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Useful Notes / Sega CD

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A Sega CD attached to the underside of a North American Model 1 Genesis.

"HEY! You still don't have a Sega CD?"
Angry Black Guy, 1994 TV spot

The Sega CD, also known as the Mega-CD in Europe and Japan, was a Compact Disc-based add-on for the Sega Genesis. As its name would suggest, it allowed the Genesis to take advantage of the higher-capacity CD-ROM storage medium, enabling features such as pre-rendered video playback (branded "Full-Motion Video") and Red Book CD sound. Unfortunately, the Genesis'/Mega Drive's own processing power wasn't quite enough to take advantage of these features to the fullest. It was released in 1991 in Japan, with North America getting it in 1992 and Europe in 1993. The launch price was $299 (£270 in Great Britain), twice of that of the Genesis itself after it was given a price cut in 1991.

The Sega CD came about because Sega heard rumors of Nintendo's deal with Sony to develop their own CD add-on, and also because NEC had just released a CD attachment for their PC Engine console (ironically, the SNES CD-ROM wound up becoming an albatross and never saw releasenote ; Sega wasted no time in mocking Nintendo for this in their ads for the Sega CD). Sega jumped the gun and pushed out their own attachment as a countermeasure: it allowed the Genesis to perform tricks similar to the SNES that would otherwise be impossible with the original hardware, such as Mode 7 effects and sprite rotation.

The add-on is probably best known for its association with Full-Motion Video games. While not the first or even last machine to host FMV games, they were prominently featured in Sega's aggressive marketing and a fairly common part of the library thanks to Digital Pictures, a major proponent of the game genre. One of these FMV games was Night Trap, which obtained infamy by being featured at a U.S. Senate hearing concerning portrayals of violence in video games and contributing to the creation of the ESRB. Hosting live action footage on a home console was impressive for the time, but it was heavily degraded by the Genesis's palette limitations and the visuals have aged poorly (the few CD games that also supported the 32X add-on don't suffer from this issue and fared much better). To quote Digital Pictures co-founder Ken Melville, "[footage was reduced to] the most horrifying, blurry, reduced-color-palette mess imaginable." The FMV games themselves also quickly gained a reputation for being shallow experiences not worth buying, which contributed to turning people away from the CD.

The Sega CD also received a number of enhanced ports of Genesis games, though many didn't have substantial changes outside of improved soundtracks and a bit of extra content. Despite ending up with a sizable library, the add-on was criticized for being improperly supported between the poorly-received FMV games and ports that didn't justify the high asking price. While completely original, non-FMV, and actually good games do exist for the Sega CD, they're very few in number and are often overshadowed by the library's poor reputation, with recognition of them being limited to the most hardcore of fans or retro enthusiasts. The only Sega CD game to break into mainstream consciousness as "good" is Sonic the Hedgehog CD, if only because of the sheer weight of the Sonic the Hedgehog brand recognition. Even then, it has become a rather divisive entry amongst the fanbase.

In addition to its tepid audience response, the Sega CD is also seen as a commercial failure, only selling 2.4 million units (compare the 30 million Sega Genesis units sold). While not as disastrous as the later 32X add-on, the lacking reception and sales were the first signs of Sega's eventual decline during the mid- and late-90s that would lead to them leaving the console hardware market. The combination of this and the PC Engine CD's poor sales outside of Japan (as the TurboGrafx-CD) are also credited as a likely factor in Nintendo choosing to stick with cartridges for the Nintendo 64 — right when CD-ROM technology became more readily practical for game developersnote . Oops.

The Sega CD is also noteworthy for how many hardware permutations it had. While you're probably familiar with either the bottom-mount Model 1 or the side-mount Model 2, there was also the Sega CDX, a much smaller unit that combined a Genesis, Sega CD, and a Walkman music player into a single unit: the console was actually small enough to double as a portable music player, and was marketed as such! Unfortunately, it had a high $300 price tag, was produced in small quantities, and its disc reading laser quickly developed a reputation for being finicky and breaking down quickly. It was also incompatible with any other Genesis add-on hardware, like the Power Base or 32X.

Another interesting version of the Sega CD is the JVC X'Eye, known as the Wondermega in Japan. This was a fully licensed console produced by JVC under agreement with Sega, and like the CDX combined a Sega Genesis and a Sega CD into a single unit. While the sound hardware produces slightly better sound and music than the Sega produced units and only uses one AC Adapter as opposed to having to use a separate brick for the Genesis and CD, its US$500 price tag (in 1994! That's about $980 in New Twenties money) meant that it was actually significantly cheaper to buy a Genesis and Sega CD separately than to buy an X'Eye, particularly after the buyer's market for the Sega CD dried up and retailers began slashing the price on the unit (a year before the Sega Saturn was released, you could buy a Sega CD for $20 at most toy stores). Nevertheless, the X'Eye's robustness as a unit and the fact it only uses one AC adapter make it highly sought after among collectors and, if you can find one, an excellent "all-in-one" unit for a Genesis collection.

Today, the Sega CD is generally understood as having had a lot of potential that was sadly never utilized by most developers, with its main stumbling blocks being the Loads and Loads of Loading, poor marketing, high launch price, and the fact that it required both a plug into the Genesis and an independent power adapter.

Another aspect of the Sega CD that went semi-memetic were the cases for its games. Instead of the standard square jewel cases used for music CDs and computer CD-ROMs, releases of Sega CD games outside of Japan used jewel cases the size of a longbox, an outer cardboard box that music CDs were packaged in before being phased out in the early '90s. These larger jewel cases were much deeper than normal models, which made them extremely fragile, and because the game discs would not sit in their mounting in the case, it also necessitated a packed-in foam sponge to hold the disc in place, which would be held in place by the case lid. This put even more stress on the case lid, and led to even more breakage. Japanese releases simply used regular jewel cases to greater success. The Sega CD was not the only system to do this — early 3DO Interactive Multiplayer and PlayStation games in the west used these cases as well, as did most western releases of Sega Saturn games — but the fact that the Sega CD used them so consistently led to the longbox-sized case becoming inextricably associated with the add-on.

Even with all that, though, the Sega CD is seen as a decent addition to any retro gaming collection due to its unique software and enhanced Genesis ports, though many of the rarer games have become extremely valuable and thus expensive to purchase secondhand.

Thankfully, SEGA is (partially) rectifying this with the Sega Mega Drive Mini 2, a followup to the Genesis/Mega Drive Mini that, in addition to more Genesis/Mega Drive games, features a number of Mega-CD titlesCurrent List of CD Titles . Its Japanese/U.S. release is currently set for October 27, 2022.



  • The sprite capabilities are identical to the Genesis/Mega Drive console, but the CD can do sprite scaling and Mode 7 effects.
  • Like the main console, the CD add-on has limited support for real time 3D, such as the main fighter and enemies in Silpheed (with the backgrounds being pre-rendered full-motion videos), Stellar Fire and the port of Starblade.


  • A Motorola 68000 chip running at 12.5 MHz. The 68000 chip already in the Genesis becomes the sound chip's CPU.


  • 512 KB of main RAM and 256 KB of video RAM.
  • 64 KB of sound RAM.
  • 16 KB of CD drive cache.
  • 8 KB of back up RAM, with memory cartridges going at 128 KB.


  • Same as the Genesis/Mega Drive, but has a extra chip that can do scaling and rotation effects like the SNES's Mode-7 chip (the SNES has 2 PPUs, 1 for modes 0 to 6, and the other for mode 7) with the DPS1 chip and playing FMV video.
  • Like later models of the TurboGrafx-CD, the Sega CD supports CD+G, a variant on the Red Book standard that enables compatible CD players to display low-resolution graphics in time with the audio. This was more useful for Japanese audiences, as CD+G could be used to display song lyrics in real time for at-home karaoke parties (CD+G never really took off anywhere else).


  • Because of the additional memory of the discs, Sega CD/Mega-CD games can play pre-recorded Red Book audio soundtracks for games. The drive also doubles as a standard CD player. Discs are multi-partitioned, with track 1 carrying game data and track 2 onwards carrying Red Book CD audio. (This also has the effect of making games that use Red Book audio playable CDs in any standard CD music player, so long as you skip to track 2!)
  • Ricoh RF5C164 note  16-bit 8 channel PCM chip running at 32 KHz (44.1 KHz for CD-DA), also its own CPU running at 12 MHz.
  • On Model 2s, the console can receive audio from the CD add-on internally and output the audio mixed. However, on Model 1 machines, a passthrough cable must be hooked into the console's headphones jack to connect it with the add-on, and audio from then must henceforth be received from the add-on instead of the console. As a result, while the Model 1 can be installed on the Sega CD/Mega-CD 2 with a base extension, the Model 2 is incompatible with the Sega CD/Mega-CD 1.


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  • Earnest Evans:
    • Earnest Evans (a Japan exclusive game which would later be ported to the U.S. Genesis, albeit in a stripped-down state)
    • Annet Futatabi





Tropes associated with the Sega CD:

  • Interactive Movie: If there is one thing people most associate with this system, it's this genre of games, especially in retrospect. A major selling point of the system was being the first major one readily capable of playing pre-rendered video footage, and the system otherwise struggled to find use for all the extra space afforded by the CD-ROM format outside of digital soundtracks. As a result, many, many, many developers jumped aboard this hype train, to often mixed or outright critically panned results.
  • Loads and Loads of Loading: Another hallmark of the system was having to wait...a lot. With only a single speed drive, even the modest capacity needs of the time took significantly longer on disc than on cartridge, leaving tons of time spent waiting for the RAM to be filled up. If you want to play a game on this system, be prepared to have your patience put to the test.
  • Pre-Rendered Cutscene: Even among the games for the system that aren't in the Interactive Movie genre, it was very common to see a game cram one of these in if it was at all possible, even if it didn't need one. Movie tie-in games were an especially big offender.
  • Take That!: The most recognizable ad is the Angry Black Man ad, quoted at the top of the page. In addition to the first quote, he continues the tradition of Sega taking potshots at their rival with "What are you waiting for, Nintendo to make one?"
  • Updated Re-release: The system's library is a bit noteworthy, for better and worse, for having a fair number of enhanced ports of Genesis games, many of which are considered the definitive versions. These games include the likes of Earthworm Jim, Mickey Mania, and Ecco the Dolphinnote . While in retrospect many enjoy this aspect, the contemporary reaction was a question of why one would bother paying so much for an add-on to play the same games with only a few enhancements (aside from Earthworm Jim, all those aforementioned games only add better audio quality and otherwise are the same game, and even the former's new content is limited to an extra level and weapon), when the Genesis version provided a near identical experience without breaking the bank.