Under the Microscope: Doom, Revolution X, Earthworm Jim 2

In this edition I’ve got details about some new cheat codes for Saturn games:

• Doom: technical information about the transparent walls code.
• Revolution X: a new cheat options screen.
• Earthworm Jim 2: some new cheats, plus the missing ones for the non-American versions.

Three for the price of one! Let’s get hacking…

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Doom

I posted this new cheat code for Rage Software’s port of Doom on X recently. It got around — I didn’t expect to see it referenced in Yahoo! Finance or to read a German writeup about it.

The code was:

• Pause the game
• Enter this sequence: X, Right, B, Y, X, Right, B, Y

The walls will become semi-transparent!

Black Squirrel pointed out that this code would have made more sense as XRAY XRAY.

Here’s a video of the effect in action:

The cheat works like this: function at 0601f46e is listening for button sequences while the game is paused. The game recognizes all of the ones listed here, plus this new one:

Each cheat code sets a different bit in the array of flags 060893f0. The effects seem to be:

0000 0001: Nothing
0000 0002: All Powerful Mode
0000 0004: Map All Lines
0000 0008: Map All Things
0000 0010: Nothing
0000 0020: Warp
0000 0040: Nothing?
0000 0080: Translucent walls

The missing ones seem to be unused, but I could be wrong — tell me if you discover any effects associated with them! There is one non-cheat use of this array: 0000 0100 disables the pause screen for some reason.

There is a cheat sequence that’s not hooked up to anything. If you put it in, the game just ignores it:

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Revolution X

What’s the proper subtitle for this game? Is it Revolution X: Featuring Aerosmith? Or Revolution X: Music is the Weapon? Both are on its title screen. Either way, it’s got a secret cheat menu:

• Go to the Options screen.
• Hold down C+X and enter this sequence very quickly: Down, Down, Up, Up, Left, Right, Y.
• You’ll hear a sound effect (“How dare you?”) if you did it fast enough.
• Go to the last item and press right. It will change from Go to Main to Go to Secret!!.

The Cheat Options menu items allow you to give yourself unlimited CDs, Laserdiscs, and Superguns; let you turn on invincibility; and change your starting level.

This one took me a while to understand, but the technical details aren’t that complicated once you know what’s going on. Here’s an excerpt of Ghidra’s decompilation of the function at 0604e9bc that’s counting how many of the code buttons you’ve entered correctly:

The button sequence is stored at 060c6f74.

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Earthworm Jim 2

Cheat code sites have a bunch of codes listed for the Saturn NTSC-U version of this game (see, e.g. here and here). But the equivalent ones for the PAL and NTSC-J ones have mostly remained undocumented.

On the NTSC-U version, the function at 06021d28 listens for button presses when the game is paused. It refers to the table at 060220e0, which describes the button sequences for 15 different cheat codes. There is an equivalent table at 06022120 for the PAL version and at 0602210c for the NTSC-J version.

Here’s the full list of cheat codes for each version!

There are two new ones here, but I don’t know what they do! If you do, please enlighten me. I’m also not sure about “Instant money worms,” but that’s what ConsoleDatabase.com says.

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Outro

For lots more cheat code discoveries, see my archive here.

Which other games have codes known for one region but not others? Let me know and I’ll look at them!

This post is syndicated from Rings of Saturn, Bo’s reverse engineering blog.