¶ Technical data
- Manufacturer: Sega
- Year of release: 1991
- Units sold: 2.24 millions
- Iconic game: Sonic CD
- CPU: Motorola 68000 @ 12.5 MHz (in addition to the Mega Drive's own 68000)
- RAM: 768 KB of program RAM, 256 KB of PCM RAM, 64 KB CD buffer
- Video: dedicated ASIC handling sprite rotation and scaling
- Sound chip: Ricoh RF5C164 (8 PCM channels) + CD audio playback
- Media: CD-ROM (single speed drive)
¶ Presentation
The Mega-CD (Sega CD in North America) is a Mega Drive add-on launched on December 12, 1991 in Japan, in 1992 in the United States and in 1993 in Europe. It is not a standalone console: the unit connects under or beside the Mega Drive and brings it a CD-ROM drive, a second 68000 processor, extra memory and a chip able to rotate and scale sprites in real time.
Its main selling point is CD support: CD-quality soundtracks, digitized video cutscenes and games far larger than what cartridges allowed. Expensive and released just as the market was about to move to 3D, the add-on never went beyond 2.24 million units and remains one of Sega's major commercial failures.
Its library, often reduced to its Full Motion Video games (Night Trap, Sewer Shark, Ground Zero Texas), nevertheless contains genuine highlights: Sonic CD, Lunar: The Silver Star and its sequel, Snatcher, Popful Mail, Final Fight CD and Silpheed. Many titles use the rotation/zoom chip for effects impossible on a plain Mega Drive.
¶ Emulators
Emulator availability per board:
| Emulator | RPI3/RPI02W | RPI4/400 | RPI5/500 | OGA/OGS/RG351 | PC | RG353 |
|---|---|---|---|---|---|---|
| Libretro picodrive | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ |
| Libretro genesisplusgx | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ |
The default emulator is picodrive, very fast and available on every board including RPi3 and RPi Zero 2. genesisplusgx is the alternative: high compatibility and CRT output support.
Both cores support netplay. Softpatching is available on neither of them. RetroAchievements are available on this system, and a light gun is recommended for the machine's shooting games (the Lethal Enforcers series in particular).
¶ BIOS
The three regional BIOS files are mandatory: without the BIOS matching the game's region, the game will not boot. File names must be respected exactly.
| File name | Description | MD5 | Emulators |
|---|---|---|---|
bios_CD_E.bin |
Europe Mega-CD BIOS (mandatory) | e66fa1dc5820d254611fdcdba0662372 | picodrive, genesisplusgx |
bios_CD_U.bin |
US Sega CD BIOS (mandatory) | 2efd74e3232ff260e371b99f84024f7f | picodrive, genesisplusgx |
bios_CD_J.bin |
Japan Mega-CD BIOS (mandatory) | 278a9397d192149e84e820ac621a8edd or bdeb4c47da613946d422d97d98b21cda | picodrive, genesisplusgx |
Two MD5 values are accepted for
bios_CD_J.bin:278a9397d192149e84e820ac621a8eddandbdeb4c47da613946d422d97d98b21cda, which correspond to two revisions of the Japanese BIOS. Either one works.
Place your BIOS files like this:
/recalbox/share/bios/segacd/
├── bios_CD_E.bin
├── bios_CD_U.bin
└── bios_CD_J.bin
The folder is indeed named
segacd(the system's internal name), notmega-cdormegacd. Recalbox also declares these three files on the Mega Drive platform: do not duplicate them, a single copy inbios/segacd/is enough.
¶ Roms
Put your games in:
/recalbox/share/roms/segacd/
Supported extensions per emulator:
| Emulator | Extensions |
|---|---|
| picodrive | .chd .cue .iso .m3u |
| genesisplusgx | .chd .cue .iso |
Images in Redump format are strongly recommended. The .chd format is the most convenient: a single compressed file containing both the data tracks and the CD audio, which matters for the many Mega-CD games whose music sits on CD tracks.
For the few games spread over several discs, create an
.m3ufile listing the images in order — supported by picodrive only.
A .cue file with its .bin/.wav tracks also works, but always keep the .cue and its tracks in the same folder.
Also have a look at the Mega CD — MSU-MD games guide for game preparation, configuration and system-specific tips.