Re: 65C816 adapter for 6502 computers (aka Apple II)

[mjmahon@aol.com (Michael J. Mahon)]

M. Pender wrote:

>On 3/10/04 6:21 PM, in article WpN3c.135$i76.3008@attbi_s03, "Vince Briel"
><vbrielnospamme@comcast.net> wrote:
>
>> Daryl Rictor has come up with a low profile 65816 to 6502 adapter that
>> should work on the Apple II series computers. These boards are not tested
>> but other people have done tests to get the idea working. The board is
>about
>> the same size as the 6502 so there are no worries about space requirements.
>> Check his website for more details. Also the 6502.org thread about this
>> project. Imagine running a 65816 on a II+ or IIe! Volunteers are needed so
>> check it out.
>> 
>> Daryl's web site information on this:
>> http://65c02.tripod.com/conv.html
>> 
>> 
>> 6502.org discussion thread:
>>
>http://www.6502.org/forum/viewtopic.php?t=186&postdays=0&postorder=asc&start
>> =0
>> 
>> 
>> What do you guys think?
>
>I'm not clear on the goal of the project.  If the goal is to run IIgs
>software on a IIc/e then replacing the 8-bit 6502 with a 16-bit 65816 won't
>accomplish that.  

Right--that isn't the goal.

>If the goal is to enable the IIc/e to use the broader instruction set
>available to the 65816, then its much easier to install a 65c802 in place of
>the 65c02.  I used to do that with my Laser 128--there are even macro files
>for Merlin and the Macrosparc assembler floating around (Asimov?) that I
>wrote to allow access to the broader instruction set.

That _is_ the goal, and the problem to be solved is that the 65802
is made of unobtanium.  I would guess that the 65816 is about 1000
times easier to get than the 65802.  (If I'm wrong, please let me know
and mark me down for a couple of 65802's  ;-).

>Note also that the timing of the 6502 is slightly different than the
>65c02/65c802/65816.  Thus, the 65c02 is not a drop-in replacement for the
>6502 on the Apple II or II+ -- IIRC it has something to do with the RDY
>line.

Very interesting.  I've recently encountered my first card that relies
on the RDY line for synchronization, so I'm quite curious about the
details on this (now diving into manuals...).

-michael

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