Mike Tyson's Punch-Out!! 2P Versus hack

This hack lets a second player control the opponent boxer.

Base ROM: Mike Tyson's Punch-Out!! (Japan, USA) (Rev A)

• SHA-1 0f0c2c2e294ff8ce255a618964728c935fd8963b
• iNES file with a 16-byte header, mapper 9 (MMC2)

Turning on 2-player mode

• Plug in a second controller.
• During a fight, press Start on controller 2. A short tone confirms that player 2 now controls the opponent.
• Press Start on controller 2 again to give the opponent back to the computer. It plays a different tone.
• 2-player mode stays on from fight to fight until it is toggled off or the console is reset.
• If nobody presses Start on controller 2, the game plays exactly like the original.

Player 2 controls

Input	Action
B	Punch 1 (usually a jab)
A	Punch 2 (usually a hook)
Up + B / Up + A	Alternate punches (uppercut, smash, etc.)
Down + B / Down + A	More punches, for boxers that have them
Select	Special move (see below)
Left or Right	Dodge
Hold Up	High guard: blocks Mac's face punches, leaves the body open
Up not held	Low guard: blocks body punches, leaves the face open

These rules apply to player 2's moves:

• Moves start only when the opponent is standing idle, the same way the computer's moves do. A button pressed slightly early is remembered for 8 frames.
• Every punch keeps its original animation, wind-up, hit timing, damage and weak spots. Mac can dodge, block and counter as usual.
• A dodge works only with good timing. Press it within about 10 frames of Mac starting a punch.

Special moves (Select)

Boxer	Select
Glass Joe	Backs up, then lunges with a jab
Von Kaiser	(none)
Piston Honda 1 and 2	Honda Rush: backs up, then 4 alternating punches
Don Flamenco 1 and 2	Taunt
King Hippo	Taunt
Great Tiger	Tiger punch. It knocks Mac down if it lands.
Bald Bull 1 and 2	Bull Charge. It knocks Mac down if it lands.
Soda Popinski	Taunt
Mr. Sandman	Dreamland Express uppercut (also on Down+B)
Super Macho Man	Spinning punch
Mike Tyson	Uppercut. It knocks Mac down if it lands.

The move names come from what each animation does in the game: how much damage it deals and how it looks in captured frames. Some labels, especially the taunts, may not match the official names.

How it works

The opponent's behavior is normally driven by "behavior scripts". These choose which animation to play next (jab, hook, taunt, pause, and so on). Separately, a defense routine decides when to dodge and which guard to hold. The hack changes two JSRs in the fight loop:

Address	Original	New
$A69F	JSR $C291 (defense AI)	JSR DefHook
$A6A2	JSR $B196 (behavior script)	JSR AtkHook

In 1-player mode, both hooks jump straight to the original routines.

In 2-player mode, the hooks work like this:

• AtkHook reads controller 2 and asks for the matching animation through the game's normal request byte ($90 = $80 | anim). Only idle opponents can start a move.

• DefHook sets the guard with the game's own guard-switch flag ($04FF). It also starts the dodge animation ($83) on Left/Right.

• Unstick covers two jobs the behavior scripts would normally do:

  • It returns a dodge to idle when Mac never punched, or when the dodge runs too long (some dodges wait for Mac to do something a tired Mac never does).
  • It restarts the round clock when both boxers have been standing idle with the clock stopped.

• Tired Mac: Mac normally recovers from being tired (pink, out of hearts) by dodging or blocking the opponent's punches. Player 2 might never punch, so each 2 seconds that both boxers stand idle counts as one dodge. Mac recovers after about 2–8 seconds, depending on the opponent.

Free space and RAM used:

• Code and tables sit at $F900–$FBA5 of the fixed bank, which was all zeros.
• RAM $23–$2F is used; the original game never writes it after boot.

Move tables: moves.py holds the move tables. Each opponent has 8 slots: B, A, U+B, U+A, D+B, D+A, Select, and one unused. Each slot holds an opponent animation ID. Multi-part moves (Glass Joe's lunge, the Honda Rush) are listed in SEQ. If Mac lands a hit, the rest of the sequence is cancelled. Edit the table and rebuild to remap moves.

Tuning values are also in moves.py:

• CD_ATTACK: idle frames required between moves
• CD_DODGE: idle frames after a dodge
• DODGE_LOCK: how long after a move before dodging is allowed
• BUF_FRAMES: how long an early button press is remembered
• SFX_ON / SFX_OFF: the toggle sounds
• CLOCK_RESTART: idle frames before the stopped clock restarts
• TIRED_RECOVER: quiet frames (both boxers idle) that count as one dodge for a tired Mac
• DODGE_MAXWAIT / DODGE_HARDMAX: longest a dodge can last while Mac isn't punching / at all

Building

You need cc65 (ca65 and ld65) and Python 3.

CC65BIN=/path/to/cc65/bin python3 build.py original.nes output.nes
python3 mkips.py original.nes output.nes patch.ips

Known limits

• A few computer-only behaviors are skipped in 2-player mode. Examples are scripted pauses, some star-punch openings, and special patterns tied to the clock, such as Tyson's first 90 seconds. Every animation still works normally.
• The pre-fight intro and the knockdown get-up rules are unchanged.
• Testing was done in an emulator, using scripted inputs on both controllers for all 14 fights. It has not been tested on real hardware yet.

Changes

• v1.3: Piston Honda's Select is now the full Honda Rush, as in the original game: he backs up, then throws 4 alternating punches. Moves can now be sequences of any length.
• v1.2: A tired Mac now recovers on his own if both boxers stand idle. Before, he stayed pink forever when player 2 didn't punch.
• v1.1: Fixed a freeze where a dodge could hang forever while Mac was tired (pink). When this happened, Start on controller 2 seemed to stop working, because neither player 2 nor the computer can act until the dodge ends. Dodges now always end.
• v1.0: First release.

Passwords

The hack doesn't change how passwords work.

• Entering the well-known codes gives the same result as in the original, for example 007 373 5963 (Tyson) and 005 737 5423.
• With the same fight record, the original, the hack in 1-player mode and the hack in 2-player mode all give the same password. In my test that was 069 733 5423 after a 1-0, 1 KO record.

The password the game shows encodes Mac's career wins, losses and KOs. The codes in guides assume a perfect record (every fight won by KO). Any loss, decision win or TKO, which happens a lot in 2-player fights, gives a different code. That code still works and restores that exact record.