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Sega CD

The Sega CD is an addon device for the Sega Genesis that will allow the user to both play audio CDs and specially designed game CDs. It also has CD+G capabilities.

The development of the Sega CD was top secret; game programmers didn't know what they were designing for until the Sega CD was finally revealed at Tokyo Toy Show in Japan. The Sega CD was desgned to be in competition with the Turbografx-16[?], which had a CD module, not the Super Nintendo Entertainment System. The Sega CD was first released in Japan in 1991 where it was called the "Mega-CD." Initially, it was a great success because of the inherent advantages of CDs (high storage space and low media cost) and the fact that it had a nice RPG base.

The Sega CD was first released in the U.S in November 1992 for $299. Several titles were available at launch including the controvesial Night Trap. A total of 149 games have been released for the Sega CD in the U.S. Game production was mostly discontinued from 1995-1996. The Sega CD floundered in the USA, partly due to the cost. There just was not a great enough value for the price. Tangibly, game quality was little improved. The sound was often better if it included a CD audio track, but for the most part, conventional games looked the same. Sega insisted on licensing and producing primarily "full motion video" games similar to earlier laserdisc games, that were universally panned by game reviewers. The single speed CD drive added load times to all games, and the 64-color graphics and underpowered processor (for video rendering) made the full-motion games look terrible. Worst of all, they simply no fun to play. Sega wanted to showcase the power of the Sega CD, and so focused on the "FMV" games rather than importing "extended" games that only expanded ordinary games by taking advantage of the extra storage space of the CD media. Perhaps if the quality of the motion video games were better, this plan might have succeeded.

The Sega CD exists in the following models:

  • Sega CD I (Mega CD I in Japan)
  • Sega CD II (Mega CD II in Japan) had a faster CD-ROM drive
  • JVC X Eye (Wondermega) in Japan only, was a all-in one Sega CD unit
  • Sega CDX
  • Pioneer LaserActive Sega CD module, an add-on device you could add to a Laseractive Pioneer Laserdisc player.

What it adds to the Genesis:

  • 10 extra sound channels to complement the sound from the Genesis Z80 sound processor.
  • sprite enhancement features such as scaling and rotation, similar to that of the SNES Mode 7.


Main CPU: Motorola 68000 @ 12.5 MHz

  • Same as the Genesis... runs with it... except the Genesis CPU runs at the slower clock speed: 7.9 MHz
Graphics Processor: Custom ASIC RAM:
  • 6 Mbit Main RAM
  • 512 Kbit PCM Waveform Memory
  • 128 Kbit CD-ROM data cache memory
  • 64 Kbit Internal Backup RAM
  • Originally 64, same as Genesis
  • Using programming tricks, can get 128 colors via HAM "Hold and Modify"
  • Using Cinepak and TruVideo:
    • 128 to 256 colors
    • Increase screen size from 1/4 to full
    • Advanced compression scheme
    • Software-based upgrade
Storage capability
  • Approximately 500 MB of data (62 min of audio data equivalent)
  • 1/4 screen B/W footage video: 1.5 to 4 hours
  • 1/4 screen color footage: 45 minutes
  • Above specs are prior to compression
Transfer rate of Sega CD: 150 kbytes/sec (1X) Boot ROM:
  • 1 Mb contains:
    • CD Game Bios
    • CD Player Software
    • CD+G Software

   Bios Version     Machine
       1.00         Original Mega CD
       1.10         Original Sega CD, Motorized Drive
       2.00         Sega CD2/Mega CD2
       2.05         Sega CD2
       2.10         Sega CD2
       2.21         Sega CDX

Access time: 800 ms Sound Circuitry:

  • PCM Sound
    • Stereo: 8 channels
  • 32 KHz Maximum sampling wavelength
  • 16 Bit D/A converter
  • 8X internal over-sampling digital filter
  • Frequency Range: 20Hz - 20 KHz
  • Signal-to-Noise Ratio: >900dB @ 1K
  • Channel Separation: >900 dB
Output: RCA Pin Jack x2 (L/R) Dimensions: 301mm x 212.5 x 112.5 Weight: 3.1 lbs

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