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Mega Drive

Mega Drive icon Mega Drive logo

Overview

The Sega Mega Drive (Genesis in North America) is a 16-bit console that debuted in Japan on October 29, 1988, then in the US and worldwide shortly after. Built on a Motorola 68000 main CPU with a Zilog Z80 co-processor, it delivered arcade-like performance and remains a beloved part of the genesis/megadrive system groups in REG-Linux.

Technical specifications

  • CPU: Motorola 68000 at 7.67 MHz with a Zilog Z80 at 3.58 MHz for sound and backwards compatibility
  • Memory: 64 KB main RAM, 64 KB video RAM, 8 KB audio RAM for the YM2612
  • Display: 320×224 resolution with up to 61 colors on-screen (out of 512)
  • Sound: Yamaha YM2612 FM synthesizer plus Texas Instruments SN76489 PSG

Quick reference

  • ROM folder: /userdata/roms/megadrive
  • Accepted ROM formats: .bin, .gen, .md, .sg, .smd, .zip, .7z
  • Emulators: RetroArch (libretro: GenesisPlusGX, libretro: GenesisPlusGX-wide, libretro: Picodrive, libretro: blastem), MAME (for specialized ports), CLK (Clock Signal)
  • System group: genesis, megadrive

BIOS

Most Mega Drive/Genesis emulators do not require BIOS files. The only exceptions are Master System/Game Gear compatibility layers (handled under those systems).

ROMs

Keep cartridge images such as .bin, .gen, .md, .sg, .smd plus zipped collections inside /userdata/roms/megadrive. Some cores also accept .gg/.sms for Game Gear/Master System when appropriate. Disc-based formats (.iso, .cue + .bin, .chd) belong to the Sega CD documentation instead.

Region

Mega Drive systems use region-specific PAL/NTSC timing. PAL titles run at 50 Hz and can appear slow on modern displays; some games offer a built-in region mode. To play PAL titles at the correct speed:

  1. Set your display’s refresh rate to 50 Hz in the advanced options for the game or through the display configuration helper.
  2. Use RetroArch’s Quick Menu ([HOTKEY] + south face button) to change Region to pal.
  3. Save the override so the setting persists.

Some displays require xrandr or custom monitor profiles to expose 50 Hz modes; see /display_issues#display_issues_when_xrandr_is_your_friend for troubleshooting.

Emulators

RetroArch

RetroArch hosts the Mega Drive cores. The Quick Menu adjusts shaders, hotkeys, controller mappings and per-game overrides. REG-Linux surfaces many of these options through EmulationStation menus as well.

Standard retro settings: megadrive.videomode, megadrive.ratio, megadrive.smooth, megadrive.shaders, megadrive.pixel_perfect, megadrive.decoration, megadrive.game_translation, megadrive.audio_latency, megadrive.video_threaded.

ES setting name REG-Linux.conf_key Description & values
GRAPHICS BACKEND megadrive.gfxbackend Choose OpenGL (opengl) or Vulkan (vulkan).
AUDIO LATENCY megadrive.audio_latency Buffer size in milliseconds: 256, 192, 128, 64, 32, 16, 8. Increase if you hear crackles.
THREADED VIDEO megadrive.video_threaded Use a second thread for rendering (true On, false Off).

libretro: GenesisPlusGX

GenesisPlusGX is the high-accuracy workhorse that covers Mega Drive/Genesis, Master System, and Game Gear. It supports NTSC filters, FM chip toggles, controller types per port, Game Gear LCD ghosting and more. See megadrive_controller_mapping_3b.png / megadrive_controller_mapping_6ba.png etc. for reference overlays.

libretro: GenesisPlusGX-wide

Widescreen-patched version of GenesisPlusGX; draws extra columns to create a 16:9 picture at the cost of compatibility. Use with caution on titles that support widescreen patches.

libretro: Picodrive

Lightweight Sega 8-bit core that also targets Pico/32X hardware; ideal for SBCs.

libretro: blastem

Cycle-accurate Genesis core with few extra configuration options. It is recommended when accuracy matters and your hardware can keep up.

CLK

CLK (Clock Signal) is a low-latency multi-system emulator included since REG-Linux 42. It provides an alternative path for playing Mega Drive, Master System and other 8/16-bit systems.

Controls

Here are the default Mega Drive/Genesis controls shown on a REG-Linux Retropad:

megadrive controller overlay

Additional mapping references for 3-button/6-button pads and Master System controllers remain available in the repository (see mastersystem_controller_mapping.png, etc.).

Troubleshooting

For more help, consult the generic support pages. If a ROM refuses to start, double-check that you matched the correct ROMset/version to the core you are launching (e.g., 0.78+ for GenesisPlusGX, latest for libretro: mame).