RoboCop 2 (NES)

A very hard platformer that's a port of the Commodore 64 version and is also based on the movie of the same name.

Level Select#

At the title screen, press and hold Up + Right on Controller 2 and Down + Left on Controller 1 at the same time. Now, by pressing B on Controller 1, the player can cycle through levels 0 to 14. Press A to reset the level index back to 0. A sound will confirm code triggering after each time A or B is pressed. Select the "CONTINUE" option to start from the selected level.

Hidden Text#

This game shares the same music driver library that many other NES Ocean Software games used. As a result, there is a hidden version and copyright string:

MUSIC DRIVER V1.0 (C)JONATHAN DUNN & OCEAN SOFTWARE

Additionally, a small bit of placeholder text is at offset 0x01b256, at the end of BANK 6:

hello this is a bit of text

Game Genie Detection#

The game checks for the presence of a Game Genie on startup by adding each byte in $10-$26 (zeropage RAM) with a corresponding complement in PRG-ROM (located immediately after the checking routine). The routine only exits when at least one of the byte pairs produces a sum other than 0, otherwise it will loop forever and cause the game to hang.⁵

The zeropage RAM area being checked for is the setup routine executed by the Game Genie ROM just before handing over control to the game. Below is a disassembly of said routine:

$0010  LDX #$0B
$0012  LDA $90,X    ; Write Game Genie register bytes
$0014  STA $8001,X  ; for each of the 3 codes
$0017  DEX
$0018  BPL $0012    ; Loop until all bytes written
$001A  LDA $89
$001C  STA $8000    ; Set primary control byte to enter game mode
$001F  LDA #$00
$0021  STA $8000    ; Interpreted by the game's mapper, reason for write is unknown
$0024  JMP ($FFFC)  ; Jump to game's reset handler

Unfortunately, this measure can be bypassed using a single GG code by patching the first byte of the checking routine to immediately execute an RTS instruction. Use one of the below codes depending on the version:

References#