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Mortal Kombat (Arcade)

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Title Screen

Mortal Kombat

Developer: Midway Games
Publishers: Midway Games, Taito (JP)
Platform: Arcade (Midway Y Unit (Versions until 4.0), Midway T Unit (Versions 4.0-5.0))
Released in US: October 8, 1992

DevTextIcon.png This game has hidden development-related text.
GraphicsIcon.png This game has unused graphics.
MusicIcon.png This game has unused music.
TextIcon.png This game has unused text.
DebugIcon.png This game has debugging material.
Carts.png This game has revisional differences.

BugsIcon.png This game has a bugs page

Mortal Kombat is a fighting game that had a strong following, caused a video game violence discussion at the American Senate level, and also was in competition with Street Fighter II.

To do:
  • The revisional differences are quite a mess.
  • Prerelease stuff posted on Ed Boon's Twitter for the game's 30th anniversary, along with other behind-the-scenes information (like Sonya replacing Jax apparently.)

EJB Menu

The EJB Menu is an alternate test menu that can be accessed through this button code in attract mode:
1P Block (×5), 2P Block (×10), 1P Block (×2), 2P Block, 1P Block (×2), 2P Block (×3), 1P Block (×4).

(Converted to letters, these numbers spell out "EJB ABCD".)

The timing on this code is extremely tight, so you might have to try multiple times before it registers. The following MAME codes will simplify the code to 2P Block, 1P Block (×4):

Revision 1.0: mkla1.xml
Revision 2.0: mkla2.xml
Revision 3.0: mkla3.xml
  <cheat desc="Simplified EJB Code">
    <script state="run">
  <cheat desc="Simplified EJB Code">
    <script state="run">
  <cheat desc="Simplified EJB Code">
    <script state="run">
Revision 4.0: mkla4.xml
Revision 5.0: mk.xml
  <cheat desc="Simplified EJB Code">
    <script state="run">
  <cheat desc="Simplified EJB Code">
    <script state="run">

You're never going to see this in an actual arcade.

  • Diagnostics Tests - Identical to normal test menu.
  • Coin Bookkeeping - Identical to normal test menu.


  • Game Audits - Identical to normal test menu except in revision 5.0, where six extra audits will be displayed:
Sec Chip Failure
Error Traps
FrameA9 Errors
System Lockups
Illegal Opcodes
Green Ninja Counter (probably related to the hidden Reptile fight)


  • Hello - Displays this screen of shout-outs for ten seconds, then exits the EJB menu. "Leslie" is only credited in versions 3.0 and above.
  • Enter Initials - Jumps to the high score initials screen. The number of wins seems to be random, but it increases every time.


  • Character Endings - Jumps to a new sub-menu. This displays the selected character's ending and the game credits.
(Source: Original TCRF research)

Unused Sprites

Goro turning to stone and breaking. Possibly meant to be used as a dying animation.

Johnny Cage doing some sort of flip. He does have a similar move in Mortal Kombat: Deadly Alliance as part of his Karate fighting style and in Mortal Kombat (2011) as a special move. It's possible this was meant as a special move or Fatality.

Shang Tsung laughing, which may have been meant as a win pose. Shang Tsung does laugh in the sequel.

MK1 ShangTsungClapping.gif
Unused sprite of Shang Tsung possibly clapping in the Throne Room background.

Shang Tsung actually using his sword. It has been noted in the past that he was originally meant to have a Fatality where he beheaded his opponent. He does get to use a sword in Mortal Kombat: Deadly Alliance but not as his fatality.

(Source: Red Sumac)

Unused Music

This track is used in prototype versions 8.0 and 9.0 when Goro first appears. For whatever reason, the released versions just play the Goro's Lair track again. The track is still in the game, however.

(Source: Original TCRF research)

Unused Text

Present in ROM chips mkt-ug12 / mkt-uj12 (interleaved).

Temp Bio Text

MK1 SansBio.png

Located at 0x9262D, after Sonya Blade's bio text:


Possibly a placeholder for characters whose bios hadn't been written yet. If you force the game to load the values for what would be Shang Tsung's and Goro's biographies, this text will be displayed. Since they are bosses and the game won't ever display their bios normally, they probably just plugged in SANS BIO for them.

Old Copyright String

Located at 0x929C2:


Most likely a leftover text from another game.

Unused Intro Text

Text starts at 0xBAAAA:


Possible alternate intro text for "GORO LIVES..." ?

Unused Audits

There are two unused audits in the game. Audit text starts at 0xC1FC6:


" S TAKEN" is probably a coin counter, while "DOOR SLAMS" would count the number of cabinet tilts. Similar audits appear in other Midway Y Unit games.

Hidden Credit

Present at 0xFFDF1785 in the main CPU.


This credit was discovered in-game on May 10, 2021 by TotalMK on YouTube. In order to access it, the player must hold down High Punch while inputting the above EJB menu code. Note that the screen will disappear and return to the EJB menu when High Punch is released.

The hidden credit as seen in-game.


Oh cool, the audit menu! I must be really lucky to see this. Wait, what's this "Ermacs" thing? I think that means to start a rumor!

Present in the audit menu (but only in the Y-Unit versions) is a listing for "Ermacs" which, due to being under the Reptile listings, started a popular rumor that Ermac was a hidden character that would be fought/unlocked when certain conditions were met. In reality, "Ermacs" refers to "Error Macros", a log for the developers for when the game crashed unexpectedly...but in the final version the counter can't actually go up and is just for show.

A little more background for this could be found in GamePro Issue 054 January 1994 page 34, where Ed Boon compares it to the Smash TV Warp Zone glitch. It would basically recover the system and put you back in the game, but the game creators called that glitch the Hidden Key Room. Ermacs or Error Traps (as listed in earlier revisions) which is shortened from Error Macro is similar to that. A programming technique to quell user errors (such as entering numbers when only letters are accepted.). What Ed did was by putting a counter of those errors that started in Smash TV, he decided to put a counter in the prototype revisions (listed as Error Traps) and later called it Error Macros, which led to the famous ERMACS counter. He even admitted this was not a character, but a counter for traps.

Ermac became a playable character beginning in Ultimate Mortal Kombat 3, with his backstory using the rumor as a base.

(Source: Pop Fiction - I AM ERMAC)
(Torentsu: Original TCRF research)

Revision Differences

To do:
Shouldn't some of these be in the Proto namespace?
Please elaborate.
Having more detail is always a good thing.
Specifically: Document the missing prototypes and perform additional research.

A number of different versions of MK1 were released over time.

Prototype 4.0

Dated July 14th, 1992. The earliest known version dumped.

To do:
Research and rewrite this bit.
  • You can't play as the same character. In fact, the cursors in the character select will actually block each other from inhabiting the same space!
  • Sub-Zero has new corner infinite (ex. uppercut, freeze and repeat).
  • Sub-Zero has faster recovery after slide and can go straight into sweep for most instances.
  • Sub-Zero can freeze the opponent in the air for 'Finish Him/Her' as he's falling from an uppercut, and do fatality in the air and the body will fall to the ground frozen.
  • Liu Kang can do Flying Kick when you do a HK first in air than F, F HK.
  • Raiden can now do Torpedo after doing a jumping kick for more combo possibilities.

Prototype 8.0

Dated July 21, 1992.

To do:
Document further.

Prototype 9.0

Dated July 28, 1992.

To do:
Document further.

Revision 1.0

Dated August 9, 1992. The first official release of the game.

  • Fixed the "multiple corner uppercut trick".
  • Made Goro easier to knock down.
  • Replaced the song that plays when Goro first appears (as listed above) with the Goro's Lair theme again, for some reason.

Revision 2.0

Dated August 18, 1992.

  • Added the ability for both players to select the same character.
  • Added a death sequence for Shang Tsung.
  • Added the merchendise promo screen to the attract mode.
  • More blood!

Revision 3.0

Dated August 31, 1992.

  • Improved the AI on computer opponents.
  • Added the infamous Reptile!
  • Added a DIP switch setting to toggle the comic book offer in the attract mode.

Revision 4.0

Dated September 28, 1992.

  • Added the clues on how to find Reptile, like the shadows on the moon.
  • Kano and Sonya can now fight Reptile.
  • You're now allowed to block during fatalities.
  • Goro's theme now plays during all of the Endurance rounds.

Revision 4.0 T-Unit

Dated February 11, 1993. This update was actually more than just a ROM chip replacement: The game was ported to the newer "T-Unit" hardware used by Mortal Kombat II.

  • "ERMACs" counter removed from Game Audits.

Revision 5.0 T-Unit

Dated March 19, 1993.

  • Misc. bug fixes.
  • Performing a Pit Fatality no longer rewards points.
(Source: MAME History.dat)
(Source: MK Secrets)