[Coco] Kinda off-topic, kinda crazy question about the Liber809

[Steven Hirsch]

On Tue, 15 May 2012, James Igou wrote:

> Steven Hirsch <snhirsch at ...> writes:
>
>>
>> On Fri, 11 May 2012, Theodore (Alex) Evans wrote:
>>
>>> On 12-05-10 03:28 PM, Juan Castro wrote:
>>>> How hard would it be to make a similar daughterboard for the 65C816?
>>>> ("Liber816?") So one could do some 16-bit assembly programming and not have
>>>> to forgo the Atari machine's native software forever?
>>>
>>> This is going to sound crazy, but the 65C816 is actually pin compatible with
>>> the 6502.  From what I understand there is only a 1 pin difference between a
>>> standard 6502 and the one used in XL series 8-bit Ataris
>>
>> If that was true, every Apple 2 hobbyist in the world would have
>> back-fitted their machines.  You may want to take another look at the data
>> sheets.
>>
>> Are you possibly confusing the issue with the 65C802? That short lived
>> chip was completely pin-compatible with the 65C02 - I have a couple here
>> that were used in Apple IIe boxen.

> Actually, comparing the 65C816 to the 6502,
> they do seem to have a lot of compatible signals.
> Boisy has posted the schematics for the Liber809.
> Maybe its time to do a little research.
>
> There IS one big problem:
> Its the same one that effectively prevents a 3.58 MHz 63C09E
>> From being used in a board similar to the Liber809.
> Like the Color Computer, virtually all the clock signals in an 8 bit Atari
> Are derived by dividing a single clock. So memory, CPU, and video timing are
> All interrelated.
>
> You can't just increase the CPU speed.
>
> BTW - This swap has been done by a Commodore hacker (don't you do web searches).
> http://www.baltissen.org/newhtm/02to816.htm

I do plenty of web searches.  If there's anything that's become clear in 
15-odd years of searching, it's that some folks have a knack for finding 
exactly the right keywords and some don't.  I tend to over-think search 
terms and generally fall into the latter group.  My track-record at 
finding things is not particularly good.

The subject of processor swaps comes up repeatedly on the Apple 2 forums 
and far smarter folks than I had concluded it wasn't workable.  In 
retrospect, that may be due to the A2's requirements for video generation.

I'll mention the above page and see what folks think.

Steve


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