Zaxxon Flip Screen Patch

Technical Description

This tool patches Zaxxon ROMs 1 and 3 (U29 and U27 on PCB) to apply a permanent 180° flip screen patch. The display remains rotated in Upright Mode, exactly as it occurs for Player 2 in Cocktail Mode.

This allows for a flipped orientation without the need for hardware monitor rotation or PCB modifications. Simply dump your original ROMs, upload them here, and flash the patched versions back to your board.

Test Mode Behavior:

M.A.M.E. sets zaxxon / zaxxon2: Test Mode performs all tests and returns correctly.
M.A.M.E. set zaxxon3: Patched successfully, but Test Mode hangs after the RAM check.

Upload your ROM1 & ROM3 dumps together:

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Why use a software flip screen patch for Zaxxon?

Original 1982 Sega Zaxxon PCBs do not have a hardware switch to flip the screen 180 degrees in Upright Mode. Many arcade cabinet restorers or arcade enthusiasts using custom monitor mounts need to rotate the video output. This ROM patch modifies the ROM1 (U29) and ROM3 (U27) code to force the video inversion while the PCB continues to operate in standard Upright Mode.