How to hack cheat codes into your Sonic CD ISO

Version 0.6    July 30, 2004

UPDATE: Changed doc so that it applies to the full USA
version of Sonic CD (instead of only 510 Beta version)
and a few other tid bits.


This original document was written by:

Tony Hedstrom    t_hedstrom@yahoo.com

www.angelfire.com/games2/codehut


This tutorial will explain how to hack your Sonic CD
game (ISO) so that you will have cheats like: "Don't
lose rings when hit" and "Mega jump" permanently hacked
into your game.  I will add more cheats if I get enough
feed back.

The method described below will only work if you are
playing Sonic CD on a computer (with an emulator) and
have your Sonic CD ISO on your hard drive.  It won't
work if you're Sonic CD ISO is on a disc (CD).

Also note that I have only tried this method on the
full Sonic CD USA version ISO, and it worked perfectly.
It may or may not work on other versions.  If you have
the Sonic CD 510 Beta ISO, see the note at the end of
this tutorial.

Also, the hacks listed below only work on the first few
levels (Palm Tree Panic), but you should be able to get
the hacks to work on the rest of the game by choosing
"continue" at the title screen.

You can get Sega CD emulators from: zophar.net

The Sonic CD ISO (game) can be a little hard to find
because the sites that have them usually don't last very
long.  I suggest using your favorite search engine
(google, etc).  If you still can't find it, try going
to the message boards at places like GSCentral.com and
asking people there, that's how I found mine. 


You'll need to know how to edit with a hex editor to
use this doc, so if you've never used a hex editor
before, I recommend using the "Help" file that comes
with most hex editors.  Editing with a hex editor is
fairly simple, so there shouldn't be any problems.


One thing I need to stress before we begin... Make sure
that you make a backup copy of your game (ISO) before
you make any changes to it, just incase anything goes
wrong.


OK, lets get to the fun part of this doc... Hacking!


"Don't lose rings when hit" hack....

We'll start off with hacking your ISO so that you won't
lose any rings when you're hit.  Open your Sonic CD ISO
with a hex editor (I use Hex Workshop, get a free trial
version from bpsoft.com).  Once you're in the hex 
editor, click on "Edit / Find".  When the "Find" window
opens, make sure that "Hex" is checked under "Value",
and that "Down" is checked under "Direction".  Where is
says "Find What", type in 33FC000000FF1512, then click
on "Find Next".  When it finds the 1st match, use your
keyboard and change the 33FC to 6006.  So the string you
just searched for should now look like this:
6006000000FF1512.

Save the changes and close the hex editor.  Open the
hacked ISO file with your favorite Sega CD emulator and
see if the hack works.

If you're curious, here's what we just did... 

33FC000000FF1512 is M68K assembly language (that's the
computer language that the Sega CD system understands).
Here's what 33FC000000FF1512 does...  If Sonic gets hit,
"33FC" tells the game to move "0000" to this RAM
address: "00FF1512".  00FF1512 is the RAM address for
how many rings you have.  Obviously, if 0000 is moved
into your ring RAM address, then you will have 0000
rings.  When we changed the 33FC to 6006, we told the
game to branch, or skip over that part, so now the game
won't put 0000 into your ring RAM address.

Remember, the above hack only works on the first few
levels, or if you continue a game.  I may add
instructions on how to get it to work on the whole
game in a future update.

Here's another interesting way we can change the
programming above so that Sonic's ring count goes to 99
when ever he's hit.  Instead of changing the 33FC to
6006, change the 0000 to 0063.  So your string would
look like this after you change it: 33FC006300FF1512.
Save your changes, exit the hex editor, fire up your
emulator, and see if your hack works.

What this does, is it tells the game that if Sonic gets
hit, move "0063" to your ring count RAM address.  If you
know anything about hex, then you know that 63 in hex =
99 in decimal.  If you want, you can change the "0000"
to any number you want from 0001 to 00FF, and you'll
get that many rings (from 1 to 255) anytime you're hit.


"Mega Jump" hack....

Now lets see how to hack you Sonic CD game so that Sonic
has mega jump.  Open up your Sonic CD ISO file with a
hex editor.  Click on "Edit / Find".  When the "Find"
window opens, make sure that "Hex" is checked under
"Value", and that "Down" is checked under "Direction".
Where is says "Find What", type in 06680038, then click
on "Find Next".  When it finds the 1st match, use your
mouse and click on the 38, then use your keyboard and
change the 38 to 18.  So the string you just searched
for should now look like this after the changes:
06680018.

Save your changes, exit the hex editor and fire up your
emulator to see if the hack worked.  Sonic should now
jump MUCH higher than normal.  If you want, you can
change the "38" part from above to other values besides
18 to get Sonic to jump higher or lower.  The lower the
number, the higher Sonic will jump.


Well, I hope your hacking was successful.  If I get
enough feed back on this doc, I'll add more cheat hacks
in the future.  Remember, I've only tried these hacks
on the full Sonic CD USA version of the game, so I don't
know if they'll work on other versions.  If the hacks
don't work for you, please email me with all the details
(which version you have, etc).

I may add instructions on how to get the hacks to work
on the entire game in a future update.  If you're the
adventurous type, you can try changing every occurrence
of the hex strings mentioned above.  That may do the 
trick.


NOTE:
If you have the Sonic CD 510 Beta ISO, use this string
when doing the "Don't lose rings when hit" hack:
33FC000000FF1220.  The "Mega Jump" hack works the same
for the Beta or the full USA version.


For the record, I used Gens V2.10 emulator, and Hex
workshop ver 2.54.


Tony Hedstrom    t_hedstrom@yahoo.com

Visit my web site for more hacking tutorials, and lots
of home made Game Genie codes...

www.angelfire.com/games2/codehut