Libretro Genesis Plus GX is an open-source 8/16-bit Sega emulator focused on accuracy and portability.
The source code, originally based on Charles MacDonald's Genesis Plus 1.3, has been heavily modified and enhanced, with respect to the original goals and design, to improve emulation accuracy, implement new features and add support for additional peripherals, cartridges and system hardware.
Genesis Plus GX is 100% compatible with Genesis/Mega Drive, Sega/Mega CD, Master System, Game Gear, SG-1000 and Pico software (including all known unlicensed and pirate dumps), also emulating backwards compatibility modes when available.
¶ 
License
This core is under non-commercial license.
¶ 
Compatibility
| RPI0/RPI1 | RPI3 | RPI4/RPI400 | RPI5 | ODROID XU4 | OGA/OGS/RG351 | PC | RG353 |
|---|---|---|---|---|---|---|---|
| ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ |
¶ 
Features
| Feature | Supported |
|---|---|
| Restart | ✔ |
| Saves | ✔ |
| States | ✔ |
| Rewind | ✔ |
| Netplay | ✔ |
| Core Options | ✔ |
| RetroAchievements | ✔ |
| RetroArch Cheats | ✔ |
| Controls | ✔ |
| Remapping | ✔ |
| Multi-Mouse | ✔ |
¶ 
BIOS
¶ List of mandatory bios
| Filename | Description | MD5 | Provided |
|---|---|---|---|
| bios_CD_E.bin | EU MegaCD BIOS (bootrom) | e66fa1dc5820d254611fdcdba0662372 | ❌ |
| bios_CD_U.bin | US SegaCD BIOS (bootrom) | 2efd74e3232ff260e371b99f84024f7f | ❌ |
| bios_CD_J.bin | JP MegaCD BIOS (bootrom) | 278a9397d192149e84e820ac621a8ed bdeb4c47da613946d422d97d98b21cda | ❌ |
¶ Location
Put the bios like this:
┣ 📁 recalbox
┃ ┣ 📁 share
┃ ┃ ┣ 📁 bios
┃ ┃ ┃ ┣ 📁 segacd
┃ ┃ ┃ ┃ ┣ 🗒 bios_CD_E.bin
┃ ┃ ┃ ┃ ┣ 🗒 bios_CD_U.bin
┃ ┃ ┃ ┃ ┣ 🗒 bios_CD_J.bin
¶ 
Isos
¶ Supported extensions
Isos must have the extension:
- .bin/.cue
- .chd
- .iso
¶ Location
Put the isos like this:
┣ 📁 recalbox
┃ ┣ 📁 share
┃ ┃ ┣ 📁 roms
┃ ┃ ┃ ┣ 📁 segacd
┃ ┃ ┃ ┃ ┣ 🗒 game.iso
The isos using Redump format are highly recommended.
For more information about isos, go to this tutorial!
¶ 
Advanced configuration of the emulator
To be able to keep your custom configurations during an upgrade, we advise you to use our configuration override feature.
¶ Accessing to options
You can configure various options in two different ways.
- Via RetroArch menu:
┣ 📁 RetroArch Menu
┃ ┣ 📁 Core options
┃ ┃ ┣ 🧩 Name_option
- Via the file
retroarch-core-options.cfg:
┣ 📁 recalbox
┃ ┣ 📁 share
┃ ┃ ┣ 📁 system
┃ ┃ ┃ ┣ 📁 configs
┃ ┃ ┃ ┃ ┣ 📁 retroarch
┃ ┃ ┃ ┃ ┃ ┣ 📁 cores
┃ ┃ ┃ ┃ ┃ ┃ ┣ 🧩 retroarch-core-options.cfg
¶ Core options
| Options | Options values | Variables (for configuration override) | Variables values |
|---|---|---|---|
| System Hardware | Auto ✅ / SG-1000 / SG-1000 II / SG-1000 II + RAM Ext. / Mark III / Master System / Master System II / Game Gear / Mega Drive/Genesis |
genesis_plus_gx_system_hw |
auto / sg-1000 / sg-1000 II / sg-1000 II + ram ext. / mark-III / master system / master system II / game gear / mega drive / genesis |
| System Region | Auto ✅ / NTSC-U / PAL / NTSC-J |
genesis_plus_gx_region_detect |
auto / ntsc-u / pal / ntsc-j |
| System Boot ROM | Disabled ✅ / Enabled |
genesis_plus_gx_bios |
disabled / enabled |
| CD System BRAM (Requires Restart) | Per-BIOS ✅ / Per-Game |
genesis_plus_gx_bram |
per bios / per game |
| CD Backup Cart BRAM (Requires Restart) | Per-Cart ✅ / Per-Game |
genesis_plus_gx_cart_bram |
per cart / per game |
| CD Backup Cart BRAM Size (Requires Restart) | Disabled ✅ / 128 kbit / 256 kbit / 512 kbit / 1 Mbit / 2 Mbit / 4 Mbit ✅ |
genesis_plus_gx_cart_size |
disabled / 128k / 256k / 512k / 1meg / 2meg / 4meg |
| CD add-on (MD mode) (Requires Restart) | Auto ✅ / Sega/Mega CD / MegaSD / None |
genesis_plus_gx_add_on |
auto / sega/mega cd / megasd / none |
| Cartridge Lock-On | Disabled ✅ / Game Genie / Action Replay (Pro) / Sonic & Knuckles |
genesis_plus_gx_lock_on |
disabled / game genie / action replay (pro) / sonic & knuckles |
| Core-Provided Aspect Ratio | Auto ✅ / NTSC PAR / PAL PAR / 4:3 / Uncorrected |
genesis_plus_gx_aspect_ratio |
auto / NTSC PAR / PAL PAR / 4:3 / Uncorrected |
| Borders | Disabled ✅ / Top/Bottom / Left/Right / Full |
genesis_plus_gx_overscan |
disabled / top/bottom / left/right / full |
| Hide Master System Side Borders | Disabled ✅ / Left Border Only / Left & Right Borders |
genesis_plus_gx_left_border |
disabled / left border / left & right borders |
| Game Gear Extended Screen | Disabled ✅ / Enabled |
genesis_plus_gx_gg_extra |
disabled / enabled |
| Blargg NTSC Filter | Disabled ✅ / Monochrome / Composite / S-Video / RGB |
genesis_plus_gx_blargg_ntsc_filter |
disabled / monochrome / composite / svideo / rgb |
| LCD Ghosting Filter | Disabled ✅ / Enabled |
genesis_plus_gx_lcd_filter |
disabled / enabled |
| Interlaced Mode 2 Output | Single Field ✅ / Double Field |
genesis_plus_gx_render |
single field / double field |
| Frameskip | Disabled ✅ / Auto / Manual |
genesis_plus_gx_frameskip |
disabled / auto / manual |
| Frameskip Threshold (%) | 15 / 18 / 21 / 24 / 27 / 30 / 33 / 36 / 39 / 42 / 45 / 48 / 51 / 54 / 57 / 60 |
genesis_plus_gx_frameskip_threshold |
15 / 18 / 21 / 24 / 27 / 30 / 33 ✅ / 36 / 39 / 42 / 45 / 48 / 51 / 54 / 57 / 60 |
| Master System FM (YM2413) | Auto ✅ / Disabled / Enabled |
genesis_plus_gx_ym2413 |
auto / disabled / enabled |
| Master System FM (YM2413) Core | MAME ✅ / Nuked |
genesis_plus_gx_ym2413_core |
mame / nuked |
| Mega Drive / Genesis FM | MAME (YM2612) ✅ / MAME (ASIC YM3438) / MAME (Enhanced YM3438) / Nuked (YM2612) / Nuked (YM3438) |
genesis_plus_gx_ym2612 |
mame (ym2612) / mame (asic ym3438) / mame (enhanced ym3438) / nuked (ym2612) / nuked (ym3438) |
| Sound Output | Stereo ✅ / Mono |
genesis_plus_gx_sound_output |
stereo / mono |
| Audio Filter | Disabled ✅ / Low-Pass |
genesis_plus_gx_audio_filter |
disabled / low-pass |
| Low-Pass Filter % | 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 ✅ / 65 / 70 / 75 / 80 / 85 / 90 / 95 |
genesis_plus_gx_lowpass_range |
5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 |
| PSG Preamp Level | 0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 / 105 / 110 / 115 / 120 / 125 / 130 / 135 / 140 / 145 / 150 ✅ / 155 / 160 / 165 / 170 / 175 / 180 / 185 / 190 / 195 / 200 |
genesis_plus_gx_psg_preamp |
0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 / 105 / 110 / 115 / 120 / 125 / 130 / 135 / 140 / 145 / 150 / 155 / 160 / 165 / 170 / 175 / 180 / 185 / 190 / 195 / 200 |
| FM Preamp Level | 0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 ✅ / 105 / 110 / 115 / 120 / 125 / 130 / 135 / 140 / 145 / 150 / 155 / 160 / 165 / 170 / 175 / 180 / 185 / 190 / 195 / 200 |
genesis_plus_gx_fm_preamp |
0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 / 105 / 110 / 115 / 120 / 125 / 130 / 135 / 140 / 145 / 150 / 155 / 160 / 165 / 170 / 175 / 180 / 185 / 190 / 195 / 200 |
| CD-DA Volume | 0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 ✅ |
genesis_plus_gx_cdda_volume |
0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 |
| PCM Volume | 0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 ✅ |
genesis_plus_gx_pcm_volume |
0 / 5 / 10 / 15 / 20 / 25 / 30 / 35 / 40 / 45 / 50 / 55 / 60 / 65 / 70 / 75 / 80 / 85 / 90 / 95 / 100 |
| Light Gun Input | Light Gun ✅ / Touchscreen |
genesis_plus_gx_gun_input |
lightgun / touchscreen |
| Show Light Gun Crosshair | Disabled ✅ / Enabled |
genesis_plus_gx_gun_cursor |
disabled / enabled |
| Invert Mouse Y-Axis | Disabled ✅ / Enabled |
genesis_plus_gx_invert_mouse |
disabled / enabled |
| Remove Per-Line Sprite Limit | Disabled ✅ / Enabled |
genesis_plus_gx_no_sprite_limit |
disabled / enabled |
| Enhanced per-tile vertical scroll | Disabled ✅ / Enabled |
genesis_plus_gx_enhanced_vscroll |
disabled / enabled |
| Enhanced per-tile vertical scroll limit | 2 / 3 / 4 / 5 / 6 / 7 / 8 ✅ / 9 / 10 / 11 / 12 / 13 / 14 / 15 / 16 |
genesis_plus_gx_enhanced_vscroll_limit |
2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12 / 13 / 14 / 15 / 16 |
| CPU Speed | 100% ✅ / 125% / 150% / 175% / 200% |
genesis_plus_gx_overclock |
100% / 125% / 150% / 175% / 200% |
| System Lock-Ups | Enabled ✅ / Disabled |
genesis_plus_gx_force_dtack |
enabled / disabled |
| 68K Address Error | Enabled ✅ / Disabled |
genesis_plus_gx_addr_error |
enabled / disabled |
| CD access time | Enabled ✅ / Disabled |
genesis_plus_gx_cd_latency |
enabled / disabled |
| PSG Tone Channel 0 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_psg_channel_0_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| PSG Tone Channel 1 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_psg_channel_1_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| PSG Tone Channel 2 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_psg_channel_2_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| PSG Tone Channel 3 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_psg_channel_3_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 0 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_0_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 1 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_1_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 2 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_2_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 3 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_3_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 4 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_4_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Mega Drive / Genesis FM Channel 5 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_md_channel_5_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 0 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_0_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 1 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_1_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 2 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_2_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 3 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_3_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 4 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_4_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 5 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_5_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 6 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_6_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 7 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_7_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
| Master System FM (YM2413) Channel 8 Volume % | 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 ✅ |
genesis_plus_gx_sms_fm_channel_8_volume |
0 / 10 / 20 / 30 / 40 / 50 / 60 / 70 / 80 / 90 / 100 |
¶ 
External links
- Source code used: https://github.com/libretro/Genesis-Plus-GX/
- Libretro documentation: https://docs.libretro.com/library/genesis_plus_gx/