Re: Are there any 65816 card schematics?

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

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.

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.



> 
>> -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.

> 
> 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.


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