The Atari Jaguar CD or Jag CD is a CD-ROM peripheral for the Atari Jaguar video game console.

Atari announced a CD-ROM drive for the Jaguar before the console's November 1993 launch. Code-named the Jaguar II during development, the Jaguar CD was released on September 21, 1995. The device sits atop the Jaguar console, fitting into the ROM cartridge slot. The drive has its own cartridge slot to allow cartridge games to be played without removing the CD drive, and to run software that used cartridge and CD in tandem. There was a separate "Memory Track" cartridge for storing saved game positions and high scores.

The Jaguar CD unit featured a double-speed (2×) drive and built-in VLM (Virtual Light Machine). Using a spectrum analyzer, the VLM provided a sophisticated video light show when an audio CD was played in the machine. Packaged with the drive were two games (Blue Lightning and Vid Grid), a music CD (Tempest 2000 soundtrack), and a Myst demo disc. Also, the startup screen is different from that of the cartridge-based Jaguar: using the VLM banks it creates a random "light show" that is different every time the console was switched on.

Source: Wikipedia