Action replay codes for nightmare difficulty in Saturn Doom


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It doesn't appear to have been found already. There was a report recently on Kronos Discord by user WhiteySnakey that the nightmare difficulty could be unlocked in the PSX version of Doom, and he thought that since the Saturn version shares some similarities with the PSX one, that difficulty level could also be hidden inside.

So I gave it a shot with Kronos Cheat search feature, and got lucky. Here are the Action replay codes to unlock the nightmare difficulty level in all 3 regions of Saturn Doom :
  • The master code is the same for the 3 regions, it's the default one on my Action replay plus :
    F6000914 C305
    B6002800 0000
  • US version cheat code :
    1604A2AA 0004
    16065626 0074
  • Japanese version cheat code :
    1604A306 0004
    16065682 0074
  • European version cheat code :
    1604A166 0004
    160654DA 0074
Enabling this cheat locks the difficulty option in nightmare mode (that's the effect of the 1st line of the code).
Here is how the main menu looks in the European version with the cheat enabled :
The name of the difficulty is displayed with a string that happens to be in memory where the "Nightmare" string should be. The 2nd line of the code serves to insert a terminal 0, instead of character "S", to interrupt the string. It makes the string to be the same length as "Ultra Violence". Without that terminal 0, the string is too long and crashes the game.
The problem is that this string is used for the password display. So each time a password contains the character "S", its display will be interrupted. However only the display is impacted. A password containing "S" can still be fully input and processed by the game.

In game, monster placement is the same as in Ultra Violence, but they move faster, shoot at a faster rate and their projectiles move faster. Contrary to the PC version, monsters don't respawn (thankfully, it's hard enough).

I don't know if the game can be completed in that mode, I've only been through 4 levels before I got toasted.

Also note that when continuing a game with a password without the cheat, the difficulty is set by the password, however a password obtained with the cheat enabled and input with the cheat disabled will set the difficulty as "I am a wimp". So a password obtained in the nightmare difficulty must be input with the cheat enabled in order to continue the game with the same difficulty, and that only works when the password is launched from the main menu. When launched from the pause menu, the difficulty is set as if the cheat was disabled (so "I am a wimp" for a password obtained in nightmare). And a password obtained in an easier difficulty can be used with the cheat enabled to continue the game in nightmare mode if launched from the main menu.

The cheat codes work in Kronos emulator without needing the master code. They should be input after the Sega logo, in Tools > Cheat Lists.

A tutorial on how to use the Cheat search in Kronos, made by @Benjamin Siskoo :

An Action replay code is obtained from the address found in Kronos Cheat search that way :
  • The 1st part of the code is the hexadecimal memory address found in Kronos for a 16 bit value, with the initial 0 of the address replaced by 1.
  • The 2nd part is the hexadecimal 16 bit value to be set at that memory address.