Sega MS/GG/MD/CD (Genesis Plus GX)Link

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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.

Why use this core?Link

Awaiting description.

How to get and install the Genesis Plus GX core:Link

  1. Start up RetroArch. Inside the main menu, go to 'Online Updater'.

  2. Just to make sure we have the latest info files, select 'Update Core Info FIles'. Wait until this is done. Then, select 'Core Updater'.

  3. Browse through the list and select 'Sega MS/GG/MD/CD (Genesis Plus GX)'.

After this has finished downloading, the core should now be ready for use!

How to start (after installation):Link

  1. Go back to RetroArch's main menu screen. Select 'Load Content'.

  2. Browse to the folder that contains the content you want to run.

  3. Select the content that you want to run.

  4. If you are asked which core to select, choose 'Sega MS/GG/MD/CD (Genesis Plus GX)'.


  • Charles McDonald
  • Eke-Eke

See alsoLink

Sega 16-bit coresLink


A summary of the licenses behind RetroArch and its cores have found here.


Content that can be loaded by the Genesis Plus GX core have the following file extensions:

  • .mdx
  • .md
  • .smd
  • .gen
  • .bin
  • .cue
  • .iso
  • .sms
  • .gg
  • .sg
  • .68k
  • .chd


RetroArch database(s) that are associated with the Genesis Plus GX core:


Required or optional firmware files go in RetroArch's system directory.

Filename Description md5sum
bios_MD.bin MegaDrive TMSS startup ROM (bootrom) - Optional 45e298905a08f9cfb38fd504cd6dbc84
bios_CD_E.bin MegaCD EU BIOS - Required for MegaCD EU games e66fa1dc5820d254611fdcdba0662372
bios_CD_U.bin SegaCD US BIOS - Required for SegaCD US games 854b9150240a198070150e4566ae1290
bios_CD_J.bin MegaCD JP BIOS - Required for MegaCD JP games 278a9397d192149e84e820ac621a8edd
bios_E.sms MasterSystem EU BIOS (bootrom) - Optional -
bios_U.sms MasterSystem US BIOS (bootrom) - Optional -
bios_J.sms MasterSystem JP BIOS (bootrom) - Optional - GameGear BIOS (bootrom) - Optional -
sk.bin Sonic & Knuckles ROM (lock-on) - Optional 4ea493ea4e9f6c9ebfccbdb15110367e
sk2chip.bin Sonic & Knuckles UPMEM ROM (lock-on) - Optional b4e76e416b887f4e7413ba76fa735f16
areplay.bin Action Replay ROM (lock-on) - Optional -
ggenie.bin Game Genie ROM (lock-on) - Optional -


BIOS files that are labelled (bootrom) and (lock-on) must have their corresponding core option ('System bootrom' core option or 'Cartridge lock-on' core option) configured correctly in order for them to be loaded.


RetroArch features that the Genesis Plus GX core respects.

Feature Supported
Core Options
RetroArch Cheats
Native Cheats
Multi-Mouse -
Disk Control
Crop Overscan


The Genesis Plus GX core's directory name is 'Genesis Plus GX'

The Genesis Plus GX core loads from and saves to to these directories.

RetroArch's Save directory

  • 'content-name'.srm (MS/GG/MD/Pico/SG-1000 Cartridge Backup save)
  • scd_E.brm (Mega CD EU BIOS Backup RAM) When the 'CD System BRAM' core option is set to per bios
  • scd_U.brm (Sega CD US BIOS Backup RAM) When the 'CD System BRAM' core option is set to per bios
  • scd_J.brm (Mega CD JP BIOS Backup RAM) When the 'CD System BRAM' core option is set to per bios
  • 'content-name'.brm (Sega CD/MegaCD Per-game Backup RAM) When the 'CD System BRAM' core option is set to per game
  • cart.brm (Sega/Mega CD RAM CART)

RetroArch's State directory

  • 'content-name'.state# (State)

Geometry and timingLink

The Genesis Plus GX core's internal FPS is (FPS).

The Genesis Plus GX core's internal sample rate is (Rate)

The Genesis Plus GX core's core provided aspect ratio is dependent on the 'Core-provided aspect ratio' core option.

Loading Sega CD gamesLink

When loading Sega CD games, Genesis Plus GX needs a cue-sheet that points to an image file. A cue sheet, or cue file, is a metadata file which describes how the tracks of a CD or DVD are laid out.

If you have e.g. foo.bin, you should create a text file and save it as foo.cue. If the Sega CD game is single-track, the cue file contents should look like this:


 FILE "foo.bin" BINARY
  TRACK 01 MODE1/2352
   INDEX 01 00:00:00

After that, you can load the foo.cue file in RetroArch with the Genesis Plus GX core.

Certain Sega CD games are multi-track, so their .cue files might be more complicated.

Core optionsLink

The Genesis Plus GX core has the following option(s) that can be tweaked from the core options menu. The default setting is bolded.

Settings with (Restart) means that core has to be closed for the new setting to be applied on next launch.

  • System hardware (auto/sg-1000/sg-1000 II/mark-III/master system/master system II/game gear/mega drive / genesis):

Choose which system is going to be emulated.

  • System region (auto/ntsc-u/pal/ntsc-j):

Choose which region the system is from.

  • System lockups (Off/On):

Emulate system lockups that occur on real hardware.

  • System bootrom (Off/On):

Runs bootrom if available and then starts loaded content after the boot sequence. Look above at the BIOS section for more information.

  • CD System BRAM (per bios/per game):

The Sega CD's internal memory cannot hold a lot of saves. Setting this core option to per game allows each game to have its own one brm file, thus negating any lack of available space issues.

  • 68k address error (Off/On):

Emulate the 68k address error that occurs on real hardware. Set this to off when playing rom hacks since most emulators used to develop rom hacks don't emulate the error.

  • Cartridge lock-on (Off/game genie/action replay (pro)/sonic & knuckles):

Select lock-on cartridge. Look above at the BIOS section for more information.

  • Master System FM (auto/Off/On):

Enable the Master System FM chip. (Enhanced sound output support for SMS compatible games.)

  • YM2612 DAC quantization (Off/On):

for Mame core only. Awaiting description.

  • YM2612/YM3438 core (mame/nuked (ym2612)/nuked (asic ym3438)/nuked (discrete ym3438):

Awaiting description.

  • Sound output (stereo/mono):


  • Audio filter (Off/low-pass):

Awaiting description.

  • Low-pass filter % (5 to 95 in increments of 5. 60 is default):

Awaiting description.

  • Blargg NTSC filter (Off/monochrome/composite/svidio/rgb):


Blargg NTSC filter - Off

Blargg NTSC filter - monochrome

Blargg NTSC filter - composite

Blargg NTSC filter - svideo

Blargg NTSC filter - rgb

  • LCD Ghosting filter (Off/On):


LCD Ghosting filter - On


  • Borders (Off/ top/bottom/ left/right / full):

Self explanatory.

  • Game Gear extended screen (Off/On):


Game Gear extended screen - Off

Game Gear extended screen - On

  • Core-provided aspect ratio (auto/NTSC PAR/PAL PAR ):

Choose the Core-provided aspect ratio. RetroArch's aspect ratio must be set to Core provided in the Video settings for this to function properly.

  • Interlaced mode 2 output (single field/double field):

Change how interlaced mode 2 output is handled. Games like Sonic 2's multiplayer mode uses Interlaced Mode 2.

Interlaced mode 2 output - single field


Interlaced mode 2 output - double field


  • Show Lightgun crosshair (Off/On):

Shows lightgun crosshairs for the 'MD Menancer', 'MD Justifiers', and 'MS Light Phaser' Device Types.

Lightgun crosshair


  • Invert Mouse Y-axis (Off/On):

Inverts the Mouse Y-axis for the 'MD Mouse' Device Type

  • CPU speed (100% to 200% in increments of 25%. 100% is default):

Overclock the emulated CPU.

  • Remove per-line sprite limit (Off/On):



Device typesLink

The Genesis Plus GX core supports the following device type(s) in the controls menu, bolded device types are the default for the specified user(s):

User 1 device typesLink

User 2 device typesLink

Other controllersLink

The Genesis Plus GX can also emulate Pico touch controls but this is done automatically and cannot manually selected as a Device Type through RetroArch's Controls menu.

Controller tablesLink

Joypad and analog device type tableLink

User 1 - 8 input descriptors RetroPad Inputs MD Joypad 3 Button MD Joypad 6 Button MS Joypad 2 Button MS Paddle Control MS Sports Pad MD XE-1AP
B B B 1 1 1 E2
A A A E1
Mode Mode Select
Start Start Start Start Start Start Start
D-Pad Up D-Pad Up D-Pad Up D-Pad Up
D-Pad Down D-Pad Down D-Pad Down D-Pad Down
D-Pad Left D-Pad Left D-Pad Left D-Pad Left
D-Pad Right D-Pad Right D-Pad Right D-Pad Right
C C C 2 2
N/A X Paddle X Trackball X Thumb-stick X
N/A Y Paddle Y Trackball Y Thumb-stick Y
N/A X Slider Y
N/A Y Slider X

Mouse device type tableLink

User # input descriptors RetroMouse Inputs MD Mouse Graphic Board Pico
N/A Mouse Pointer Pointer
N/A Left button Pen Pen button
N/A Right button Menu Red button
N/A Mouse Wheel Down Center button
N/A Start Do

Lightgun device type tableLink

User # input descriptors RetroLightgun Inputs MD Menancer MD Justifiers MS Light Phaser
N/A Gun Crosshair Crosshair Crosshair
N/A Gun Trigger A A A
N/A Gun Turbo B B B
N/A Gun Pause C C C
N/A Gun Start Start Start Start


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. It also has Pico emulation.