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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:



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.



There is another option, which is a little frivolous...

65816 and 65802 CPUs are only a little over US$7 from WDC. They sport a
fully static design.


I didn't realize that '802s were still available!


Yank the original '02, plug in an '802, and still have the '816 accelerator
board.
Although, once the 65816 card is active why would I care what happens to the
6502? Unless it goes rogue and interferes with the bus when it gets
amnesia.


Since it could do literally anything, you'd have to make sure it never
took another bus cycle, unless you forced a reset.


-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?



Perhaps. I wonder how much something that large would cost to ship. Still,
surface is pretty inexpensive.

Fun fact: International postage usually works out a lot less expensive than
national postage over here.


Ouch!


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



I'd actually like it both ways! I've always wanted a IIgs, and a processor
board for one of the 6502 based apple 2s.


Cool.

-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."