Re: G.I. Joe fix-- using a SECTOR EDITOR

[Rubywand <rubywand@swbell.net>]

kahuna_j writes ...
> 
> In article <39ACAA58.DF223027@swbell.net>,
>   Rubywand <rubywand@swbell.net> wrote:
> > thomaslai@my-deja.com writes ...
> > >
 ....
> > > I have found a file in my harddisk (it maybe download from asimov
> > > or newsgroup).  It tells how to fix this:
> > >
> > >     To get GI Joe to run, change the bytes D0 F1 to EA EA at
> > >     offset $0125 (track 0, sector 1, byte $25) of the disk image
> > >     for side 1 of the game.
> > >     Without this change, the disk will spin forever after
> > >     displaying the
> > >     cracker's title page.  This worked for AppleWin,
> > >     so perhaps it will
> > >     work for the other emulators as well.
> > >
 ....

> I could use a quick hint on how to do this.  I have tried figuring out
> the debugger on Applewin, but it's a mystery to me.
> 
 ....

     Manuel's idea (using a PC Hex editor program on the .dsk file) is a
pretty quick way to edit sectors-- each sector is 256 ($100) bytes.

     Probably the easiest way is to use the SECTOR EDITOR option in a DOS 3.3
version of Copy II Plus. (Later DOS 3.3/ProDOS versions of Copy II Plus
include the Sector Editor; but, you have to go to COPY---> BIT COPY to get to
the editor. DOS 3.3-only versions include SECTOR EDITOR in the main Utilities
menu.)

 
     A good version of DOS 3.3 Copy II Plus is included on the TNILUTIL.dsk
disk image available from Ground at ...

ftp://ground.ecn.uiowa.edu/apple2/useful.stuff/Disks/ .


     The main advantage of using the Copy II Plus SECTOR EDITOR is that it is
the editor used by most of the persons who write patches like the one
supplied by Thomas Lai. The directions to change such-n-such byte(s) in
Sector x on Track y usually fit the SECTOR EDITOR display.
     
     For example, suppose you start DOS 3.3 Copy II Plus on your emulator.
Then you swap in the GI Joe Disk1 (in Drive 1) and select "SECTOR EDITOR".
Then ...

o- You press R to Read a sector and enter "0" (press 0 followed by RETURN)
for Track and "1" for sector.

o- When Sector 1 ($01) on Track 0 ($00) is displayed, you use the I, J, K, M
keys to move to the byte at location $25 (the sixth byte on the row
designated "20").  It should have the value "D0" ($D0) and the next byte
should have the value "F1" ($F1).

o- Press H to start entering hexadecimal values.

o- Type in "EA". Press SPACE (the key you press to get to the next byte) and
type in "EA" again. Press RETURN to exit hexadecimal entry. The bytes at $25
and $26 (sixth and seventh bytes on the "20" row) should be EA EA.

o- Press W to tell SECTOR EDITOR that you want to Write the changed sector to
disk and press RETURN twice to accept the Track and Sector values. Copy II
Plus will write the changed sector and the patch is done!


     Some useful things to know about the Copy II Plus SECTOR EDITOR:

o- Pressing ? shows a Help screen describing the SECTOR EDITOR key commands.

o- When doing H (hexadecimal) entries in a sector, pressing an illegal key
(like a U) kicks you out of H entry mode. You will need to press H again to
be able to make more entries.

o- Pressing ESCape gets you back to the main Utilities screen.



Rubywand