Re: Mystery DOS 3.3 mod.

[Rubywand <rubywand@swbell.net>]

Leslie Ayling writes ...

 ....

> Are you sure that the the DOS on the disk is indeed standard
> AppleDOS 3.3?
> 
> A quick disassembly of the area shows that these 2 pokes
> would modify the last 2 bytes of a three byte instruction.
>

     Looks like you may be off by a byte. The mod overwrites the first two
bytes of a three-byte instruction ...

B925- BC 8C C0   LDY $C0C8,X

becomes

B925- 18         CLC
B926- 60         RTS
B927- xx         xxx


The code in the routine after the RTS does not matter because the routine is
terminated.


 
> Perhaps it is a modified RWTS routine that is on the disk?
> 
 ....

     It would be a very unusual RWTS modification. Again, though, it seems that
you are just slightly misreading the code.

     This part of DOS 3.3 is not changed in any Apple version I've come across.
In the later 1980's, those writing Computist articles about "Enhanced" versions
of COPYA (which include the POKEs mentioned) did not need to be concerned about
the version of DOS 3.3 which was being patched.



Rubywand