[stella] Cheetah cheat code support in Stella

Subject: [stella] Cheetah cheat code support in Stella
From: "B. Watson" <atari@xxxxxxxxxxxxxx>
Date: Sat, 30 Jul 2005 21:42:56 -0400
Well, since we're doing nightly builds now, we aren't really doing alpha
releases every weekend... but I'll announce this here, and we can all
pretend it's a release :)

The current Stella build has support for Bob Colbert's Cheetah cheat
codes built directly into the emulator. To use a cheat: load the game,
enter the debugger, and enter "cheetah xxxxxx" (replace xxxxxx with
the actual cheat code). You can put multiple cheat codes in one command
(just separate them with spaces).

If you don't know what I'm talking about, see:


(I didn't know about Cheetah cheats either until this morning!)

Other goodies in recent builds:

A "saverom" command, so if you patch a ROM image (with the "rom"
command), you can save the patched version.

Updated Debugger.txt documentation, including a step-by-step tutorial on
how to create your own hacked version of Battlezone with infinite lives.
(this isn't the same thing as a Cheetah cheat, either: they don't support
bankswitching, so you couldn't use Cheetah to hack Battlezone anyway).

The beginnings of a library of built-in functions for the debugger,
mostly for use with the "breakif" command.  An example: "breakif _select"
will enter the debugger whenever you press the Game Select switch (F1 in
the default keymap).  To see a full list of functions, run the debugger
"help" command and look at the "Built-in functions" section.

I don't know if I mentioned it or not, but there are also a couple of
special variables you can use with breakif, called "_scan" and "_bank".
These return the current scanline and bank number, respectively, so
you can "breakif _scan==$60" to break at scanline $60 (halfway down
the screen in NTSC), or you can "breakif { _bank==3 && pc==myLabel }"
to break when the PC hits your label, but only in bank 3.

A "save" command that saves all your current breaks, breakifs, watches,
and traps to a script file (which you can name "romname.stella" to have
it auto-load next time you start the same ROM in Stella).

As always, you can get the latest Stella Windows and Linux builds from:


As soon as I figure out how to make Mac OS X packages, there will be
nightly builds for it, too. (Fred, you know how to do this? Reply off
list if you can help...)

Have fun, and happy debugging!

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