a IIgs and save
a lot of non-standard trouble?



A IIgs has been on my wishlist for over a decade. Every one I have found
has been over 1000km away and at least $100 more than I'm willing to pay
for one. So I use what I've got.


Wow--I think of IIgs's as $10 items--but then there's shipping.  ;-(
The IIgs is in good supply and is relatively uncollectable!



The cheapest I've found was AU$150 plus at least AU$50 shipping. Just not
worth it for me.
Typical that what I really want is usually unobtainable.


Amazing--in the US they are quite plentiful.  Maybe getting a cheap one
on eBay and surface-shipping it (months) would make it affordable?

On the other hand, perhaps you prefer designing a coprocessor!  ;-)

-michael

NadaNet networking for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."