Re: Patching the ProDOS Disk ][ driver?

[ferdimh@gmx.de]

>Boot ProDOS + BASIC.SYSTEM.
>BLOAD PRODOS,A$2000,TSYS
>Now you can edit the code in RAM.
>BSAVE PRODOS,A$2000,TSYS
ARRRGH!
How could I forget! Thank you.
But later I wrote a small program to copy $D000-$FFFF to $2000-$4FFFF
since the code in the PRODOS file is in the wrong order and
partially(!) relocated making it very difficult to understand.
> It shouldn't be so hard to do 512.
>
> Are you supposed to be able to write half tracks?  I always thought
> that the half track copy protection worked by not using the neighboring
> tracks.
>
> -- glen
I am VERY sure since I developed my circuit that it will first swap
the heads then writing halftracks. So I can either write 2 volumes of
80 (full-)tracks or one volume of 160 halftracks.

I first patched out the whole sector number checking code. Then I used
a disk I already formatted with DOS 3.3, reformatted it now having a
ProDOS File System on it. Then I patched it to 640 blocks using ZAP.
The resulting disk works! The filer prints a wrong used blocks count,
as it assumes a 280-block drive. The CAT command works okay. I also
successfully stored ~300KB of data on the disk, so the scheme works.
But now the sever problem arises: I want to write halftracks but keep
compatible to fulltracks. So I need a autodetection algorithm which I
already patched into DOS RWTS, so I'll have to patch it into the
existing ProDOS driver or write a new one (shouldn't be too difficult,
as I now hav a disassembly of the old).

BTW: I'm using ProDOS 2.0.3 and the patch was still at the correct
location.