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Proto:Dr. Mario (NES)/Virus 1989 & 1990

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This is a sub-page of Proto:Dr. Mario (NES).

Download.png Download Virus (1989 Prototype)
File: Virus (USA) (1989 Proto).nes (64 KB) (info)
Download.png Download Virus (February 2, 1990 Prototype)
File: Virus (USA) (1990 Proto).nes (48 KB) (info)

The 1989 prototype of Dr. Mario is the earliest known build of the game, dumped from a retail NROM board with EPROMs soldered on. At this point, the game is called Virus and has numerous differences from the final version. The game is silent, apart from a few sound effects, and the overall presentation is fairly simplistic and unpolished. The core gameplay, however, is mostly the same.

A slightly newer build (dated February 2, 1990) also exists, which uses a full-size MMC1 development board with socketed EPROMs. The changes in this version are minor: "PUSH START" was added to the title screen, the blank game options were replaced with dashes, the clipboard colors were inverted, and the viruses were animated (the CHR bankswitching code exists in both builds, but the NROM board used by the 1989 build does not support bankswitching). The PRG is otherwise identical.

Judging from the existence of MMC1 initialization and bankswitching code and the absence of some graphics in 2-player mode, it's likely that the 1989 build was "cut down" to fit on an NROM board. Why this was done is anyone's guess.

To do:
Add various missing unused bits.


At this point in development, much of the game's code is based on Nintendo's NES Tetris, released in November 1989. The startup and NMI routines are virtually identical, as is the sound code; in fact, all of the sound effects used at this point are merely double-speed versions of those used in Tetris (the game calls the sound code twice per frame, for unknown reasons). The original music tracks are still present, and can be played by writing a track number to RAM address $6F5.

Title Screen

Virus 1989 Proto Virus 1990 Proto Dr. Mario Final
Very bland if you ask me. Oh, thanks, I thought I'd be trapped on this screen forever! Much better.

The title screen is simply Virus written in purple on a blue box with a syringe injecting the V, and a completely black background. Mario isn't present, and the 2-Player option can't be selected here.

Options Screen

Virus 1989 Proto Virus 1990 Proto Dr. Mario Final
Boo, no music. Still no music. Yay, music!

The menu simply says "MENU", and has a solid blue background. Press A or B to adjust the various options. This causes a sound effect to play, but nothing is heard when the cursor is moved.

This menu has a few features that the final game doesn't have at all:

  • The "FALL DOWN" option determines whether Megavitamin halves fall down. The programming for this option actually survived into the final game, and can be enabled in any version by changing RAM address $724 to a non-zero value.
  • The virus level can be set up to 24. In the final, it can only be set up to 20 until the player has cleared Level 23.
  • "SET COUNT" determines how many wins a player must achieve in 2-Player mode. In the final, you can only have 3-set games; why they removed this option is a mystery, though this feature still exists in the final version. The number can be changed at RAM address $725.
  • "GAME LEVEL" (called "SPEED" in the final) can only be set to EASY or NORM, though a HARD setting does exist and can be accessed by setting RAM address $726 to 01. This completely disables the pill-throwing animation, causing Megavitamins to immediately appear at the top of the bottle.
  • The "MUSIC TYPE" option does not yet exist.
  • There are two blank, non-functional options between "FALL DOWN" and "PLAYER".
  • A hidden, unused option to disable periodic speedups exists, though it can only be activated by changing RAM address $723 to a non-zero value. Much like FALL DOWN, its programming remains in the final game.
  • There are hidden words within the ROM that are not seen/used anywhere: "TWO", "ONE", "COLOR", and "ATACK" (spelled incorrectly). They can be seen in-game by editing the "GAME LEVEL" option to HARD and then pressing A to scroll through some weird selections. These were probably meant to be in place of the existing options.

1-Player Game

Virus 1989 Proto Dr. Mario Final
Dog and nurse. Yea, I think the viruses look better.
  • Probably the most obvious difference is the panel on the left. From the PlayChoice-10 build onward, it shows the viruses dancing in a circular object (a Petri dish in the PC-10 build, a magnifying glass afterward), but originally it was a hospital scene showing a frowning cartoon dog sitting on a chair in front of a woman resembling Nurse Peach. The dog sneezes every six seconds, but this does not have a sound effect. The woman is holding an icepack.
  • The viruses have completely different designs, and are not animated. However, the necessary CHR bankswitching code is present, and will function properly if the game is run on an MMC1 board with the 1990 build's CHR data.
  • The clipboards are colored differently, with black paper and purple edges.
  • The pills don't have their outlines yet.
  • Dr. Mario looks considerably different. Only his pill-tossing animation has been implemented at this point.
  • The background is solid blue, whereas the final has a checkered background that changes color depending on the game speed.
  • The Virus logo is displayed on the top-right, and is identical to the one used on the title screen.
  • The right-hand clipboard has a "PIL" counter showing how many Megavitamins have been tossed into the bottle. This was replaced with the speed level in the PlayChoice-10 and later builds.
  • When starting a new game at Level 1, sometimes a virus color will be missing from the playfield. The final game always starts with all three colors present.
  • The default high score is 5,000. The player's score also caps at 999,999, which was later increased to 9,999,999.
  • When you lose the game, the word "MISS" is displayed on the playfield before "GAME OVER" appears.
Virus 1989 Proto Dr. Mario Final
Let's try the next stage! We don't know what to try next, but at least we're told to press Start.

Beating a level displays "CLEAR! TRY NEXT STAGE", which was rearranged into "STAGE CLEAR TRY NEXT" in the final. The final also shows a flashing "START" sprite.

2-Player Game

Virus 1989 Proto Virus 1990 Proto Dr. Mario Final
Virus19892PGameplay.png Virus19902PGameplay.png DrMario2PFinal.png
  • As mentioned above, the player can choose anywhere from 1- to 5-set matches. In Dr. Mario, you are stuck with 3-set matches.
  • The virus level and speed are shared between both players. In the final version, each player can set these individually.
  • The game speed and 1P/2P markers are missing.
  • Both the clipboard and the inner corners of the bottles in the 1989 build reference tiles that only exist in the 1990 build.
Virus 1989 Proto Dr. Mario Final
Virus19892PGameClear.png DrMario2PClearFinal.png
  • At the end of a set, "WIN!" and "MISS" are displayed over the winner's and loser's playfield, respectively. In the final game, the loser gets an animation of the Red Virus holding a large red "X".
  • The crowns denoting each player's win count are much smaller.
Virus 1989 Proto Dr. Mario Final
Virus19892PMatchClear.png DrMario2PGameClearFinal.png

Dr. Mario doesn't appear in the winner's playfield when the match ends. "PUSH START" was changed into a "START" sprite and moved to the bottom of the screen in the final game.

Unused Graphics

These seem to be tiles. They remained, still unused, through to the PlayChoice-10 build.

A healthy dog is a happy dog.
The cartoon dog smiling, likely meant to be used when a level is cleared (since he seems to be the patient and all). However, he still frowns and sneezes as if nothing happened.

Graphical Changes

Dr. Mario

Virus 1989 Proto Dr. Mario Final
Dr. Derp.
Dr. More-lively-than-derp.

Mario himself looks quite different: a brown outline instead of black, no stethoscope, smaller eyes, a straight arm (bent in the final), and realistic white shoes rather than his traditional brown ones.


Virus 1990 Proto Dr. Mario Final
Inky! Blinky! Clyde! Nice day today, huh? Yeah... This one's barely moving a thing. The "Dr. Mario" viruses look better, but not by a long shot. Not that anyone really cares because these are like 8×8 big.

The viruses look completely different at this point, and a bit...weird. As mentioned above, they are only animated in the 1990 build.