Genesis Plus GX

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Genesis Plus GX
Genesis plus gx logo.png
Core info
License Proprietary/Non-commercial
Extensions mdx, md, smd, gen, bin, cue, iso, sms, gg, sg

Genesis Plus GX is a Sega 8/16 bit video game system emulator that can be used as a libretro core.


Genesis Plus GX is an open-source Sega 8/16 bit emulator focused on accuracy and portability. The source code, originally based on Genesis Plus 1.3 by Charles MacDonald, has been heavily modified & enhanced, with respect to initial goals and design, in order to improve the accuracy of emulation, implementing new features and adding support for extra peripherals, cartridge & systems hardware.

Feature Support

These are libretro features, not frontend or standalone emulator features.

Saves Save states Rewind Netplay Cheats Controllers API Rumble Sensors Camera Location Subsystem API


Genesis Plus GX supports usage of actual BIOS image files rather than emulating them. Only Sega CD/Mega CD emulation requires a real BIOS to work. It is recommended to use a BIOS from a Model 1 system, but other are expected to work too.

  • bios_CD_E.bin (MegaCD EU BIOS)
  • bios_CD_U.bin (SegaCD US BIOS)
  • bios_CD_J.bin (MegaCD JP BIOS)
  • bios_E.sms (MasterSystem EU BIOS)
  • bios_U.sms (MasterSystem US BIOS)
  • bios_J.sms (MasterSystem JP BIOS)
  • (GameGear BIOS)
  • sk.bin (Sonic & Knuckles (2 MiB) ROM)
  • sk2chip.bin (Sonic & Knuckles UPMEM (256 KiB) ROM)
  • areplay.bin (Action Replay (Pro) ROM)
  • ggenie.bin (Game Genie ROM)


This core has a few options that can be tweaked from the core options menu. The default setting is highlighted and in italics:

  • system_hw (auto/sg-1000/sg-1000 II/mark-III/master system/master system II/game gear/mega drive / genesis)(restart): Choose which system is going to be emulated.
  • region_detect (auto/ntsc-u/pal/ntsc-j)(restart): Choose which region the system is from.
  • force_dtack (enabled/disabled): Emulate system lockups.
  • addr_error (enabled/disabled): Emulate the 68k address error.
  • lock_on (disabled/game genie/action replay (pro)/sonic & knuckles)(restart): Select lock-on cartridge.
  • ym2413 (auto/disabled/enabled): Enable the Master System FM chip.
  • dac_bits (disabled/enabled): Enable YM2612 DAC quantization.
  • blargg_ntsc_filter (disabled/monochrome/composite/svideo/rgb): Enable Blargg NTSC filters.
  • overscan (disabled/top / bottom/left / right/full): Enable borders.
  • gg_extra (disabled/enabled): Extend the Game Gear screen.
  • render (single field/double field): Change how interlaced mode 2 output is handled.
  • gun_cursor (no/yes): Display lightgun crosshair.
  • invert_mouse (no/yes): Invert Mouse Y-axis.

Compatibility List/General Issues

100% compatibility with Genesis / Mega Drive, Sega/Mega CD, Master System, Game Gear & SG-1000 released software (including all unlicensed or pirate known dumps), also emulating backwards compatibility modes when available.


The Genesis Plus GX core supports thirteen different controller settings:

  • MD Joypad 3 Button
  • MD Joypad 6 Button
  • MS Joypad 2 Button (also used for Game Gear)
  • MD Joypad 3 Button + 4-WayPlay
  • MD Joypad 6 Button + 4-WayPlay
  • MD Joypad 3 Button + Teamplayer
  • MD Joypad 6 Button + Teamplayer
  • MS Joypad 2 Button + Master Tap
  • MS Light Phaser
  • MS Paddle Control
  • MS Sports Pad
  • MD XE-1AP
  • MD Mouse
RetroPad MD Joypad 3 Button MD Joypad 6 Button MS Joypad 2 Button
Retro Dpad.png MD Dpad MD Dpad MS/GG Dpad
Retro Y Round.png MD A MD A
Retro X Round.png MD Y
Retro B Round.png MD B MD B MS/GG 1
Retro A Round.png MD C MD C MS/GG 2
Retro L1.png MD X
Retro R1.png MD Z
Retro R2.png
Retro R2.png
Retro Left Stick.png
Retro Right Stick.png
Retro L3.png
Retro R3.png
Retro Select.png MD Mode
Retro Start.png MD Start MD Start GG Start

External Links