[Coco] OT:The Apple II source code for Prince Of Persia- found after 22 years

[jdaggett at gate.net]

David

6502 code is very similar to 6800 as is the architecture. A straight forward mapping of 
comparable code is a rather daunting task for all but small blocks of code. there are 
instruction that do not directly translate due to differences in the register sizes and function of 
the instruction execution. An example of that is when stacking, the 6502 pushes a byte onto 
the stack and then decrements. the 6809 decrements the pointer and then pushes a byte on 
the stack. The 6502 has a D flag in the condition code register that has no meaning in the 
6809. There are a few instructions that use the D flag and care is needed when translating 
those instructions to 6809 code. 

One warning from the author of the CSC 6502 to 6809 translator made is if porting 6502 
code to run on an OS9 system, non position independent code does not run well in OS9. The 
data structutes will in single user mode. Now that was written back in 1982 and with the mods 
that the NitrOS9 group has done that may or may not be the case. Code then was often 
written in a position dependant mannor and that could be an issue if porting to OS9. 

james
 

On 5 Jun 2012 at 16:48, David Roper wrote:

> Yep - that's me, posted a while back before the source-code release.
> I'm running on negative time at the moment, but perhaps I'll give it a
> go "one day"
> 
> Any 6502 gurus willing to lend a hand, when the time comes?
> 
> - David
> 
> On 5 June 2012 16:33, Mark McDougall <msmcdoug at iinet.net.au> wrote:
> > <http://cocogamedev.maxforum.org/2011/10/11/prince-of-persia/>
> >
> >
> > On 5/06/2012 4:20 PM, David Roper wrote:
> >> who's up for porting it to the coco 3? :)
> >>
> >> On 5 June 2012 16:10, Tony Cappellini <cappy2112 at gmail.com> wrote:
> >>> For those who like 6502 assembly language
> >>> http://jordanmechner.com/blog/2012/04/source/
> >>>
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