Gun & Frontier

Gun & Frontier
Also known as: Gun Frontier (JP) Developer: Taito Publisher: Taito Platform: Arcade (Taito F2 System) Released internationally: January 1991 This game has unused code. This game has unused graphics. This game has debugging material. This game has a hidden level select.

Gun & Frontier is a shooter with a strange story about a 22nd century gold rush in space. Space pirates get involved, as they so often do, and it's up to the player and possibly the player's friend to stop them.

Debug Functions

Round Select

Does this earlier '90s Taito game feature the Taito Code? Indeed it does:

• While the game boots up, hold the Service Coin button until a "SERVICE SW ERROR" message pops up on the screen.
• Then, press 1P Start (x3), Service Coin, 1P Start.

A stage select menu should pop up after starting a new game. Press 1P Up/Down to change the round and 1P Button 1 to start a new game. There's no code in the game to control the "Area" portion of this menu, so it's a bit odd that it's even listed.

Object Test Mode

Place the following cheat in MAME's gunfront.xml cheat file to access a debug function after the game boots:

  <cheat desc="Object Test Mode">
    <script state="run">
      <action>maincpu.mw@0143C6=0004</action>
      <action>maincpu.mw@0143C8=97A6</action>
    </script>
    <script state="off">
      <action>maincpu.mw@0143C6=0000</action>
      <action>maincpu.mw@0143C8=2192</action>
    </script>
  </cheat>

The user can press 1P Left/Right to change the color number, but it doesn't seem to do anything. There doesn't seem to be a way to load an actual object on this object test menu.

There's a header for this menu that's never seen -- it's quickly overwritten by the HUD.

(Source: ねこ自慢ブログ (升) Wayder Cheat 0.169)

Unused Graphics

The character graphics ROM still has the work-in-progress name for Battle Shark, for some reason. Sensuikan still means submarine!

(Source: Original TCRF research)

Error Handler Leftovers

Most of the standard 68000 exception vectors have entries in the exception vector table, but they all point to ROM space 0x0F00000. That ROM space might have been used by development hardware while the game was still being tested, but it's empty in the final game. This is identical to the dummied-out handlers in Battle Shark.

Vector	Address
Bus Error	0xF00000
Address Error	0xF00014
Illegal Instruction	0xF00028
Zero Divide	0xF0003C
CHK Instruction	0xF00050
TRAPV Instruction	0xF00064
Privilege Violation	0xF00078
Trace	0xF0008C
Line 1010 Emulator	0xF0009A
Line 1111 Emulator	0xF0009A

(Source: Original TCRF research)