Millipede (Arcade)

To do: There appears to be a secret message on the self test if you place the PROM at a GFX slot; see Talk:Centipede (Arcade)

The caterpillar is back, and with several other insect friends to ruin your day even more.

Unused Graphics#

There are two unused sprites loaded into VRAM that store two names in the same graphics area. Using two different palettes, it's possible to see either name clearly by turning one colour black. In the examples below, the unused colour for each name will be dimmed.

Ed Logg's last name in white as a sprite, likely as a developer Easter egg. These tiles also contain the name "Snyder" in red, likely referring to Doug Snyder, engineer/technician for Atari at the time (also represented on the default high score list by "DUG", right below "ED" Logg).

"Atari" in white as a sprite, overlaid with Ed Logg's last name in red, using an identical design to the above graphic.

Anti-Piracy#

Due to a rise of copies and pirated arcade cabinets of previous games, Atari made increased efforts to prevent such cases in their arcade games starting from the 1980s. Like many of Atari's arcade games at the time, it will cripple gameplay if certain checksum checks fail. These checks are backported from the game's predecessor, just using different variable locations.

Copyright String Checksum#

During the title screen, the game runs a checksum of the "COPYRIGHT ATARI 1982" copyright string and stores the result in 0xFF. If this value is not 1 due to changing the first A in "ATARI", then every 128 frames (about 0.5 seconds) the game runs arbitrary code from a register that easily breaks the game to the point of being unplayable.

Draw Copyright String Checksum#

The code to draw the copyright string is located at 0x2326. Whenever the copyright string is drawn on the title screen, the game runs a checksum on this code to see if the code to drawing the copyright string has been modified, and stores the result at 0xF9. If this value is not 0, the game crashes due to loading an invalid address set by the value.

Genuine Hardware Check#

The game checks for a POKEY pseudorandom number generator chip to ensure that it is being run on genuine hardware from Atari. If the game is unable to generate a random number from the chip when the instruction to do so is called, the game freezes.

Hidden Message#

The hidden Morse code message from Centipede is still here, and is at 0x3FF in the main CPU ROM at ROM offset 4000. Notably, the year was updated to 1982.

        hex 02      bb      5a      30      5f      ee      1d      a8
     binary 0000001010111011010110100011000001011111111011100001110110101000
dots+dashes ......-.-.---.--.-.--.-...--.....-.--------.---....---.--.-.-...
with spaces ...... -.-. --- .--. -.-- .-. .. --. .... - .---- ----. ---.. ..--- .- - .- .-. .
    decoded        C    O   P    Y    R   I  G   H    T 1     9     8     2     A  T A  R   I