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The Mega-CD (メガCD), also known as the Sega CD, is an add-on device for the Mega Drive released in Europe, Australia, New Zealand, North America, and Japan. The system allowed the user to play games, audio CDs, and CD+G CDs.

The development of the Sega CD was confidential; game developers were not made aware of what exactly they were working on until the add-on was finally revealed at the Tokyo Toy Show in Japan. The Sega CD was designed to compete with the TurboGrafx-16 PC Engine (TurboGrafx-16) in Japan, which had a separate CD-ROM drive.

The Sega CD was not meant to compete with the Super Nintendo. This posed a problem in the markets outside of Japan, where the PC Engine did not fare very well, and the expectation was that the Mega-CD would be in competition with Nintendo.

The first version of the system sat under the Genesis console and loaded CDs via a motorized tray. The second version of the system, dubbed Sega CD 2, had the CD-ROM drive relocated to the right of the Sega Genesis system, changed to a top-loading CD-ROM drive with a lid, and was meant primarily to be used with the redesigned Genesis Core System 2. However the original model of the Sega Genesis could still be used with the addition of an extension that allowed the system to firmly sit on the add-on without overhanging the edge (the Sega Genesis still sat on top of the system, but to a much lesser extent than before).



The Mega-CD was released first in Japan on December 12, 1991. Its retail price was about ¥49,800. Initially, it was a great success because of the inherent advantages of CDs (high storage capacity and the low cost of media).

Despite having been on sale for over 2 years by March 1994, the MEGA-CD had only sold 380,000 units[1] in Japan, which meant that only 11% of Japanese Mega Drive owners had purchased the add-on unit.

North America

Sega of Japan did not speak to Sega of America about their Sega CD plans for that market until a few months later.

The Sega CD had been announced at the Chicago CES on January, 1992. Early reports had suggested that hardware in the system would allow it to display more on screen colors (from a larger palette) than the Sega Genesis or the Super Nintendo, which was an important technical concern for consumers.

In the end, the Sega CD was unable to convince North American gamers, mostly due to the cost of the console, and the lack of any hardware advancements. Many people felt there was not enough value for the price. Moreover, the game experience was little improved. Players came to have high expectations for the add-on, and Sega even promised that the Sega CD would allow a higher color palette than the Genesis. However, the end result was somewhat lackluster compared to expectations. Graphically, most games ended up looking not much better than normal Sega Genesis games, though the sound quality was higher, owing to the CD format of the games.


In Europe the Mega-CD was thought to be overpriced. It was released in April, 1993 in the United Kingdom for £270. Unlike the Mega Drive, which was a very successful console in Europe, only 60,000 of the 70,000 Mega-CDs shipped to Europe were sold by August 1993.[source needed]

Some European countries (Spain, for instance), would not get the original Mega-CD, but the Mega-CD 2, which also slowed sales.[source needed]


The Mega-CD was released on April 19, 1993 in Australia.


The Sega CD 2 was launched in the Brazilian market exactly at the same time of the U.S. release. Since the original Sega-CD was never released there, it was simply called "Sega-CD". However, because several Mega-CD units imported from Japan were already in the market, it was informally known as "Mega-CD". It was manufactured locally by Tec Toy.


Sega wanted to showcase the power of the Mega CD, and so focused on "FMV" games rather than taking advantage of the extra storage space of the CD media. Sega insisted on licensing and producing primarily "full motion video" games similar to earlier Laserdisc games, that were universally panned by game reviewers. The limited 64-color palette of the system, combined with the processor not being well-suited for video, did not lend itself well to reproducing video, resulting in grainy video in most games.

Another criticism of the software library was that most titles consisted of Shovelware, in which a developer takes an existing title and adds minor new content (usually a CD audio soundtrack, or video sequences) while not expanding the original game itself. Few titles received major changes, but three exceptions were  Earthworm Jim which featured additional levels and game changes, The Terminator and The Amazing Spider-Man vs. The Kingpin, which featured many changes, which drastically restructured the game, making it less linear, and adding animated cut scenes.

Despite a somewhat lackluster library of games, the console introduced very famous franchises. The Lunar series, which despite the relatively narrow circulation the two titles on the Mega CD received, went on to be critically acclaimed and became a cult classic, with both games receiving remakes for the PlayStation and Sega Saturn in the late 90's; and a prequel to the series for the Nintendo DS in 2005. The English publisher of the two Lunar titles, Working Designs, also published another RPG for the platform, entitled Vay. While it received generally positive reviews, the game did not obtain the same popularity as the Lunar titles. Working Designs also published Popful Mail for the Mega CD. Another notable title was the cult-classic Snatcher, a cyber-punk digital comic released by Konami and designed by Hideo Kojima and the only version of the game released in English.

One exclusive game that was published for the Mega CD is the now famous Sonic the Hedgehog CD, or Sonic CD. Sonic CD is praised for having good graphics, superior CD quality sound to the Genesis games, and an innovative style of stages, having four versions of each of the three zones in each stage. Many fans praise the game as the best of the series for these reasons.


The following models were released:

  • Sega CD I (Sega Mega-CD I)
  • Sega CD II (Sega Mega-CD II). Designed for the Genesis (second model) / Mega Drive 2 and to reduce manufacturing costs
  • X'Eye (JVC Wondermega), was an all-in-one Genesis/Sega CD unit
  • Sega CDX (called Multi-Mega outside of North America). A portable CD player that plays both Genesis and Sega CD games, as well as audio CDs, and CD-G discs. Resembling a slightly longer version of the typical portable CD player of the day.
  • Pioneer LaserActive Sega CD module, an add-on device available for the LaserActive system

Full technical specifications

The Sega CD specifications were as follows:[2]


The main CPU is a 12.5 MHz 16-bit Motorola 68000 processor. The Mega Drive/Genesis has the same processor, but at a lower clock rate of 7.67 MHz (NTSC) / 7.61 MHz (PAL).


  • Graphics Processor: Custom ASIC
  • Number of simultaneous colors on screen: 64 out of 512
  • Display resolution: 320 x 224 pixels and 256 x 224, video size from ¼ to full screen
  • Advanced compression scheme
  • Software-based upgrade
  • Scaling and rotation effects


  • Main RAM: 6 Mbit
  • PCM samples: 512 kbit
  • CD-ROM data cache: 128 kbit
  • 64 kbit Internal Backup RAM


  • 500 MB CD-ROM discs (equivalent to 62 minutes of audio data)
  • ¼ screen B/W footage video: 1.5 to 4 hours
  • ¼ screen color footage: 45 minutes
  • CD-ROM drive transfer rate: 150 kB/s (1x)

(Above specs prior to compression)


  • Size: 1 MBit
  • Used for games, CD player, CD+G and karaoke
  • Access time: 800 ms
BIOS Revisions
BIOS VersionMachine
1.00Original Sega Mega-CD (Europe/Japan)
1.02Pioneer LaserActive Mega LD (Japan/North America) (based on ver. 0.98 proto Sega Mega-CD BIOS)
1.10Original Sega CD (North America)
2.00Mega-CD 2 (Europe/Japan), Sega CD 2 (North America)
2.11Mega-CD 2 (Europe/Japan), Sega CD 2 (North America)
2.21Sega Multi-Mega (Europe/Japan), Sega Genesis CDX (North America)


The Mega-CD adds 10 extra sound channels to the Genesis's YM2612 and SN76489 using the Ricoh RF5C164 chip

  • Sound format: Stereo PCM
  • Clock frequency of source: Up to 12 MHz
  • Sound channels: 8
  • Maximum sample rate: 32 kHz (44.1 kHz for CD-DA)
  • Wave data width: 8 bits
  • 16 bit DAC
  • 8x internal over-sampling digital filter
  • Frequency Range: 20 Hz - 20 kHz
  • Signal-to-Noise Ratio: > 90.0 dB @ 1K
  • Channel Separation: > 90.0 dB
  • Output: RCA stereo Pin Jack x2 (L/R) / SCART cable
  • Mixing Input Port for sound on the original Sega Mega Drive / Sega Genesis Model via the RCA jacks on the back of the Sega CD unit.


  • Dimensions: 301 mm × 212.5 mm × 112.5 mm
  • Weight: 1.4 kg (3.1 lb)


  • Few accessories were released for the Sega CD. The most notable being an external memory card that came in the form of a Genesis cartridge. Titled the CD Backup RAM Cart, it was placed in the Genesis slot like a normal Genesis game, and the Sega CD would detect this cartridge upon booting up. Games could either be saved directly to it (on the titles that supported it) or to copy/transfer game saves to and from the Sega CD's internal RAM. Complete backups were possible as the CD Backup RAM Cart contained 16 times the amount of RAM as the Mega-CD (1 Mbit, or 2000 Game Save Blocks, compared to the Mega-CD's 64Kb, or 125 Game Save Blocks.)
  • A Light gun named "The Justifier" was also released bundled with Lethal Enforcers.
  • A multi-functional cartridge called "Megacart" was released in 2006. It works as a region converter, RAM cart and can flash cart games.

Graphic trivia

While the system was in development, several US video game magazines such as Electronic Gaming Monthly and Gamepro had published reports that the Sega CD was going to be able to display more on-screen colors than the Sega Genesis. It appears that there had been some discussion about upgrading the hardware in the Sega CD to compete with the color capabilities of the Super Nintendo, but it was vetoed.

A common myth surrounding the Mega-CD is in regard to the number of colors it can display on-screen. Like the unexpanded Mega Drive/Genesis, the published specifications of the Sega CD indicate that the system can produce up to 64 colors on-screen out of a global palette of 512 (the same color palette of the Mega Drive). However, many people claim that some games, such as Snatcher, Jurassic Park and Eternal Champions: Challenge From The Dark Side, exceeded the on-screen limit with the use of programming tricks, achieving 112, 192, even 256 colors simultaneously. Some versions of this rumor claim that there was a version of the Cinepak video codec that could render FMV in 256 colors on the Sega CD as well.

The idea of displaying more than 64 colors at once in Sega CD games is not groundless. What is not widely realized, however, is that the Sega CD breaks this limit with the same methods that can be executed on an unexpanded console, and also that these methods are all severely limited in practical use.

The most common way of displaying extra colors is with the use of raster effects, which involve simply changing the on-screen color palette in between TV scanlines as the picture is being drawn. Sonic games use this to make underwater effects. A lesser known trick is to use the priority bit of a pixel for color purposes, allowing any color to have 3 shades (normal, bright and dim) and effectively tripling the number of colors available onscreen. However, this trick compromises the video display processor's capabilities so drastically that it was rarely ever used, especially for in-game graphics. Finally, many developers simply relied on dithering, a simple artist's method of drawing pixels of two similar colors in an alternating, checkerboard-like manner, and relying on the inaccuracy of composite or RF video signals to blend the colors together into a third color. On a side note, this same method could be used to make a fake transparency just by leaving every other pixel blank.

The programming trick which many mistakenly believe can be used to display extra colors on the Sega CD is called HAM, or Hold And Modify. This complicated trick was used with the Commodore Amiga line of computers with the same goal of raising the on-screen color limit. However, the Amiga could also use raster effects, and this is where the confusion most likely started. At some point, it was probably said that a trick similar to one used on the Amiga could be used with the Sega CD to display extra colors on-screen. Since people knew there was a trick to get extra colors out of the Amiga called HAM, they may have then assumed that the Mega-CD could use HAM as well. However, the Sega CD has no support for this or a similar function at all whereas the Amiga's graphic chip was designed for it.

Mega Drive/Genesis titles re-appearing on CD

Several Mega Drive/Genesis titles (As well as franchises appearing on other platforms) were ported to Sega's CD format. The CD counterparts usually offered reworked soundtracks, and slightly improved graphics. Some of these titles and their differences:
  • After Burner III - A port of the Japanese arcade game Strike Fighter. This particular title does feature a hard-rock/heavy-metal re-produced soundtrack of the majority of the original After Burner/After Burner II music.
  • Batman Returns - One of the more lengthy ports. The game features the full side-scrolling game of Batman Returns from the Mega Drive/Genesis, as well as new driving action stages in between each side-scrolling hub. An original soundtrack created by Spencer Nilsen (Ecco the Dolphin) features many dark symphonic tunes mixed with batches of rock/heavy-metal. The new driving modes show off much of the Sega CD's added power with big sprites and a lot going on with little slowdown.
  • Brutal: Paws of Fury - The Sega CD version of this animal-based fighting game added two new intros, new CD soundtrack, two new characters, new voice clips, smoother animation, and a Bonus section in the main menu. The bonus section had an "Outtakes" video, a sound test, and other information.
  • Columns - appeared as part of the Sega Classics Arcade Collection and featured a new soundtrack.
  • Chuck Rock - A direct gameplay port. Visuals come out as a little bit smoother than other versions, and the game includes a re-produced CD soundtrack.
  • Chuck Rock 2: Son of Chuck - Title includes a re-done CD soundtrack as well as FMV intro and ending video sequences, detailing the storyline.
  • Earthworm Jim: Special Edition - This direct port of the PC game also doubles as a music CD.
  • Ecco the Dolphin - A direct port of the Genesis/Sega Mega Drive game. There are no differences in gameplay, visuals, or sound effects, except for some new levels. The soundtrack is, however, a completely new symphonic work by Spencer Nilson. The disc doubles as a music CD.
  • Ecco: The Tides of Time - A direct port of the Genesis/Mega Drive game with a re-vamped CD soundtrack and lengthy CG sequences illustrating the story throughout the game. Disc doubles as a music CD.
  • Eternal Champions: Challenge from the Dark Side - More of a full-on sequel to the original Eternal Champions. With all of the enhancements and editions (Characters, fatalities, CG sequences, re-worked soundtrack and fresh story elements), it should not be confused as a direct port.
  • Final Fight CD - Up until Final Fight was re-released in the recent Capcom Classics collections for PlayStation 2, XBOX, and PSP, the Sega/Mega CD version of the game offered the most-complete experience. Guy is a playable character, the game takes advantage of the Sega CD's added power with smoother animation than other previous ports (SNES/SFC), and also incorporates simultaneous two-player gameplay, along with extended intro and ending sequences and a revamped musical score with real instruments on a CD-Player-Friendly soundtrack. A time-attack mode is also available, where one or two players are pitted against as many enemies as they can handle within a defined amount of time.
  • Flashback: The Quest for Identity - A port of the PC game. Includes all CG FMV sequences and each stage now features its own full-length, CD-quality music track (versus the short music clips that played sparsely throughout the game in the original PC game and console ports).
  • Golden Axe - appeared as part of the Sega Classics Arcade Collection and featured a new soundtrack.
  • Heart of the Alien - A port of Out of This World, which originally debuted on the Amiga, PC, Mega Drive, and SNES. Sega CD version includes smoother animation and quicker gameplay overall with less slowdown, a revamped CD soundtrack, as well as the full sequel, Out of This World 2: Heart of the Alien.
  • Lethal Enforcers - Identical to the earlier console ports, although it includes the full arcade soundtrack, as well as small video clips. A lightgun bundle was released.
  • Mickey Mania: The Timeless Adventures of Mickey Mouse - The Sega CD version is identical gameplay-wise to the Genesis version, but includes additional voice clips for Mickey, smoother animation, and a full Redbook CD soundtrack. The final boss also had to be fought twice to truly defeat him in the Sega CD version.
  • Mortal Kombat - The Mega CD version features the full arcade soundtrack with remixes of the MK Movie soundtracks, more graphical details (Including blood, heads, and bodies in the pit stage), and an FMV intro derived from the original MK TV commercial.
  • NBA Jam - The most complete port of the arcade game, the title features an FMV ending, as well as the full arcade CD soundtrack. Game data is stored via the Sega CD's internal memory backup.
  • Pitfall: The Mayan Adventure - A direct port of the Mega Drive/Genesis game, with FMV intro and a CD soundtrack.
  • Prince of Persia - Includes anime-styled FMV sequences, a full CD soundtrack, and the ability to save your progress via internal memory, as well as the option to increase or decrease the games speed/framerate.
  • Streets of Rage - appeared as part of the Sega Classics Arcade Collection.
  • Wolfchild - Some differences (better than the original Mega Drive version) to the level design and a new CD quality Soundtrack.

External links

  • Sega-16 - Comprehensive site with hundreds of reviews and articles.
  • SegaBase - Comprehensive history of this system This page uses content from Wikipedia. The original article was at Sega Mega-CD. The list of authors can be seen in the page history. As with Sega Wiki, the text of Wikipedia is available under the GNU Free Documentation License.

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  1. Template:Cite news
  2. Schiller, Christian (1998-12-06). Sega CD programming FAQ (plain text, 7bit ascii). Retrieved on 2006-09-03.