Sega CD - The Other CD Expansion

The Sega CD is treated like the unwanted step-child of the CD expansions.  Early CD systems and expansions before the PlayStation were not the breakthrough product their manufacturers hoped they would be.  They did not deliver the substantially superior gaming experiences they promised and were generally considered too expensive for what they did deliver.  And what they delivered was often unimpressive, ports of cartridge games with enhanced audio and superfluous cutscenes, FMV games which relied on route memorization, PC game ports that had no business being run on hardware that did not have a hard drive, a keyboard or a desk with which to use a mouse and interactive entertainment software which was barely interactive and not entertaining.  Today we are going to take a look at the Sega CD, its hardware, its quirks and ultimately the games that make it worth considering as a device on which to play games rather than to put on a collector's shelf.


Outside of Japan, the Sega CD was the add-on CD console expansion with the most games.  It had more game releases than the Neo Geo CD, more than the Turbo CD, more than the CD-i and much more than the Jaguar CD.  It also had more traditional FMV games (37 according FMV World) than any other contemporary system.  This did not help its perception as an FMV-game system, nor did Sega's marketing emphasizing the full motion video at the expense of meatier games.

The Genesis was originally released in a tray-loading model, the Model 1, on top of which the Genesis sat on top.  The Sega CD was made to integrate with a Genesis Model 1, which was the only model available at the time of its design.  Then Sega released the Genesis Model 2 and thereafter redesigned the Sega CD to load discs via a simpler door lid mechanism.  This console fits the Genesis Model 2 nicely but will fit the Model 1.  A complete Sega CD Model 2 will come with a plastic spacer to extend the length of the CD unit's base to accommodate the wider footprint of the Genesis Model 1.  There is also the Sega CDX which marries the Sega Genesis and Sega CD hardware into one compact unit.  The JVC X'eye/WonderMega also does the same thing in a much larger enclosure.

For the beginning Sega CD user, there is no serious question which model you should look out for, get a Model 2.  A Model 2 has fewer moving parts, fewer motors, a simpler drive mechanism, is much easier and uses through-hole capacitors rather than the surface mounted capacitors in the Model 1.  You are much more likely to obtain a reliable Sega CD Model 2 than a Model 1.  Spacers for the Genesis Model 1 are harder to find, but the spacer really is not necessary to ensure a functioning unit.  Neither are the mounting plates, that just helps keep the console attached to be base but the friction of the expansion connector works just as well.  Just hold the Genesis down when pulling cartridges from its slot when it is attached to the Sega CD.

Using a Sega CD is surprisingly easy.  When you turn the console on and there is no cartridge in the Genesis, the Sega CD's BIOS will load.  The BIOS can detect if the door or tray is open or closed and will attempt to load any disc inserted into it.  The Sega CD can load Audio CDs, Sega CD games and CD+G discs.  CD+G discs are used mainly for karaoke releases.  The Model 2 has a button to open the CD door, but the Model 1 opens the CD tray by pressing the reset button on the Genesis.  It's a weird way to save on the cost of a button.  On the other hand, the Model 2's BIOS has this rather ominous music compared to the rather bombastic tune that the Model 1's BIOS plays.

The Sega CD uses the same power brick as a Genesis Model 1.  It also has stereo CD RCA audio jacks on the back, mainly for connecting to a stereo receiver.  This allows it to be used as a CD audio player and there are instructions in the manuals on how to use the Sega CD as an Audio player without a video display.  The Sega CD requires an audio cable to be connected from the Genesis' Model 1 Headphone Jack to the input jack on the back of the CD unit to output Genesis audio via its RCA audio jacks.  The Genesis Model 2 can output its audio via the expansion connector, so with the Sega CD it does not require any additional cabling.

Unlike the Turbo CD and the SNES CD Prototype, the Sega CD has a lot of hardware inside it.  The Turbo CD and SNES CDs were mainly CD and PCM audio streamers with a RAM buffer for data.  The Sega CD is that and much more, it has its own CPU and adds enhanced graphics.  The CPU is a Motorola 68000, but clocked much faster (12.5MHz) than the Genesis' 68000 (7.67MHz).  The graphics chip can display MPEG-1-like compressed video, perform rotation and zooming effects like the SNES Mode 7 and has support for 3D polygons.  The Sega CD, despite only having a 1x speed CD drive, loads most games pretty quickly.  The only games which it stumbles with tend to be PC ports like The Secret of Monkey Island and The Adventures of Willy Beamish.

The Sega CD did not significantly improve on the Genesis' ability to output color (typically the Genesis could display 64 colors on screen from a 512 color palette), so the emphasis on what would look like low-color FMV did the system no favors.  The Sega 32x eventually fixed the lack of colors, but only six Sega 32x CD games were (re-)released and they are all FMV games.  The Sega CD was one of the earliest systems where anime-style art was really used, and the anime-style artwork featured on several Sega CD is often very impressively detailed and well drawn.

Certain games will save games to the 8KB of backup RAM inside the Sega CD.  There is a coin-cell battery inside the system, but strangely enough the manual states that the battery backup will last about a month if the system is not turned on during that time.  Some games will require a lot of storage space and to accommodate them Sega released the CD RAM cartridge.  Storage space in the Sega CD is in blocks of 64 bytes.  The base unit provides 125 blocks, but a game like Shining Force CD will eat it all up and you need the CD RAM cartridge to finish the game..  A CD RAM cartridge contains 128KB or 2045 blocks.  Three blocks appear to be used by the formatting and file system.

The Sega CD (and Sega 32x) does introduce some small compatibility issues.  The first 4MB of the Genesis 68000 CPU's 16MB addressing space is dedicated to cartridge ROM & RAM.  The next 6MB is used by the Sega CD and Sega 32x.  If one or the other is plugged into the Genesis, then ROMs cannot use that 6MB area.  This is why Super Street Fighter II uses bankswitching technology even though it is a 5MB game.  Official software, including unlicensed games from Accolade and Wisdom tree, doesn't have compatibility issues.  Unlicensed software from Taiwan or China may have issues.  The original 2006 homebrew releases of Beggar Prince won't work with a Sega CD, but the "20th Anniversary" release will.  Certain demos over 4MB like Bad Apple won't work properly but Overwatch 2 will because it implements bankswitching.

Like other CD systems before the 5th Generation, there is no on-disc copy protection with Sega CD games.  CD replication technology had not yet become affordable for the ordinary consumer and CD-r technology was not available during most of the Sega CD's market life.  If your Sega CD has a working drive mechanism, then its entire library is open to being burnt onto a disc.  The preservation project of repute handling CD systems is redump.org and cue sheets are posted.  BIN/CUE is the format of choice for CD burning, although ISO/CUE and IMG/CUE also work fine.  Virtually all Sega CDs are mixed data/audio CDs.  Some images will come with a large BIN file and some will come with separate BIN and audio files, but as long as you have a CUE sheet, you can reconstruct a working CD.

For burning, the best program to use is imgburn.  I had no trouble burning working discs, except in one instance, using imgburn and my LG WH14NS40 and ordinary CD-rs from Sony and Memorex.  This 14x SATA Blu-ray writer burnt reliable Sega CDs at 16x speed.  My experience may have been unusually blessed.  The only time I had trouble burning a disc was when I tried to burn the Rock Sampler CD+G disc included with the Sega CD Model 1s.  I could get the Graphics portion of my images to work at first by burning the BIN/CUE.  They would only work as Audio CDs.  Then I figured out that the Graphics in CD+G are stored in the CD's subchannel data and that BIN/CUE does not preserve that data.  Once I burned it with CloneCD or an Alcohol 120% image format, the CD+G worked perfectly and showed the graphics in the Sega CD's music player screen.

While there is no copy protection on the discs, Sega CD units are region locked.  A US machine will only play US discs, a PAL Mega CD will only play PAL discs and a Japanese Mega CD will only play Japanese discs.  Any Mega EverDrive will allow you to load any CD BIOS in place of the built-in BIOS and allow you to play discs from any system.  The US library is very comprehensive, the most prominent import you will likely want to run is Sonic CD, which has different music in its Japanese and European releases.  A Mega EverDrive (except for the X3) can also act as a CD RAM cartridge, making this flash cart very useful indeed with a Sega CD.

Finally, let's talk about games, as in which ones are worth playing and which ones should you stay far away from.  Some of the best games are the exclusives or near exclusives.  Everyone should start with Sonic CD, which has an interesting time travel element and really shows off the scaling and rotation abilities of the Sega CD.  Silpheed shows off the system's 3D polygon pushing capabilities, and its almost in the Super FX class.  If you need an traditional RPG fix, Vay and the two Lunar games will fulfill your need.  While Pier Solar is not a Sega CD game, it can use the Sega CD for enhanced music with a freely downloadable CD.  Eternal Champions: Tales from the Dark Side and Final Fight CD are worthy entries in the 1-on-1 fighter and beat-em up genres, respectively.

Tactical RPGs also have a good showing on the Sega CD, Shining Force CD comprises essentially vastly enhanced port of the first two Game gear Shining Force games.  Dark Wizard is also more of a tactical RPG.  Some Sega CD ports like Out of this World (contained in Heart of the Alien), Flink and Shadow of the Beast II use 320 pixel modes where their Genesis cartridge versions used 256 pixel modes.  Some people praise Earthworm Jim and the Ecco Sega CD ports for their CD music but I like their cartridge versions' music better.  Batman Returns, Spiderman v. the Kingpin and Terminator are ports or near ports that substantially rise above their cartridge precessors.

Rounding out the library are quality shooters like Lords of Thunder, Robo Aleste and Soul Star.  Keio's Flying Squadron is an excellent cute-em up.  And then there's Popful Mail, which is a side-scrolling adventure with RPG and Metroidvania elements.  Laserdisc arcade games are reasonably represented, with Dragon's Lair, Time Gal, Road Avenger and Space Ace being decent but very unforgiving on timing.  Mansion of Hidden Souls is an interesting 7th Guest-like exclusive for the Sega CD.  The only official overseas release of the ultra violent (for its time) Snatcher is on the Sega CD.  And everyone should play such historically significant "classics" like Night Trap at least once.

If you are looking for some laughs with bad games, you are in for a treat with the Sega CD.  If you want to play a truly atrocious port of a bad game, try Mad Dog McCree, I dare you.  And if you rant to induce fits of rage, Heart of the Alien will make you want to rip someone's heart out.  FMV sports games and rail shooters?  Pass.  Then there are the "interactive entertainment titles", I guess for a lack of a better term, like the Make My Video series.  You can mine the Sega CD library and come out with gold, but you need to know what's good or you will be wasting a lot of time with terrible or poorly aged games.